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 housing (20) and a stator (12) which together delimit at least one cooling duct (22) through which a cooling fluid can flow, as a result of which the stator (12) can be cooled by means of the cooling fluid in the course of jacket cooling, the stator (12) being held on the housing (20) by means of a plurality of screw connections and having a plurality of radially protruding tabs (24) which each have an axial screw opening (26) through each of which a screw element which is held on the housing (20) for establishing the respective screw connection is axially inserted, a plurality of the tabs (24) bearing radially against the inside of the housing (20), as a result of which the stator (12) is radially centred in the housing (20) by means of the tabs (24).

Description

[0001] Electric traction machine for a motor vehicle as well as motor vehicle

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

[0003] WO 2020 / 239548 A1 discloses an electric drive in a housing with at least one electric machine comprising a stator and a rotor. The housing may be provided with a cooling water connection through which water can be supplied as a cooling medium. For this purpose, a jacket cooling system may be provided, comprising cooling channels running around a jacket section on the stator, which can be supplied with cooling water.

[0004] Furthermore, a drive arrangement with a dynamoelectric machine comprising a stator and a rotor rotatable about an axis is known from DE 102013226 804 B4. The dynamoelectric machine has a cooling jacket.

[0005] The object of the present invention is to provide a solution by which a stator of an electric machine can be cooled by means of jacket cooling and can be placed in the housing in a particularly simple and safe manner.

[0006] This problem is solved according to the invention by the objects of the independent

[0007] Claims resolved. Further possible embodiments of the invention are described in the

[0008] The dependent claims, the description, and the figures disclose the features, advantages, and possible embodiments set forth in the description for one of the subject-matter claims are to be regarded, at least analogously, as features, advantages, and possible embodiments of the respective subject-matter claims of the other independent claims and of any possible combination of the subject-matter claims, possibly in conjunction with one or more of the dependent claims.

[0009] The invention relates to an electric traction machine for a motor vehicle, in particular a car, especially a passenger car. The electric traction machine is designed to propel the motor vehicle by means of electrical energy, in particular by means of electrical energy from a vehicle battery of the motor vehicle. The electric traction machine can also be referred to as an electric motor. The electric traction machine comprises a housing and a stator. Furthermore, the electric traction machine can comprise a rotor, which can be rotated relative to the stator about an axis of rotation during operation. The housing defines a receiving space in which the rotor and the stator are to be received. Thus, the housing is designed to enclose the stator and the rotor.The housing and the stator together define at least one cooling channel through which a cooling fluid flows, enabling the stator to be cooled by means of the cooling fluid via jacket cooling. The cooling fluid is, in particular, a coolant, especially oil or water. This at least one cooling channel runs along a surface of the stator, thus enabling jacket cooling of the stator by means of the cooling fluid flowing through the at least one cooling channel.

[0010] In the electric traction machine, the stator is held to the housing by several screw connections. For this purpose, the stator has several radially projecting lugs. Each of these lugs has an axial screw opening. In other words, the screw connection runs axially through the respective lugs. The axial direction is parallel to the longitudinal axis of the rotor's axis of rotation, around which the rotor rotates relative to the stator during operation. The radial direction is perpendicular to the axial direction. A screw element is inserted axially through each screw opening, which is held against the housing to create the respective screw connection.This means that the respective screw elements are inserted through the corresponding axial screw openings in the lugs and screwed to the housing, in particular by the engagement of a thread of the screw element with a thread of the housing. In the electric traction machine, it is further provided that several of the lugs bear radially against the inside of the housing, thereby radially centering the stator within the housing via the lugs. This means that at least two of the stator lugs, with their radially outermost outer surface, bear against an inner surface of the housing. Because the multiple lugs bear against the housing in a radial direction, the stator is radially supported against the inside of the housing. Thus, the stator is radially centered within the housing via the lugs.The tabs thus enable, firstly, the precise radial centering of the stator in the housing and, secondly, allow the stator to be positioned without contact with the housing in areas different from the tabs. This maintains a gap between the stator and the housing, through which the cooling fluid can flow. This allows for reliable, large-area jacket cooling of the stator by means of the cooling fluid flowing between the stator and the housing.

[0011] In a possible embodiment of the invention, at least one of the tabs is supported circumferentially against the housing. This means that at least one of the tabs bears against the inside of the housing in the circumferential direction. For this purpose, the inside of the housing can have a contact surface that extends at least partially in a radial direction, allowing the tab to be pressed against this area of ​​the inner wall of the housing in the circumferential direction. By supporting the tab circumferentially against the housing, rotational movement of the stator about the rotor's axis of rotation along the circumferential direction in the direction in which the tab is supported against the housing can be prevented. This significantly reduces the risk of the stator twisting relative to the housing, and consequently, the stator is positioned particularly securely within the housing.

