Electric traction machine for a motor vehicle, and motor vehicle

Abstract

The invention relates to an electric traction machine (10) for a motor vehicle, comprising a stator (16), a rotor (18) which can be rotated relative to the stator (16) about an axis of rotation (22), a hollow rotor shaft (20) on which the rotor (18) sits for conjoint rotation and within which oil (28) can be conducted, and a housing (12) surrounding the stator (16) and the rotor (18), wherein: the rotor shaft (20) is supported on the housing (12) by means of at least one rotor shaft bearing (24); for lubrication of the rotor shaft bearing (24), an outlet opening (42) associated with the rotor shaft bearing (24) is provided in the rotor shaft (20), through which outlet opening oil (28) can exit the rotor shaft (20); a deflection element (44) is provided, by means of which the oil (28) that has exited the rotor shaft (20) can be deflected to the rotor shaft bearing (24).

Description

[0001] Electric traction machine for a motor vehicle and motor vehicle

[0002] The invention relates to an electric traction machine for a motor vehicle and a motor vehicle with an electric traction machine.

[0003] EP 1 301 977 B1 discloses a brushless electric motor with permanent magnets. The motor comprises a rotor assembly with a rotor shaft and one or more permanent magnets arranged on the rotor shaft. The motor is inserted into a stator unit, which has a stator body and field windings. Hermetic encapsulation of the rotor ensures that no foreign matter can penetrate the rotor. The rotor bearings are permanently lubricated and protected against environmental influences.

[0004] Furthermore, DE 10 2022 102 647 B3 discloses an electric machine with a stator and a rotor that can rotate relative to the stator by means of a rotor bearing. The rotor engages axially in a planetary gear. The rotor bearing is located within an oil path to ensure adequate lubrication of the rotor bearing. For this purpose, the rotor bearing is arranged radially within a conical ring segment-like section of an oil baffle.

[0005] The object of the present invention is to provide a solution by means of which a safe oiling of a rotor bearing of the electric traction machine can be ensured with a particularly reliable cooling of an active part of an electric traction machine.

[0006] This object is achieved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the subclaims, the description, and the figures. Features, advantages, and possible embodiments presented in the description for one of the subject matter of the independent claims are to be regarded at least analogously as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

[0007] The invention relates to an electric traction machine for a motor vehicle, in particular a motor vehicle, in particular a passenger car. The electric traction machine is designed to drive the motor vehicle using electrical energy from a traction battery. The electric traction machine comprises a stator, a rotor rotatable about an axis of rotation relative to the stator, and a hollow rotor shaft. The rotor is mounted on this hollow rotor shaft in a rotationally fixed manner. This means that the rotor can be rotated about the axis of rotation together with the rotor shaft. The axis of rotation coincides with a central axis of the hollow rotor shaft and with a central axis of the rotor. Oil can be conducted within the rotor shaft. The oil is a cooling fluid by means of which heat can be transported away from the rotor shaft, thereby cooling the rotor shaft.The rotor, which is fixed to the rotor shaft, can be cooled via the rotor shaft. The hollow space in the rotor shaft thus provides a coolant channel through which oil can flow to cool the rotor shaft.

[0008] The electric traction machine further comprises a housing enclosing the stator and the rotor. The rotor shaft is mounted on the housing by means of at least one rotor shaft bearing. In particular, the rotor shaft is mounted on the housing at its axially opposite ends via a respective rotor shaft bearing. For lubricating the at least one rotor shaft bearing, at least one outlet opening is provided in the rotor shaft, associated with this rotor shaft bearing. Oil can escape from the rotor shaft through this outlet opening. In particular, the oil escapes from the rotor shaft via the outlet opening during operation of the electric traction machine. The electric traction machine further comprises a deflection element, by means of which the oil escaped from the rotor shaft can be deflected to the rotor shaft bearing.In particular, the oil flows out of the outlet opening due to the rotation of the rotor shaft around the axis of rotation in the radial direction out of the rotor shaft. To ensure that the oil escaping from the rotor shaft is reliably guided to the rotor shaft bearing, a deflection element is provided, the oil being deflected on its outer surface upon impact, whereby the oil flows towards the rotor shaft bearing. In particular, the rotor shaft bearing is arranged in the axial direction in front of or behind the associated outlet opening. In particular, if there is no provision for oil to be sprayed into a volume enclosed by the housing, in which the stator and rotor are arranged, in such a way that this oil forms an oil mist, the rotor shaft bearings may not be sufficiently oiled.The at least one outlet opening of the hollow rotor shaft and the deflection element, through which the oil escaping from the rotor shaft is directed to the rotor shaft bearing, ensure that the rotor shaft bearing is sufficiently lubricated. This allows the rotor and rotor shaft to rotate with particularly low friction relative to the stator, allowing the electric traction machine to operate particularly efficiently.

