Gear unit with a planetary gear with oiling vanes and an oil guide channel as well as an electric axle with an electric motor and a gear unit

Abstract

The invention relates to a transmission unit (1) for a motor vehicle with a planetary gear (2) comprising a planet (3), a planet carrier (4) supporting the planet (3), a ring gear (5) into which the planet (3) engages, and a housing (6). The housing (6) has an oil guide channel (7) at a circumferential position, which extends radially outward away from a rotational space (8) of the planet (3). The planet (3) has, on at least one side surface (9), oil conveying vanes (10) for conveying an oil flow, which run radially outward and extend axially from the side surface (9). The invention also relates to an electric axle with an electric motor (21). The electric motor (21) is connected to an input of the planetary gear (2) of such a transmission unit (1).

Description

[0001] The invention relates to a transmission unit for a motor vehicle with a planetary gear, which in turn has (at least) one (preferably three) planets / planetary gear, a planet carrier carrying the planet, a ring gear into which the planet engages, and a housing / housing part, wherein the planet has oil conveying vanes / oil conveying lamellas on at least one side surface for conveying an oil flow / fluid, which oil conveying vanes run radially outwards and extend axially from the side surface.

[0002] In this field of the invention, the prior art published as US 2025 / 0 163 999 A1, which was filed as a US patent application and received the file number 18 / 516905, is located. US 2025 / 0 163 999 A1 presents a system for lubrication of a differential using vanes formed on a side surface of planets of an upstream planetary gear.

[0003] The US patent, published under US 12 160 160 B1 with the application number 18 / 338753, describes a lubrication concept in which oil, which is carried along by planets in the direction of rotation of the planet carrier, is distributed in the transmission chamber.

[0004] DE 10 2022 001 354 B3 shows an electric drive device for a motor vehicle, in particular for a motor vehicle preferably designed as a passenger car. This means that the motor vehicle, in its fully manufactured state, has the electric drive device and can be driven, in particular purely electrically, by means of the electric drive device. The electric drive device has a main housing, also simply referred to as a housing, which is designed or constructed, for example, as a cast part, and is therefore preferably produced by casting. The main housing delimits a receiving area, in particular directly, wherein the receiving area is divided by wall regions of the main housing into a first sub-region and a second sub-region. The second sub-region is at least partially separated from the first sub-region, in particular fluidically, and thus encapsulated.The second subregion is at least partially surrounded by the first subregion. Because the subregions are at least partially separated from one another, in particular fluidically, by the aforementioned wall regions of the main housing and thus encapsulated from one another, the wall regions are arranged between the subregions.

[0005] US 2023 / 0 050 981 A1 shows a drive unit with an oil supply.

[0006] WO 2022 / 270 217 A1 shows a unit with improved heat exchange.

[0007] US 2023 / 0 193 979 A1 discloses a planetary gear for a planetary transmission, comprising a gear body with a first planetary gear end face and a second planetary gear end face, a planetary gear axis defining a planetary gear rotational axis of the planetary gear, and a first bearing portion and a second bearing portion, wherein the first bearing portion projects beyond the first planetary gear end face and the second bearing portion projects beyond the second planetary gear end face, wherein at least one planetary gear bore extending coaxially or parallel to the planetary gear rotational axis extends at least partially through the planetary gear axis. A variety of different methods for conveying or pumping fluids are known. This can be done actively using pumps or similar methods, or passively as a waste product of a system's movement. Active conveying systems are usually associated with increased costs, which is why passive systems are preferred.Such a passive system can be implemented by utilizing the rotation in a planetary gear. For this purpose, oil present in the housing of the planetary gear can be extracted at a circumferential position. Due to the rotation, the oil is pressed, thrown, entrained, or displaced into a withdrawal point. The flow rate and direction depend on the rotation speed of the planetary gear. Nevertheless, the oil should be pumped even at low rotation speeds and provide a mass flow sufficient for the respective application.

[0008] The oil is usually extracted at top dead center or at a side wall on the side which follows bottom dead center in the direction of rotation of the planet carrier. This means that the oil is pushed in front of the planets mounted on the planet carrier or is carried along in the direction of rotation of the planet carrier. This effect of pumping the oil in the direction of rotation of the planet carrier is counteracted by the oil being pumped due to the rotation of the planets against the direction of rotation of the planet carrier. This counteracting effect is caused in particular by a pumping effect of the gear teeth of the planets. At high rotation speeds, i.e. in particular at an engine speed above 4000 rpm, the pumping effect in the direction of rotation of the planet carrier predominates, whereas at low rotation speeds, i.e. in particular at an engine speed below 4000 rpm, the pumping effect against the direction of rotation of the planet carrier predominates.Due to the two opposing effects, the resulting conveying capacity is low, especially at low rotation speeds.