[0012] In this context, it can be provided that at least one of the tabs is supported radially outwards against the housing and against the housing on opposite sides in the circumferential direction, thereby preventing the stator from rotating against the housing in the circumferential direction via this tab. Because the stator is supported against the housing on opposite sides in the circumferential direction via this tab, rotational movement of the stator relative to the housing along the circumferential direction can be particularly effectively prevented. The stator is thus securely centered and positioned in the housing both radially and circumferentially via the at least one tab. Consequently, torques introduced into the stator during operation via this at least one tab can be particularly effectively transferred into the housing via the support provided by the housing.

[0013] In a further possible embodiment of the invention, the multiple tabs are arranged to bear radially against the inside of the housing along their entire axial length. This creates line contact between each tab and the housing. In particular, the tabs extend along the entire axial length of a stator base body, or more specifically, the entire stator. This ensures that the stator is precisely radially centered and positioned along the entire axial length of the tabs, the stator base body, or the entire stator by means of the radial support provided by the tabs on the housing.The line contact of the tabs with the housing enables a particularly secure radial centering of the stator relative to the housing over a particularly long axial length range of the stator.

[0014] In a further possible embodiment of the invention, the respective tabs have a triangular cross-section perpendicular to the axial direction. The corners of the tabs can be rounded in cross-section. The inner wall of the housing, particularly in the area where each tab is to be radially positioned, can have a circular arc shape in cross-section. Thus, when the tab is inserted into the sector-shaped indentation of the housing, the tab only contacts the inner wall of the housing at the tips of its triangular cross-section. This allows for a particularly small contact area between the tabs and the inner wall of the housing, ensuring reliable centering of the stator within the housing, both radially and, optionally, circumferentially.Due to the exceptionally small contact area between the stator, particularly the lugs, and the housing, a particularly large area of ​​the stator's outer surface can remain free from direct contact with the housing and thus be exposed to the cooling fluid. This allows for particularly efficient stator cooling, especially in the case of jacket cooling. The triangular cross-sectional shape of the lugs enables both radial support of the lugs against the housing and circumferential support against the housing on opposite sides.

[0015] In another possible embodiment of the invention, the respective screw elements are designed as tie rods. The stator can be securely fastened to the housing by means of these tie rods. The tie rods ensure a tensile-resistant connection between the stator and the housing.

[0016] In a further possible embodiment of the invention, the stator comprises at least three tabs, each of which bears radially against the inside of the housing. The use of at least three tabs, and in particular the use of exactly three tabs, enables precise radial centering and thus alignment of the stator relative to the housing. The fewer tabs provided for centering, the lighter the stator, and consequently the electric traction machine, can be designed. Therefore, providing the stator with exactly three tabs enables, on the one hand, particularly precise centering of the stator within the housing and, on the other hand, a particularly lightweight design of the stator.

[0017] In a further possible embodiment of the invention, the tabs by which the stator is radially supported on the inside of the housing are arranged on the outside of the stator, distributed evenly around its circumference. In this configuration, the tabs can, in particular, project from the stator in a radial pattern. Because the tabs are arranged at least substantially evenly around the circumference of the stator, the stator can be positioned with exceptional precision and reliability within the housing using a particularly small number of tabs.

[0018] In a further possible embodiment of the invention, the stator is manufactured as a laminated core consisting of a plurality of stator laminations stacked axially. In particular, the axially stacked stator laminations are firmly connected to one another. By constructing the stator from a laminated core, the electric traction machine can be provided with particularly high performance and energy efficiency. To manufacture the laminated core, the stacked stator laminations are bonded together or connected by another packing process. By constructing the stator as a laminated core, the magnetic fields generated within the stator can be amplified. Furthermore, the individual stator tabs can be provided particularly easily by punching out tabs from the individual stator laminations.When manufacturing the stator core, the respective tabs of the axially stacked stator laminations are designed to overlap axially, and in particular to completely overlap each other axially. Especially when manufacturing the stator core from the multitude of stacked stator laminations, the stator can be produced particularly easily with these multiple tabs.

[0019] The invention further relates to a motor vehicle with an electric traction machine as already described in connection with the electric traction machine according to the invention. Additionally, the motor vehicle can include a vehicle battery, in particular a traction battery, which is configured to provide electrical energy for the electric traction machine. In other words, the electric traction machine can be driven by means of electrical energy from the traction battery.

[0020] Further features of the invention may become apparent 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 themselves, can be used not only in the combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0021] The drawing shows in Fig. 1 a schematic sectional view of a stator and a housing of an electric traction machine for a motor vehicle;

[0022] Fig. 2 shows a schematic perspective view of the stator; and

[0023] Fig. 3 shows a schematic side view of the electric traction machine with the

[0024] Stator, housing, rotor and rotor shaft.

[0025] In the figures, identical and functionally equivalent elements are provided with the same reference symbols.

