Conical gap seal in an electromechanical axle drive train

Abstract

A device (1) is proposed which has a sealing arrangement with a standing cone (3) and a rotating cone (2), wherein the standing cone (3) is connected to a housing (4) in a rotationally fixed manner and the rotating cone (2) is connected to a rotating shaft (5) in a rotationally fixed manner, wherein the standing cone (3) and the rotating cone (2) are nested without contact with their cone surfaces (6, 7) so that a gap (8) is formed between the cone surfaces (6, 7), through which, in operation, a lubricant flow (9) is guided from the axis of rotation (10) of the shaft (5) in a radial direction to a drainage bore (11) in the housing (4).

Description

In current technology, gearboxes of electric motors, for example in an electromechanical axle drive train for a motor vehicle, are sealed from the environment using radial shaft seals. Therefore, it is also advantageous to use radial shaft seals within the electromechanical axle drive train to seal components and spaces. Labyrinth seals are preferred as a low-loss alternative, but these are more complex to manufacture and assemble, and therefore also more expensive. The invention relates to a device as a sealing arrangement in an electromechanical axle drive train with a gearbox and an electric motor, wherein the electric motor is configured with the gearbox for propelling the motor vehicle. DE 10 2023 101 220 A1 shows a labyrinth seal between an output shaft and a housing at the point where the output shaft exits the housing. US 2024 / 003 0 774 A shows a conically shaped component for directing lubricant to a drain hole in the housing. DE 10 2021 121 969 A1 discloses an electric axle drive train of a motor vehicle, comprising an electric machine with a stator and a rotor rotatable relative to the stator, which is coupled to a gear arrangement for torque transmission, wherein the electric axle drive train has at least one shaft rotatably mounted in a rolling bearing, and the rolling bearing is axially secured at least on one side relative to the shaft by means of a shaft nut that can be screwed onto the shaft, wherein the rolling bearing is arranged in a dry room and the shaft nut in a wet room of the electric drive train, wherein a first sealing ring with a first contour is arranged on the shaft nut, which forms a labyrinth seal with a corresponding second contour of a bearing seat of the rolling bearing and / or a second sealing ring arranged on the bearing seat. DE 10 2021 123 307 A1 discloses an electric axle drive train for an electrically powered motor vehicle, comprising an electric machine with a rotor rotatably mounted relative to a stator and a rotor shaft, and a transmission arrangement actuated by a hydraulic fluid, which can be coupled to the rotor of the electric machine in a torque-transmitting manner and the electric machine and the transmission arrangement form a structural unit, and the rotor shaft engages axially in a differential gear of the transmission arrangement, wherein the differential gear has a differential sun gear arranged coaxially to the rotor shaft, which is connected to a first output shaft of the electric axle drive train in a torque-transmitting manner, wherein a rotor disk is operatively connected to the rotor shaft in a torque-transmitting manner and is designed such that the rotor disk and the differential sun gear form a labyrinth seal with a sealing gap.which separates a wet chamber of the differential gear, supplied with hydraulic fluid, from a dry chamber of the electric machine, and the rotor disk is configured such that, when the rotor shaft and / or the differential sun gear rotates, a centrifugal force-induced centrifugal force is exerted on the hydraulic fluid in the sealing gap, directed towards the wet chamber. DE 10 2021 121 903 A1 discloses an electric axle drive train for an electrically powered motor vehicle, comprising an electric machine with a rotor rotatably mounted relative to a stator and a rotor shaft, and a gear arrangement actuated by a hydraulic fluid, which can be coupled to the rotor of the electric machine in a torque-transmitting manner and the electric machine and the gear arrangement form a structural unit, and the rotor shaft engages axially in the gear arrangement, wherein a rotor disk is fixed non-rotatably to the rotor shaft and a housing disk is arranged non-rotatably on a housing component of the electric axle drive train, wherein the rotor disk and the housing disk form a labyrinth seal with a sealing gap and the rotor disk is configured such thatthat when the rotor shaft rotates, the rotor disk causes a centrifugal effect on the hydraulic fluid directed axially towards the gearbox assembly. DE 33 30 473 A1 discloses a non-contact seal. This non-contact seal serves to seal between a stationary machine part and a rotating machine part, for example, a gear shaft. It consists of a first sealing element, designed as a rotating lubricant ring, and a second sealing element, fixed in the stationary part, with a receiving chamber, an outer circumferential channel, and at least one drain hole. This second sealing element has a radially oriented sealing surface positioned opposite the end face of the lubricant ring, forming an annular sealing gap with it. The lubricant ring contains a