[0009] The delivery capacity of a passive oil pumping system using the movement of the planets in the direction of rotation of the planet carrier to or into the extraction point is too low at low rotation speeds to ensure efficient cooling and / or lubrication.

[0010] It is therefore the object of the present invention to improve the production of oil, to increase the production rate or at least to provide a sufficient production rate even at low rotation speeds.

[0011] This is achieved according to the invention in a generic transmission unit in that the planet has, on at least one side surface, oil conveying vanes for conveying an oil flow, which run radially outwards and extend axially starting from the side surface.

[0012] It should be noted that in addition to a simple block-like shape, the oil production vanes can also be turbine-blade-shaped or flow-optimized in another way.

[0013] The oil pump vanes can be designed either as a single piece with the planetary gear or as multiple parts. The oil pump vanes can be formed together with the planetary gear, reshaped, or formed during machining, or they can be added to the planetary gear as a separate component or components.

[0014] It is also conceivable that the oil conveyor blades are formed on a separate carrier body which is attached to the planet.

[0015] Instead of the smooth or straight side surfaces of the planet, oil-feeding vanes are now formed on at least one side surface.

[0016] This increases the power transmission between the planetary gear and the oil, allowing the planetary gear to transfer more rotational energy to the oil. This increases the planetary gear's pumping action against the direction of rotation of the planet carrier, i.e., in the direction of rotation of the planet. The oil pumping vanes amplify the pumping action of the planetary gear teeth, so that the pumping action against the direction of rotation of the planet carrier, particularly at low rotation speeds, significantly outweighs the pumping action in the direction of rotation of the planet carrier. The gear unit's oil is thus pumped against the direction of rotation of the planet carrier, at least in sections, along the side surface.

[0017] Advantageous embodiments are claimed in the subclaims and are explained in more detail below.

[0018] It is advantageous if both sides have oil-propelling vanes. This can further increase the pumping efficiency of the planetary gear.

[0019] An advantageous embodiment is characterized in that the planet is designed as a double / double-stage planet (i.e., a planetary gear with two differently dimensioned, axially offset toothings), wherein the rotational space is defined by a largest stage of the planet with a toothing of the largest diameter. The use of double planets enables higher gear ratios per planetary set and therefore a saving in installation space and components compared to several simple / single-stage planetary sets. It is particularly advantageous if the oil guide channel is formed radially outside the ring gear of the planet with the toothing of the smallest diameter.

[0020] If the planetary gear is designed as a double planetary gear, both sides of the largest stage can have oil-feeding vanes. This further increases the planetary gear's pumping efficiency. The gear teeth of the largest stage can reach a lower point in the housing than the smallest stage, allowing them to penetrate deeper into the oil, or even penetrate it at a lower oil level, thus pumping the oil more efficiently.

[0021] It is advantageous if the oil pump vanes are formed radially within the root circle of the planetary gear. This prevents the oil pump vanes from interfering with the toothing during production. Any excessive stresses in a sharp-edged transition between the oil pump vanes and the planetary gear can be located away from the toothing. Particularly in the case of oil pump vanes that are not integrally formed with the planetary gear, weakening of the planetary gear material can occur away from the toothing due to drilling, clamping, soldering, or welding points.

[0022] An advantageous embodiment is characterized in that the oil guide channel is crescent-shaped in sections. This means that the oil guide channel can be curved in sections and taper, at least in sections, along its length. This minimizes flow losses and optimally captures the pumped oil.

[0023] An advantageous embodiment is also characterized in that the oil guide channel is designed in an operating position of the gear unit above an axis of the planetary gear, particularly in the upper third of the rotational space. This allows the oil to be tapped at a position where it may have absorbed a great deal of kinetic energy due to prolonged contact with the oil conveying vanes, but at the same time, it can also reach this position even at low rotational speeds.

[0024] If the housing has an inlet area in which a distance from a rotational axis of the planetary gear increases in the circumferential direction, i.e. which widens radially in the circumferential direction, merges / opens into the oil guide channel and begins below the rotational axis, in particular in the operating position of the gear unit, flow losses can be further minimized and the delivery rate can increase.