[0026] Figure 3 shows a schematic side view of an electric traction machine 10 for a motor vehicle. The electric traction machine 10 is designed to electrically power the motor vehicle using electrical energy. In this case, the electric traction machine 10 comprises a stator 12, a rotor 16 which is rotatable about an axis of rotation 14 relative to the stator 12 during operation, and a rotor shaft 18 on which the rotor 16 is fixedly mounted and which, together with the rotor 16, is rotated about the axis of rotation 14 during operation. Furthermore, the electric traction machine 10 comprises a housing 20 which radially encloses the rotor shaft 18, the rotor 16, and the stator 12, at least in a longitudinal section extending in the axial direction A. The axial direction A runs parallel to the longitudinal direction of the axis of rotation 14. The radial direction R is perpendicular to the axial direction A.The stator 12 is designed as a laminated core with a plurality of stator laminations stacked on top of each other in the axial direction A. The stator 12 is shown in a schematic perspective view in Fig. 2. In Fig. 1, the stator 12 arranged in the housing 20 is shown in section, with the section plane perpendicular to the axial direction A. In Figures 1 and 3, the axial direction A extends into the plane of the image.

[0027] It is provided that the stator 12 and the housing 20 together define at least one cooling channel 22 through which a cooling fluid flows. By guiding cooling fluid through the cooling channel 22, the stator 12 can be cooled by jacket cooling. Furthermore, it is provided that the stator 12 is, or will be, attached to the housing 20 by several screw connections. The stator 12 comprises several tabs 24, in this case exactly four tabs 24, which project radially R from the stator 12. As can be seen particularly well in Fig. 2, it is provided that the respective tabs 24 extend axially A over the entire axial length A of the laminated core. As can be seen particularly well in Figures 1 and 3, it is provided that the tabs 24 are arranged on the outside of the stator 12, evenly distributed around its circumference.This means that the tabs 24 are equidistant from each other tab 24 immediately adjacent to them in the circumferential direction U. As can be seen particularly well in Figures 1 and 3, each tab 24 has a screw opening 26 extending axially A, through which a screw element can be inserted axially. By means of the screw elements inserted axially A through the respective screw openings 26, screw connections can be made to the housing 20, thereby holding the stator 12 to the housing 20 via these screw connections. In this design, the respective screw elements are configured as tie rods. The stator 12 is designed to bear against the housing 20 only in the area of ​​the tabs 24 on its circumferential outer surface U, specifically against an inner wall 28 of the housing 20.

[0028] Figure 1 shows an enlarged section in which one of the tabs 24 rests against the inner wall 28 of the housing 20. It can be seen that the tab 24, in its cross-section perpendicular to the axial direction A, has at least a substantially triangular shape, with each corner of the triangular shape being rounded. This allows for reliable support of the stator 12 against the housing 20 via the tab 24, even with particularly small contact areas between the tab 24 and the housing 20. In this case, one of the points of the triangular shape of the tab 24 is supported radially R against the inner wall 28 of the housing 20. The other two points of the triangular shape of the tab 24 are supported along the circumferential direction U on opposite sides of the inner wall 28 of the housing 20.By attaching the tab 24 to the inner wall 28 of the housing 20 on opposite sides in the circumferential direction U, the stator 12 can be particularly easily secured against rotation relative to the housing 20 with respect to the axis of rotation 14. The radial attachment and thus support of the tab 24 against the inner wall 28 of the housing 20 enables particularly precise radial centering of the stator 12 to the housing 20, especially within the housing 20. It is designed that the tabs 24 bear radially against the inner wall 28 of the housing 20 along their entire length in the axial direction A, thus establishing line contact between the respective tab 24 and the housing 20, in particular its inner wall 28.In this case, it is provided that the respective tabs 24 are additionally supported along their entire length in the axial direction A against the inner wall 28 of the housing 20 on opposite sides in the circumferential direction U. This ensures particularly reliable anti-rotation of the stator 12 over the entire length of the laminated core in the axial direction A.

[0029] As can be seen particularly well in Fig. 1, the inner wall 28 of the housing 20 has a circular arc-shaped inner contour in cross-section in the area where the respective associated tab 24 is to be placed against the inner wall 28. Because the inner wall 28 has this circular arc-shaped inner contour and the associated tab 24 has a cross-sectional shape that is at least substantially triangular, the tab 24 and the inner wall 28 have a particularly small contact area with each other. This allows coolant to flow between the inner wall 28 and the respective tabs 24 in areas where the tab 24 is not in direct contact with the inner wall 28, thereby dissipating heat from the stator 12. This enables particularly efficient cooling of the stator 12.

[0030] The electric traction machine 10 can, in particular, be an oil-jacketed cooling machine. This type of cooling can be greatly improved by structuring the outer surface of the stator 12; however, it is simultaneously necessary to ensure that the stator 12 is supported, centered, and torque-resistant within the housing 20.