centrifugally acting disc in the form of a convex-concave lens with an annular lubrication edge and a hub attached to the shaft, which projects axially beyond the lubrication edge.Part of the stationary sealing element protrudes into the interior of the centrifugal disc and is designed as an approximately spherical segment, enclosed on the outside by the concave boundary surface. DE 85 33 308 U1 discloses a rotary seal consisting of an inner part with several sealing teeth and an outer part with a bore. The heads of the sealing teeth are arranged on a conical surface, and the bore of the outer part is also conical. The heads of the sealing teeth and the bore either directly touch or have a minimal distance between them. DE 27 20 135 A1 discloses a ready-to-install gap or labyrinth seal. This seal consists of an inner and an outer ring, the facing surfaces of which are profiled to interlock and form an approximately zigzag-shaped sealing gap. The rings can optionally rotate, and a drain opening can be provided in the non-rotating ring. The zigzag-shaped sealing gap runs axially such that its starting point on one side of the rings is a smaller radial distance from the center than its end point on the other side. The task is to improve the existing sealing in an electromechanical axle drive train. The problem is solved according to the invention by a device with a sealing arrangement consisting of a standing cone and a rotating cone, wherein the standing cone is non-rotatably connected to a housing and the rotating cone is non-rotatably connected to a rotating shaft, in that the standing cone and the rotating cone are nested without contact with their cone surfaces, so that a gap is formed between the cone surfaces, through which a lubricant flow is guided in operation from the axis of rotation of the shaft in a radial direction to a drainage bore in the housing. The solution according to the invention thus transports the lubricant, present in the form of oil, which has penetrated the sealing arrangement, back out again during operation and at standstill. During operation, the lubricant is transported in a centrifugal direction, while at standstill the lubricant runs off along the conical surfaces, advantageously providing a drainage bore from the housing so that the lubricant cannot collect within the sealing arrangement. For the purposes of the invention, a standing cone is understood to be a component which presents a conical surface for the gap opposite a conical surface of the rotating cone. The standing cone is fixedly anchored and positioned in the housing in a rotationally stable manner – it therefore does not exhibit any rotation about its axis of symmetry formed by the conical surface. For the purposes of the invention, a rotary cone is understood to be a component which presents a conical surface for the gap opposite a conical surface of the stationary cone. In contrast to the stationary cone, the rotary cone rotates about its axis of symmetry formed by the conical surface. Thus, the rotary cone can preferably be mounted on a shaft in a rotationally fixed manner and rotate with it without relative rotational speed. Thus, the rotational movements of the standing cone and the rotating cone relative to each other are to be understood as relative rotations, whereby the standing cone is fixed relative to its environment and its degree of freedom to rotate about its axis of symmetry relative to the environment remains blocked for the observer, while when looking from the standing cone to the rotating cone, the rotating cone rotates relative to the standing cone around the axis of rotation of the rotating cone. The conical surfaces of the standing cone and the rotating cone are preferably congruent to each other so that during operation a substantially geometrically constant gap is formed between the two surfaces, which is also capable in its dimensions of allowing a lubricant present as oil to pass through in different temperature ranges. Particularly at the interface between the gearbox and the electric motor, improved sealing is now achieved by the solution according to the invention, even when stationary or at low speeds. The components of the solution according to the invention are also less susceptible to temperature fluctuations. Due to the absence of direct physical contact between the stationary cone and the rotating cone, no wear occurs at this sealing point of the sealing assembly, thus preventing any abrasion from entering the lubricant. Furthermore, there is no friction within the sealing assembly that could impede the rotation of the shaft. According to the invention, the rotary cone has several ribs on its conical surface as a centrifugal geometry. The ribs can be advantageously formed in sheet metal, similar to the elevations of the wave-like geometry, by forming tabs from the lateral surface of the rotary cone or its conical surface. In one embodiment of the invention, the rotary cone is fixed to the shaft by means of a cylindrical seating surface. Advantageously, the cylindrical seating surface is adapted to the outer surface of the shaft in the area of ​​the seat and is provided with an anti-rotation feature designed as an interference fit, so that the rotary cone and shaft can rotate with each other, but not around each other. Alternatively, it is