[0025] An advantageous embodiment is characterized in that the housing has a partially scythe-shaped outlet channel / connecting channel, into which the oil guide channel merges / leads and, in particular, ends at the level of a lowest point of the rotation chamber or merges into another channel. This means that the outlet channel can have a smaller curvature, i.e., a larger radius, than the oil guide channel. The course of the outlet channel can, in particular, approximate the inner and / or outer contour of the housing. This allows the thickness of a housing wall to be kept low, while the outlet channel runs within the wall.

[0026] The housing can be constructed in two or more parts and the oil guide channel and / or the inlet area and / or the outlet channel can be formed in a housing flange, in particular as a depression or recess.

[0027] The invention ultimately also relates to an electric axle / drive train with a transmission unit according to the invention, wherein an electric motor is connected to an input of the planetary gear of the transmission unit according to the invention.

[0028] An advantageous embodiment is characterized in that an oil flow through the oil guide channel is used for cooling a component and / or a structural unit.

[0029] Such a design is particularly suitable for purely electrically powered vehicles, especially for use in inner-city areas.

[0030] The invention is explained in more detail below with the aid of a drawing. It shows: Fig. 1 isometric view of a first embodiment of a gear unit according to the invention with output-side housing part, Fig. 2 isometric view of the gear unit with output side housing part and oil flow, Fig. 3 a side view of the gear unit with output side housing part, Fig. 4 a side view of the gear unit with motor-side housing part, Fig. 5 isometric view of a largest stage of a double planet, and Fig. 6 Isometric view of a smallest stage of a double planet.

[0031] The figures are merely schematic and serve only to clarify the invention. The same elements are designated by the same reference numerals.

[0032] In the Fig. 1 shows a first embodiment of a gear unit 1 according to the invention. The gear unit 1 comprises a planetary gear 2 with three double planets 3, a planet carrier 4, a ring gear 5 and a housing 6. The planets 3 are mounted on the planet carrier 4 and are partially encompassed by it. The planets 3 mesh with a toothing in the ring gear 5. The ring gear 5 is connected to the housing 6 via a spline. The housing 6 is designed in two parts, wherein Fig. 1 only an output-side housing part is shown.

[0033] An oil guide channel 7 is formed in a flange of the housing 6. This channel extends radially outward from a circumferential position, i.e., an inner side of the housing 6. The oil guide channel 7 begins outside a rotational space 8 of the planets 3 and extends away from it.

[0034] Oil conveying vanes 10 are formed on the side surfaces 9 of the planets 3. These vanes extend radially outward and, starting from the side surface 9, extend in the axial direction.

[0035] The oil conveying vanes 10 serve to convey an oil flow into or towards the oil guide channel 7 and can be designed either as a single piece with the planet 3 or as a separate component.

[0036] The oil conveying vanes 10 are formed on both side surfaces 9 of the largest stage 11 of the planetary gear 3. The smallest stage 12 of the planetary gear 3 engages the ring gear 5 and has no oil conveying vanes 10. The oil conveying vanes 10 end radially within the root circle of the largest stage 11 of the planetary gear 3. The radial extension of the oil conveying vanes 10 is small compared to the diameter of the largest stage 11 of the planetary gear 3, i.e. the oil conveying vanes 10 are formed exclusively on an outer circular ring of the side surface 9.

[0037] The oil conveying vanes 10 move / convey a fluid present in the gear unit 1 in the direction of rotation 24 of the planets 3, i.e. opposite to a direction of rotation 22 of the planet carrier 4.

[0038] The oil guide channel 7 is crescent-shaped / arch-shaped, while its width decreases in sections as it extends away from the rotation chamber 8. The oil guide channel 7 deflects a fluid flow by approximately 180°. In an operating position (intended installation position viewed in the gravitational field), the oil guide channel 7 begins above an axis 14 of the planetary carrier 4. More precisely, the oil guide channel 7 begins in the upper third of the rotation chamber 8.

[0039] An inlet area 15 is formed in front of the oil guide channel 7, i.e., radially inside and in the circumferential direction of the housing 6 in the direction of rotation 22 of the planet carrier 4. The inlet area 15 begins below the axis 14 and merges into the oil guide channel 7. This expands increasingly radially in the circumferential direction, i.e., the distance of a housing wall of the housing 6 from the axis 14 increases counter to the direction of rotation 22 of the planet carrier 4, forming the inlet area 15.

[0040] The oil guide channel 7 opens into a partially scythe-shaped outlet channel 16. The output-side housing part in Fig. 1 forms only a part of the outlet channel 16.