[0031] Typically, a stator lamination stack is centered and secured in the housing 20 via its outer surface, for example, by a cross-press fit. When using oil jacket cooling, the stator 12 is attached to the housing 20 via tie rods, since the outer surface of the stator 12 must be wetted with the coolant. Consequently, a press fit is no longer possible. The solution described in conjunction with the figures offers a way to center the stator 12, which is attached to the housing 20 via tie rods and is to be cooled by means of jacket cooling. It is possible that the stator 12 is only attached to the housing 20 via screw connections on one of its sides opposite A in the axial direction. As a result, the stator 12 can cantilever freely. Shocks, vibrations, or other operating loads can lead to impermissible deformations or displacements if the stator 12 is not adequately supported or centered.These deformations or displacements of the stator 12 can result in the stator 12 and the rotor 16 unintentionally touching each other.

[0032] In the electric traction machine 10 described in connection with the figures, the stator 12 is positively guided and anchored in the housing 20 along its entire length in the axial direction A. This guidance is achieved via the lugs 24. The lugs 24 enable radial centering, particularly through line contact with the housing 20. Additionally, torques can be transmitted from the stator 12 to the housing 20 via the tangential contact surfaces of the lugs 24. The positive locking between the stator 12 and the housing 20 ensures a high level of operational reliability. The lugs 24 can be manufactured in a sheet metal stamping process together with the sheet metal geometry of the respective stator laminations. Due to the triangular shape of the lugs 24, each can have up to three lines of contact with the housing 20.Machining the housing 20 can include creating a cylindrical bore for the stator 12 and additionally creating a further cylindrical bore of smaller diameter for each tab 24. The stator 12 is inserted into this machined area of ​​the housing 20 and axially fastened to the housing 20 by means of tie rods. It is possible for the different tabs 24 to have different designs. For example, only some of the tabs 24 may be designed to be supported radially against the housing 20. Furthermore, only some of the tabs 24 may be designed to be supported circumferentially U against the inner wall 28 of the housing 20.

[0033] Overall, the invention demonstrates how a bolted stator lamination stack, in this case the stator 12, can be centered and torque-supported within the housing 20. Reference numeral list 10 electric traction machine

[0034] 12 Stator

[0035] 14 axis of rotation

[0036] 16 Rotor

[0037] 18 Rotor shaft 20 Housing

[0038] 22 Cooling fluid

[0039] 24 tabs

[0040] 26 screw opening

[0041] 28 Inner wall A axial direction

[0042] R radial direction

[0043] U circumferential direction

Claims

Patent claims 1. Electric traction machine (10) for a motor vehicle, comprising a housing (20) and a stator (12), which together define at least one cooling channel (22) through which a cooling fluid can flow, whereby the stator (12) can be cooled by means of the cooling fluid within the framework of a jacket cooling system, wherein the stator (12) is held on the housing (20) by means of several screw connections and has several radially projecting tabs (24), each of which has an axial screw opening (26), through which a screw element is inserted axially, which is held on the housing (20) to establish the respective screw connection, wherein several of the tabs (24) bear radially inside the housing (20), whereby the stator (12) is radially centered in the housing (20) via the tabs (24).

2. Electric traction machine (10) according to claim 1 , characterized in that at least one of the tabs (24) is supported in the circumferential direction (U) against the housing (20).

3. Electric traction machine (10) according to claim 2, characterized in that at least one of the tabs (24) is supported radially outwards on the housing (20) and is supported against the housing (20) on sides opposite each other in the circumferential direction (U), whereby the stator (12) is secured against rotation in the circumferential direction (U) against the housing (20) via this tab (24).

4. Electric traction machine (10) according to one of the preceding claims, characterized in that the several tabs (24) bear radially inside the housing (20) over their entire length extending in the axial direction (A), thereby creating line contact between the respective tab (24) and the housing (20).

5. Electric traction machine (10) according to one of the preceding claims, characterized in that the respective tabs (24) have a triangular basic shape in their cross-section extending perpendicular to the axial direction (A).

6. Electric traction machine (10) according to one of the preceding claims, characterized in that the respective screw elements are designed as respective tie rods.

7. Electric traction machine (10) according to one of the preceding claims, characterized in that the stator (12) comprises at least three tabs (24) which each bear radially inside the housing (20).

8. Electric traction machine (10) according to one of the preceding claims, characterized in that the tabs (24) by which the stator (12) is radially supported on the inside of the housing (20) are arranged on the outside of the stator (12) distributed evenly over a circumference of the stator (12).

9. Electric traction machine (10) according to one of the preceding claims, characterized in that the stator (12) is manufactured as a laminated core from a plurality of stator laminations stacked on top of each other in the axial direction (A).

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

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