possible to provide a seating surface on the rotary cone that deviates from a cylindrical shape and thus forms an anti-rotation feature by means of a positive locking mechanism. In one embodiment of the invention, the standing cone with a cylindrical seating surface is firmly seated in a cylindrical receptacle within the housing. In contrast to variations in the seating surface geometry of the rotary cone, the cylindrical shape of the standing cone is clearly the preferred variant, since cylindrical shapes are extremely easy and cost-effective to integrate into the housing. Another embodiment of the invention provides that the rotary cone has a centrifugal geometry which is arranged directionally in the gap and facilitates the lubricant flow. The centrifugal geometry can be designed – explained in more detail below – as a surface without geometric features, a wave-like geometry consisting of depressions and protrusions, or as ribbing with multiple ribs / ridges. Functionally, the centrifugal geometry is positioned in the gap and is capable of promoting or improving the lubricant flow so that the flow is maintained during operation and is established even at low speeds in the operation of the electromechanical axle drive train. This ensures that fluid levels within the sealing assembly are rapidly reduced. In an advantageous embodiment, the standing cone has several recesses distributed around its circumference. These recesses serve to direct any lubricant present within the sealing assembly, when it is at rest, to the drainage bore of the housing, thus draining the sealing assembly and / or the standing cone free of lubricant. The recesses can be part of the conical surface of the standing cone or they can be separate components, so that the recesses are formed by the standing cone itself and the conical surfaces remain free of the recesses. Another embodiment provides that the housing has at least one axial drainage channel. Extending in the axial direction – thus parallel to the shaft's direction of travel and its axis of rotation – this axial drainage channel can also be very easily incorporated into a cast housing. The drainage channel preferably complements the housing's drainage bore in order to keep the sealing assembly and / or the cone free of lubricant, analogous to the recesses in the standing cone. In a more detailed embodiment of the invention, the rotary cone has a surface free of geometric features on its conical surface as a centrifugal geometry. In this context, "free of geometric features" describes a surface that has no additional geometries projecting from the surface and defining it, such as ribs, grooves, or similar features, visible to the naked eye. Any surface roughness is considered beneficial from a tribological and fluid dynamics perspective, with regard to the function and effectiveness of the lubricant flow through the gap caused by the relative movement of the two conical surfaces to each other, and is therefore to be included as a geometrically free surface. An alternative embodiment of the invention provides that the rotary cone has a wave-like geometry consisting of depressions and protrusions on its conical surface as a centrifugal geometry. A wave-like geometry can be particularly well implemented in a sheet metal component. The depressions and protrusions, periodically distributed around the circumference, preferably form a sinusoidal shape in cross-section, so that the ingress of air into the lubricant (used as oil) is minimized. According to one embodiment of the invention, the device further comprises a bearing that is in direct contact with the lubricant flow exiting the gap. The lubricant dispensed from the sealing arrangement thus comes into contact with the bearing in subsequent use. The bearing is preferably designed as a rolling bearing, in particular as a ball bearing. Therefore, the lubricant flow, determined by the design and installation space of the sealing arrangement, is sufficient in quantity to provide the bearing with any necessary lubrication. A seal between the bearing and the sealing arrangement can be omitted; however, it may be advantageous to provide a seal on the axial side of the bearing facing away from the sealing arrangement to prevent the lubricant penetrating the bearing from contaminating other components, such as electronic components. In an electromechanical axle drive train, the sealing arrangement separates a dry chamber from a wet chamber, with the dry chamber housing an electric motor and the wet chamber housing a gearbox. The centrifugal force acting on the lubricant in the gap empties the sealing arrangement, directing the lubricant to the drainage bore in the housing, which then carries it to a reservoir. From the reservoir, the lubricant can be returned to the points requiring lubrication within the electromechanical axle drive train. Character description Further embodiments of the invention are explained in more detail with reference to the figures. Figure 1 shows a sectional view through the device according to the invention, Figure 2 shows a detail view of the section according to Figure 1, Figure 3 shows a perspective detail view of the location of the section according to Figure 1, Figure 4 shows an embodiment of the stationary cone (standing cone), Figure 5a shows a first embodiment of