[0009] In one possible development of the invention, it is provided that the deflecting element is part of the rotor, part of the housing, or part of the rotor shaft. This means that the deflecting element protrudes from a housing wall, or from a rotor base, or from an outer side of the rotor shaft. If the deflecting element is part of the housing, there is a relative movement of the stationary deflecting element to the outlet opening, which rotates together with the rotor shaft and through which the oil exits. This allows the oil exiting the outlet opening to be atomized particularly finely upon impact with the deflecting element, whereby the rotor shaft bearing can be lubricated particularly evenly by means of the resulting oil mist.If the deflection element is part of the rotor or the rotor shaft, then there is no relative movement between the deflection element and the outlet opening when the rotor shaft rotates around its axis of rotation, since the deflection element is indirectly held non-rotatably on the rotor shaft via the rotor base body or is part of the rotor shaft itself. As a result, the point of impact of the oil exiting the outlet opening on the deflection element is always the same. Consequently, a fixed arrangement of the deflection element relative to the outlet opening allows for precise control of how the oil exiting the rotor shaft via the outlet opening is deflected to the rotor shaft bearing.

[0010] In a further possible embodiment of the invention, it is provided that the outlet opening is provided by a radial bore in the rotor shaft and the deflection element covers the outlet opening radially outwards at least in part. The radial bore of the rotor shaft is to be understood as meaning that the radial bore extends with its longitudinal extension and thus with its central axis at least substantially in the radial direction of the rotor shaft. As a result, the oil flowing through the bore flows at least partially, in particular substantially, in the radial direction and consequently flows at least partially in the radial direction out of the outlet opening of the rotor shaft. This flow of oil in the radial direction is amplified by centrifugal forces exerted on the oil flowing in the rotor shaft due to the rotation of the rotor shaft.Because the deflection element covers the outlet opening radially outward, at least in part, the oil flowing radially outward from the rotor shaft through the outlet opening impinges on the deflection element, which in turn allows the oil to be deflected by the deflection element. The deflection direction in which the oil is deflected by the deflection element is determined by the geometry of the deflection element.

[0011] In a further possible embodiment of the invention, it is provided that a lance is arranged in the cavity of the rotor shaft and is fixed in rotation with the rotor shaft. The lance is designed to guide the oil inside the rotor shaft close to the axis of rotation and thus inside, and to return it along an inner wall of the rotor shaft that bounds the cavity. The lance is thus designed to redirect the oil flowing inside the rotor shaft. The oil flows inside the lance and thus in a first flow direction, flows out of the lance at the end of the lance and is thereby redirected around the end of the lance, whereby the oil flows back along an outer wall of the lance in a second flow direction opposite to the first flow direction. While the oil flows back along the outside of the lance, the oil flows along the inner wall of the rotor shaft, whereby the oil absorbs heat from the rotor shaft.The oil thus flows through the axial length of the rotor shaft, over which the lance extends, twice: once outward and once back again. The oil thus travels a particularly long distance within the rotor shaft, allowing the oil to absorb a particularly large amount of heat as it flows through the rotor shaft.