[0041] For a better understanding of the axial direction and radial direction, the two directions are referenced with the reference numerals 17 and 18.

[0042] In the Fig. 2 is the gear unit from Fig. 1 with oil 23. The oil flow represents a condition that occurs at an engine speed below 4000 rpm. The flow of oil 23 in the direction of rotation 24 of the planetary gears 3 predominates over the flow against the direction of rotation 22 of the planetary gear carrier 4. This creates an oil flow toward and into the oil guide channel 7.

[0043] In the Fig. 3 is the gear unit 1 with the output side housing part made of Fig. 1 is shown in a side view. Viewed from the direction of axis 14, the radial expansion of the inlet area 15, opposite to the direction of rotation 22 of the planet carrier 4, is particularly evident.

[0044] In the Fig. 4 shows the transmission unit 1 with a motor-side housing part of the housing 6. The oil guide channel 7, which is partially covered by the housing 6, is also formed in the motor-side housing part. The outlet channel 16 is formed in a flange of the housing 6 and runs circumferentially parallel to the inside of the housing 6. The outlet channel 16 merges into another channel 20 at the level of a lowest point 19 of the rotation chamber 8.

[0045] For the sake of completeness, it should be noted that the transmission unit 1 under consideration is preferably part of an electric axle (electric axle drive unit), which is not further illustrated here for the sake of clarity. This electric axle further comprises an electric motor 21, which is connected to the housing 6 and is preferably coupled to an input of the transmission unit 1.

[0046] In the Fig. 5 and Fig.6 shows the double planet 3. Oil conveying vanes 10 are formed on both side surfaces 9 of the largest stage 11. List of reference symbols 1 gear unit 2 planetary gears 3 Planet 4 planet carriers 5 ring gear 6 housings 7 Oil guide channel 8 Rotation space 9 side surfaces 10 oil production bucket 11 largest level 12 smallest level 13 - 14 Axis 15 Inlet area 16 Outlet channel 17 Axial direction 18 Radial direction 19 lowest point 20 channels 21 Electric motor 22 Direction of rotation of planet carrier 23 Oil 24 Direction of rotation planet

Claims

[1] Gear unit (1) for a motor vehicle with a planetary gear (2) which has a planet (3), a planet carrier (4) carrying the planet (3), a ring gear (5) into which the planet (3) engages, and a housing (6), wherein the housing (6) has an oil guide channel (7) at a circumferential position which extends radially outwards from a rotation space (8) of the planet (3), characterized by that the planet (3) has oil conveying vanes (10) for conveying an oil flow on at least one side surface (9), which oil conveying vanes (10) run radially outwards and extend axially starting from the side surface (9). [2] Gear unit (1) according to claim 1, characterized by that both side surfaces (9) have oil conveying vanes (10). [3] Gear unit (1) according to claim 1, characterized bythat the planet (3) is designed as a double planet, wherein the rotation space (8) is defined by a largest stage (11) of the planet (3) with a toothing with a largest diameter. [4] Gear unit (1) according to claim 3, characterized by that both side surfaces (9) of the largest stage (11) of the planet (3) have oil conveyor blades (10). [5] Gear unit (1) according to one of claims 1 to 4, characterized by that the oil conveying vanes (10) are formed radially within a root circle of the planet (3). [6] Gear unit (1) according to one of claims 1 to 5, characterized by that the oil guide channel (7) is partially crescent-shaped. [7] Gear unit (1) according to one of claims 1 to 6, characterized bythat the oil guide channel (7) is designed in an operating position of the gear unit (1) above an axis (14) of the planetary gear (2), in particular in the upper third of the rotation space (8). [8] Gear unit (1) according to one of claims 1 to 7, characterized by that the housing (6) has an inlet region (15) in which a distance of a housing wall of the housing (6) to an axis (14) of the planetary gear (2) increases in the circumferential direction, ie which widens radially in the circumferential direction, which inlet region (15) merges into the oil guide channel (7) and begins below the axis (14) in the operating position of the gear unit (1). [9] Gear unit (1) according to one of claims 1 to 8, characterized bythat the housing (6) has a partially scythe-shaped outlet channel (16) into which the oil guide channel (7) merges and which reaches to the level of a lowest point (19) of the rotation space (8) and from there merges into a further channel (20). [10] E-axle with an electric motor (21), wherein the electric motor (21) is connected to an input of the planetary gear (2) of the transmission unit (1) according to one of claims 1 to 9, characterized by that an oil flow through the oil guide channel (7) is used for cooling a component and / or a structural unit.

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