the rotating cone (rotating cone), Figure 5b shows a second embodiment of the rotating cone (rotating cone), and Figure 5c shows a third embodiment of the rotating cone (rotating cone). Fig. 1 shows a sectional view through the device 1 according to the invention. It depicts a sealing arrangement consisting of a fixed cone 3 and a rotating cone 2, which are nested inside one another to seal a dry chamber from a wet chamber. The fixed cone 3 and the rotating cone 2 form a gap 8 with their opposing conical surfaces 6 and 7, meaning that the two components 2 and 3 are not in direct contact with each other. The fixed cone 3 is inserted into a receptacle 14 of the housing 4 and rests with one of its end faces against a contact surface 25 that defines the receptacle 14. The seating surface 13 of the fixed cone 3 is designed as a cylinder, and the receptacle 14 also has a cylinder that fits precisely with the seating surface 13 to ensure a secure fit. The rotary cone 2, with its cylindrical seat 12, is mounted on a shaft 5 and is secured axially to the shaft 5 by an O-ring 24 located in the seat 12. The O-ring 24 seals the axial contact between the rotary cone 2 and the shaft 5. Adjacent to the rotary cone 2, a ball bearing 21 is positioned on the shaft 5. An output shaft 22 is arranged through the shaft 5 and thus coaxially with it. Components 2, 5, 21, and 22 rotate about a common axis of rotation 10. The housing 4 has a catch geometry 23 in the area of ​​the receptacle 14, which is capable of collecting any lubricant that is to be drained and feeding it to the stationary cone 3. In this way, the chambers 29 (see description of the figure after Fig. 4) are filled with the lubricant to be drained. The illustration according to Fig.The 4 visible and described recesses 16 are in fluid-conducting connection with the drainage channel 17 arranged geodetically below the standing cone 3, which can thus supply the lubricant to the drainage bore 11 of the housing 4. Thus, no radial shaft seal is required between the output shaft 22 and the housing 4, since the lubricant is collected by the catch geometry 23 and fed to the sealing arrangement. The catch geometry 23 is also capable of collecting and discharging the lubricant during lateral accelerations while driving the motor vehicle with the electromechanical axle drive train according to the invention. The functionality of the device 1 according to the invention is enlarged and thus better illustrated by the figure in Fig. 2. Fig. 2 shows a detailed view of the section according to Fig. 1. In this illustration according to Fig. 2, a portion of the lubricant flow 9 is shown, which flows through the gap 9. The opening of the receptacle 14, formed by the trap geometry 23, captures the lubricant from the dry chamber and directs it to the standing cone 3. The lubricant flow 9 flows through a remaining gap between the standing cone 3 and the shaft 5 to the gap 8 formed by the two opposing cone surfaces 6, 7 and can flow below the axis of rotation 10 by gravity when stationary to the drainage bore 11, or, during operation, the centrifugal force exerted on the lubricant by the centrifugal geometry 15 can be directed through the gap 8. When the lubricant flow 9 exits the gap 8, the adjacent bearing 21 can be wetted by lubricant. Fig. 3 shows a perspective detail view of the location of the cut according to Fig. 1. In addition to the dynamic lubricant delivery during the relative rotation of both cone surfaces 6, 7, the lubricant flow 9 can take a supplementary path both at standstill and during operation. This path leads from the trap geometry 23 into the receptacle 14 and at least partially fills at least one of the chambers 29. Through the geodesically located recess 16 at the bottom, the lubricant flow 9 can continue its path via the drainage channel 17 formed by the housing 4 to the drainage bore 11, thus removing lubricant from the dry chamber. Fig. 4 shows an embodiment of the upright cone 3 (standing cone). The view of its conical surface 7 remains obscured by the component itself. To stabilize the standing cone 3, it has several stiffening ribs 28 distributed around its circumference, which, due to their discrete rib-like design, also separate several chambers 29 distributed around the circumference. Thus, in this embodiment, for the purposes of describing the embodiment in isolated illustrations, a pair of stiffening ribs 28 separates a chamber 29, which has a connection to the cylindrical outer circumferential surface 30 of the standing cone 3 via three recesses 16. The outer circumferential surface 30 fits precisely into the receptacle 14 of the housing 4 (see illustrations in Fig. 1, Fig. 2, Fig. 3), with the recesses 16 interrupting the contact between the standing cone 3 and the contact surface 25 of the receptacle 14 of the housing 4 in the circumferential direction.Thus, with a specific distribution of the recesses 16 around the circumference, mathematically related to the diameter of the outer circumferential surface 30, there is always a fluid-conducting overlap of the opening cross-sections of the recesses 16 with the drainage bore 11 and / or the drainage channel 17 of the housing 4. This allows the lubricant that has entered the receptacle 14 to drain away. The recesses 16, stiffening ribs 28 and chambers 29 in the