[0012] In a further possible embodiment of the invention, the rotor shaft has two outlet openings, wherein the outlet openings are arranged on opposite sides of the rotor in the axial direction, each further outwards than the rotor. In this case, the respective outlet openings are arranged, in particular, further inwards in the axial direction than the rotor shaft bearings assigned to the respective ends of the rotor shaft. This means that, with regard to the axial direction, the two rotor shaft bearings are arranged on the very outside, in the axial direction the two outlet openings are arranged between the two rotor shaft bearings, and in the axial direction the rotor or at least the rotor base body of the rotor is arranged between the two outlet openings. In this case, an overlap of the outlet openings, the deflection elements and the rotor or the rotor base body can be partially or completely omitted.Because the rotor shaft bearings are arranged particularly far outwards in the axial direction, the rotor shaft can be particularly well stabilized by the rotor shaft bearings. Because the outlet openings are arranged further outwards in the axial direction than the rotor or the rotor base body, the oil can be guided to the respective associated rotor shaft bearing after emerging from the respective outlet opening, bypassing the rotor if the housing or the rotor shaft has the deflection element, or at least bypassing the rotor base body if the rotor has the deflection element. This ensures that a particularly large proportion of the oil flowing out of the rotor shaft via the respective outlet opening, which is deflected by means of the associated deflection element, reaches the rotor shaft bearing to be lubricated.

[0013] In a further possible embodiment of the invention, the deflecting element is designed to atomize the oil impinging on it. For example, the deflecting element can have a structure on an impact surface where the oil emerging from the outlet impinges on the deflecting element. This structure can swirl the impinging oil and consequently atomize it. By atomizing the oil by means of the deflecting element, an oil mist can be generated, which can be used to lubricate the associated rotor shaft bearing particularly evenly.

[0014] In a further possible embodiment of the invention, it is provided that a stator winding overhang of the stator is enclosed and sealed by means of an encapsulation. Because the stator winding overhang of the stator is enclosed and sealed by means of the encapsulation, a cooling liquid, in particular oil, can be conducted within the volume enclosed by the encapsulation together with the stator. A winding of the stator can be directly cooled by means of this oil. This means that for this direct cooling, the oil flows directly along the stator winding of the stator, whereby a particularly large amount of heat can be absorbed by the stator winding by means of the cooling liquid. As a result of this particularly good cooling of the stator winding, the electric traction machine can be operated efficiently; in particular, a particularly high peak power and / or a particularly high continuous power of the electric traction machine can be achieved.Due to the encapsulation of at least one stator winding overhang, the areas within which oil is conveyed in the volume enclosed by the housing are very limited. Without the outlet openings provided in the rotor shaft and the deflection elements associated with the respective outlet openings, sufficient lubrication of the rotor shaft bearings cannot necessarily be guaranteed. The described electric traction machine with the outlet opening and the deflection element for the at least one rotor shaft bearing enables particularly reliable and sufficient lubrication of the rotor shaft bearing. Due to the direct cooling of the stator winding implemented as a result of the encapsulation of the stator winding overhang, the electric traction machine can be operated particularly efficiently.

[0015] In a further possible embodiment of the invention, it is provided that the at least one outlet opening is dimensioned with regard to its cross-section such that only a portion of the oil flowing in the rotor shaft exits the rotor shaft via this outlet opening. In particular, the outlet opening is dimensioned with regard to the size of its cross-section such that the volume flow of oil exiting the rotor shaft via this outlet opening is as small as possible and, at the same time, sufficient lubrication of the associated rotor shaft bearing can be achieved after deflection by means of the deflection element. As a result, a particularly large amount of the oil flowing within the rotor shaft can be used to cool the rotor shaft, since only the amount of oil required for lubricating the rotor shaft bearing flows out via the outlet opening associated with this rotor shaft bearing.This means that very little oil is required to operate the electric traction motor.

[0016] In a further possible embodiment of the invention, the rotor shaft bearing is designed as a rolling bearing. Rolling bearings are bearings in which bodies rolling between an inner ring and an outer ring reduce frictional resistance. They serve to fix axles and shafts and, depending on their design, absorb radial and / or axial forces while simultaneously enabling the rotation of the shaft or components mounted on the shaft, in this case the rotor. The rotor shaft bearing designed as a rolling bearing thus enables particularly stable mounting of the rotor shaft on the housing and, moreover, rotation of the rotor shaft relative to the housing about the axis of rotation with particularly low friction losses.

[0017] The invention further relates to a motor vehicle having an electric traction machine as already described in connection with the electric traction machine according to the invention. The electric traction machine is configured to drive the motor vehicle using electrical energy.

[0018] Further features of the invention may emerge from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures alone, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0019] The drawing shows:

[0020] Fig. 1 is a schematic partial section of an electric traction machine in a first embodiment; and

[0021] Fig. 2 shows a schematic partial section of the electric traction machine in a second, alternative embodiment. In the figures, identical and functionally identical elements are provided with the same reference numerals.

[0022] Figures 1 and 2 each show a sectioned view of an electric traction machine 10. In Figures 1 and 2, the electric traction machine 10 is shown in different embodiments. The following section first explains the similarities between the different embodiments of the electric traction machine 10. The electric traction machine 10 comprises a housing 12, which encloses a housing volume 14. A stator 16 and a rotor 18 are accommodated in this housing volume 14. The rotor 18 is seated in a rotationally fixed manner on a hollow rotor shaft 20. The rotor shaft 20, together with the rotor 18, is rotatable about an axis of rotation 22 during operation of the electric traction machine 10. In order to enable the rotor shaft 20 to rotate about the axis of rotation 22, the rotor shaft 20 is mounted on the housing 12 by means of two rotor shaft bearings 24. The rotor shaft bearings 24 are designed as respective rolling bearings.

[0023] The rotor shaft 20 has a cavity 26 through which oil 28 can flow as a cooling fluid. The flow path of the oil 28 in the rotor shaft 20 is indicated by respective arrows, whereby for reasons of clarity only some of the arrows are provided with the corresponding reference symbol for the oil 28. In order to be able to guide the oil 28 within the cavity 26 of the rotor shaft 20 with respect to an axial direction A of the rotor shaft 20 not only in one flow direction but in two mutually opposite flow directions, a lance 30 is arranged in the cavity 26. The lance 30 is arranged in a rotationally fixed manner within the cavity 26 of the rotor shaft 20. This means that the lance 30 rotates together with the rotor shaft 20 about the axis of rotation 22 during operation.In the present case, the lance 30 is tubular, with the oil 28 being guided within the lance 30 in a first flow direction running in the axial direction A, flowing out of the lance 30 at one end 32, being deflected around the end 32 of the lance 30, and being returned outside the lance 30 in a second flow direction opposite to the first flow direction. As the oil 28 flows back along the outer side of the lance 30, which is arranged radially outward with respect to the radial direction R, the oil 28 flows along an inner wall 34 of the rotor shaft 20 delimiting the cavity 26. As a result, the rotor shaft 20 is cooled from the inside by means of the oil 28. By being deflected by means of the lance 30, the oil 28 thus travels a particularly long flow path within the rotor shaft 20, whereby a particularly large amount of heat can be absorbed by the oil 28 from the rotor shaft 20 as it flows through the rotor shaft 20.During operation of the electric traction machine 10, the oil 28 can be introduced into the interior of the lance 30 by means of a pressure oil injection.

[0024] The axial direction A coincides with a longitudinal direction of the rotation axis 22. The radial direction R is perpendicular to the rotation axis 22.

[0025] In the present case, it is provided that respective stator winding overhangs 36 of the stator 16 are enclosed by an encapsulation and thereby sealed. This allows direct cooling of a stator winding 40 within the stator 16 by oil 28 flowing around the stator winding 40. Because the stator winding overhangs 36 are enclosed by the respective encapsulations 38, very little or no oil 28 escapes from the stator 16 via these stator winding overhangs 36, by means of which the rotor shaft bearings 24 could be lubricated. In order to nevertheless enable sufficient lubrication of the rotor shaft bearings 24, it is provided that the rotor shaft 20 has at least one outlet opening 42 for each rotor shaft bearing 24. These outlet openings 42 are provided in particular by bores in the wall of the rotor shaft 20 that run at least partially in the radial direction R.When the rotor shaft 20 rotates about the rotational axis 22, oil 28 exits the rotor shaft 20 at least partially in the radial direction R via the respective outlet openings 42.