illustration, which are marked with reference symbols, are shown with reference lines only as examples - it is clearly evident that recesses 16 are present multiple times around the circumference and are identical in shape to each other. Figure 5a shows a first embodiment of the rotating cone 2 (rotary cone) in a smooth design, in which the lubricant transport through the rotary cone 2 is achieved tribologically via the surface of its cylindrical conical surface 6 by utilizing adhesive forces. The lubricant that has come into contact with the surface of the rotary cone 2 is carried along by adhesion. A flow is created within the entire lubricant, which effects the movement of the lubricant. Figure 5b shows a second embodiment of the rotating cone 2 (rotary cone) in a corrugated design, in which the lubricant supply is achieved by corrugated recesses 18 and protrusions 19 incorporated into the rotary cone 2. The recesses 18 and protrusions 19 are arranged alternately around the circumference and repeat regularly. Furthermore, the shapes of the individual recesses 18 and the shapes of the individual protrusions 19 are identical. Advantageously, these shapes have been formed into the rotary cone 2 by a forming process. The recesses 18 and protrusions 19 in the figure, identified by reference numerals, are shown with reference lines as examples – it is clearly evident that the recesses 18 and protrusions 19 are present multiple times around the circumference. Fig. 5c shows a third embodiment of the rotating cone 2 (rotary cone) in a ribbed design, in which the lubricant supply is achieved by ribs 20 formed by the rotary cone 2. The ribs 20 project radially as isolated, axially oriented webs and are repeated regularly in the circumferential direction. The ribs 20 in the figure, marked with reference numerals, are shown with reference lines as examples – it is clearly evident that the ribs 20 are present multiple times around the circumference and are identical in shape to one another. The ribs 20 and the recesses 18 with the protrusions 19 enhance the conveying effect in the gap 8 when the shaft 5 rotates. Plastic or metal, preferably sheet metal, can be used as the material for the rotary cone 2 and / or the fixed cone 3 according to the aforementioned embodiments shown in the figures. The rotary cone 2 can also be formed as a single component of the shaft 5, and the fixed cone 3 can be formed as a single component of the housing 4. Reference symbol list 1 Device 2 Rotating cone 3 Stationary cone 4 Housing 5 Shaft 6 Cone surface (rotating cone) 7 Cone surface (stationary cone) 8 Gap 9 Lubricant flow 10 Axis of rotation 11 Drainage bore 12 Seat surface (rotating cone) 13 Seat surface (stationary cone) 14 Mounting (housing) 15 Centrifugal geometry 16 Recess 17 Drainage groove 18 Recess 19 Raise 20 Rib 21 Bearing 22 Output shaft 23 Catching geometry 24 O-ring 25 Contact surface (of the housing mounting) 26 Axis of symmetry (rotating cone) 27 Axis of symmetry (stationary cone) 28 Stiffening ribs 29 Chamber 30 Outer circumferential surface (stationary cone)

Claims

Device (1) with a sealing arrangement comprising a standing cone (3) and a rotating cone (2), wherein the standing cone (3) is non-rotatably connected to a housing (4) and the rotating cone (2) is non-rotatably connected to a rotating shaft (5), the standing cone (3) and the rotating cone (2) are nested without contact with their cone surfaces (6, 7) so that a gap (8) is formed between the cone surfaces (6, 7), through which, during operation, a lubricant flow (9) is guided from the axis of rotation (10) of the shaft (5) in a radial direction to a drainage bore (11) in the housing (4), characterized in that the rotating cone (2) has several ribs (20) on its cone surface (6) as a centrifugal geometry (15). Device (1) according to claim 1, characterized in that the rotary cone (2) is fixedly seated on the shaft (5) with a cylindrical seating surface (12). Device (1) according to one of the preceding claims, characterized in that the standing cone (3) with a cylindrical seating surface (13) is firmly seated in a cylindrical receptacle (14) of the housing (4) in the housing (4). Device (1) according to one of the preceding claims, characterized in that the rotary cone (2) has a centrifugal geometry (15) which is directed in the gap (8) and accomplishes the lubricant flow (9). Device (1) according to one of the preceding claims, characterized in that the standing cone (3) has several recesses (16) distributed around its circumference. Device (1) according to one of the preceding claims, characterized in that the housing (4) has at least one axial drainage channel (17). Device (1) according to one of the preceding claims, characterized in that the rotary cone (2) has a geometry-free surface on its cone surface (6) as a centrifugal geometry (15). Device (1) according to one of the preceding claims, characterized in that the rotary cone (2) has a wave-shaped geometry consisting of depressions (18) and elevations (19) on its cone surface (6) as a centrifugal geometry (15). Device (1) according to one of the preceding claims, characterized in that the device (1) further comprises a bearing (21) which is in direct contact with the lubricant flow (9) emerging from the gap (8).

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