[0026] It is now further provided that the electric traction machine 10 has at least one deflection element 44 for each rotor shaft bearing 24. The respective deflection element 44 is configured to deflect oil 28 flowing out of the rotor shaft 20 via the outlet openings 42 upon impact with the deflection element 44, whereby the oil 28 is deflected toward the associated rotor shaft bearing 24. As a result, this rotor shaft bearing 24 can be lubricated by means of the deflected oil 28. In particular, the deflection element 44 is arranged to cover the outlet opening 42 outwardly in the radial direction R, at least in regions with respect to the axis of rotation 22. This ensures that the oil 28 flowing out of the rotor shaft 20 via the respective outlet opening 42 is largely, in particular completely, deflected by means of the deflection element 44 to the associated rotor shaft bearing 24.In particular, the deflection element 44 can be configured to atomize the impinging oil 28, whereby the associated rotor shaft bearing 24 can be lubricated by means of the resulting oil mist. As can be seen in Figures 1 and 2, it is particularly provided that the outlet openings 42 are arranged further outward with respect to the axial direction A than the rotor 18, in order to prevent oil 28 escaping from the rotor shaft 20 via the respective outlet opening 42 from impinging on a rotor base body 46 of the rotor 18 instead of on the respective associated deflection element 44.

[0027] In particular, a cross-sectional area of ​​the respective outlet openings 42 is selected such that only a part of the oil 28 flowing in the rotor shaft 20 exits the rotor shaft 20 via the respective outlet openings 42. This ensures, on the one hand, that oil 28 can escape from the rotor shaft 20 via all outlet openings 42 and that sufficient oil 28 for cooling the rotor shaft 20 flows along the inner wall 34 of the rotor shaft 20, even downstream of all outlet openings 42 of the rotor shaft 20. In the embodiment shown in Fig. 1, the deflection elements 44 are part of the housing 12. In the embodiment shown in Fig. 2, one of the deflection elements 44 is part of the rotor 18. In this case, one of the deflection elements 44 protrudes from the rotor base body 46 of the rotor 18, in particular in the axial direction A. In the second embodiment of the invention shown in Fig. 2, it is provided that the other of the deflection elements 44 is part of the rotor shaft 20.So that can.

[0028] Deflection element 44 may be part of the housing 12 or part of the rotor 18 or the rotor shaft 20. In particular, all deflection elements 44 of the electric traction machine 10 may each be part of the same component or each be part of different components.

[0029] The described electric traction machine 10 enables efficient cooling of the stator winding overhangs 36 and the remaining stator winding 40 through direct slot cooling with oil 28. In this case, the stator winding overhangs 36 are encapsulated to seal off any oil flow within the slot. This means that, compared to conventional winding overhang cooling using splash oil from the stator area and bores in the rotor shaft 20 for internal or centrifugal winding overhang cooling, no oil 28 would be present in the rotor bearing area. If oil-lubricated rolling bearings were used, this could lead to a mechanical defect due to the lack of lubrication or cooling by oil on the rolling elements.

[0030] For this reason, the rotor configuration described below is provided. The lance 30 is provided within the rotor shaft 20 and rotates around the rotational axis 22 together with the rotor shaft 20 during operation. Pressure oil is injected into the cavity 26 of the rotor shaft 20, for example, on the A side. The oil 28 is conveyed inside the lance from the A side to the B side of the rotor shaft 20. On the B side, the flow of the oil 28 is geometrically deflected by 180° and flows between the outside of the lance and the inside contour of the rotor shaft back to the A side, thereby providing a major part of the rotor shaft cooling effect. The oil is drained off on the A side.In order to meet the lubrication and cooling requirements of the rolling bearings of the rotor shaft 20, bores, which can also be referred to as bearing supply bores, are provided on the A-side and B-side of the rotor shaft 20, respectively, for oil to escape from the rotor shaft 20. These bearing supply bores provide the respective outlet openings 42. The respective bearing supply bores are dimensioned such that the amount of oil escaping from the rotor shaft 20 under an existing centrifugal force is sufficient to lubricate and cool the rolling bearings. The flow of the oil 28 after exiting the bearing supply bores is transported in a targeted manner via the deflection elements 44 to the respective rolling elements of the rolling bearings. In this case, an atomization effect of the oil 28 can occur when a free jet coming from the rotor shaft 20 strikes the deflection elements 44.This atomization, or rather the oil mist directed to the rolling bearing, enables efficient wetting of the rolling bearing with the oil 28, thereby achieving good lubrication and cooling of the rolling bearing. However, the amount of oil required by the rolling bearings represents only a fraction of the total amount of oil injected into the rotor shaft 20, allowing the majority to be used to cool the rotor shaft 20. This ensures that the rotor shaft 20 is sufficiently cooled by the oil 28.

[0031] Overall, the invention shows how a rotor bearing lubrication concept of an oil-cooled electric traction machine 10 with direct slot cooling and winding head encapsulation can be implemented.

[0032] 10 electric traction machine

[0033] 12 housings

[0034] 14 housing volume

[0035] 16 Stator

[0036] 18 Rotor

[0037] 20 Rotor shaft

[0038] 22 axis of rotation

[0039] 24 rotor shaft bearings

[0040] 26 cavity

[0041] 28 Oil

[0042] 30 lance

[0043] 32 End

[0044] 34 Interior wall

[0045] 36 Stator winding head

[0046] 38 Encapsulation

[0047] 40 stator winding

[0048] 42 Exit opening

[0049] 44 Deflection element

[0050] 46 Rotor base body

[0051] A axial direction

[0052] R radial direction

Claims

Patent claims 1. An electric traction machine (10) for a motor vehicle, comprising a stator (16), a rotor (18) rotatable relative to the stator (16) about a rotational axis (22), a hollow rotor shaft (20) on which the rotor (18) is seated in a rotationally fixed manner and within which oil (28) can be guided, and a housing (12) enclosing the stator (16) and the rotor (18), wherein the rotor shaft (20) is mounted on the housing (12) by means of at least one rotor shaft bearing (24), and wherein, for lubricating the rotor shaft bearing (24), an outlet opening (42) associated with the rotor shaft bearing (24) is provided in the rotor shaft (20), through which outlet opening oil (28) can escape from the rotor shaft (20), wherein a deflection element (44) is provided, by means of which the oil (28) escaped from the rotor shaft (20) is deflected to the rotor shaft bearing (24). can be.

2. Electric traction machine (10) according to claim 1, characterized in that the deflection element (44) is part of the rotor (18) or part of the housing (12) or part of the rotor shaft (20).

3. Electric traction machine (10) according to claim 1 or 2, characterized in that the outlet opening (42) is provided by a radial bore of the rotor shaft (20) and the deflection element (44) covers the outlet opening (42) at least partially radially outwards.

4. Electric traction machine (10) according to one of the preceding claims, characterized in that a lance (30) which is fixed in rotation with the rotor shaft (20) is arranged in the cavity (26) of the rotor shaft (20), which lance is designed to return oil (28) within the rotor shaft (20) close to the axis of rotation and along an inner wall (34) of the rotor shaft (20) delimiting the cavity (26).

5. Electric traction machine (10) according to one of the preceding claims, characterized in that the rotor shaft (20) has two outlet openings (42), wherein the outlet openings (42) are arranged on opposite sides of the rotor (18) in the axial direction (A) each further outward than the rotor (18).

6. Electric traction machine (10) according to one of the preceding claims, characterized in that the deflection element (44) is designed to atomize the oil (28) impinging on this deflection element (44).

7. Electric traction machine (10) according to one of the preceding claims, characterized in that a stator winding head (36) of the stator (16) is enclosed and sealed by means of an encapsulation (38).

8. Electric traction machine (10) according to one of the preceding claims, characterized in that the outlet opening (42) is dimensioned with regard to its cross-section such that only a part of the oil (28) flowing in the rotor shaft (20) exits the rotor shaft (20) via this outlet opening (42).

9. Electric traction machine (10) according to one of the preceding claims, characterized in that the rotor shaft bearing (24) is designed as a rolling bearing.

10. Motor vehicle with an electric traction machine (10) according to one of the preceding claims.

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