DE102022132675B3 - Wet-running bevel gear differential and electrically operated axle drive train - Google Patents

Abstract

The invention relates to a wet-running bevel gear differential (1), in particular for an electrically operable axle drive train (20) of a motor vehicle (21), with a drive wheel (2) and a differential cage (3) which has an interior (4), the drive wheel ( 3) is non-rotatably connected to the differential carrier (3), a first bevel gear (5) and a second bevel gear (6), which are arranged coaxially to the drive wheel (2) and rotatable about a common output axis (7) within the interior (4) of the differential carrier (3), and within the differential carrier (3) at least one third bevel gear (8) rotatable about an axis of rotation (9) perpendicular to the output axis (7) with the first bevel gear (5) and the second bevel gear (6 ). Fluid reservoir (10) extends in the axial direction through the differential cage (3) and opens into the interior (4) of the differential cage (3), and the differential cage (3) has at least one fluid outlet channel (11) which extends from the interior (4 ) extends in the radial direction through the differential cage (3).

Description

The present invention relates to a wet-running bevel gear differential, in particular for an electrically operable axle drive train of a motor vehicle, with a drive wheel and a differential carrier, which has an interior, the drive wheel being non-rotatably connected to the differential carrier, a first bevel gear and a second bevel gear, which are coaxial arranged on the drive wheel and rotatably mounted about a common output axis within the interior of the differential carrier, and within the differential carrier at least one third bevel gear is rotatable about an axis of rotation perpendicular to the output axis and is in engagement with the first bevel gear and the second bevel gear, the third bevel gear is fixed to the differential carrier in the direction of rotation. The invention further relates to an electrically operable axle drive train.

Electric motors are increasingly being used to drive motor vehicles in order to create alternatives to combustion engines that require fossil fuels. Significant efforts have already been made to improve the suitability of electric drives for everyday use and to offer users the usual driving comfort.

A detailed description of an electric drive can be found in an article in the magazine ATZ 113th year, 05/2011, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold with the title: Highly integrative and flexible electric drive unit for electric Vehicles, which probably represents the closest state of the art. This article describes a drive unit for an axle of a vehicle, which includes an electric motor which is arranged concentrically and coaxially to a bevel gear differential, with a switchable 2-speed planetary gear set being arranged in the power train between the electric motor and the bevel gear differential, which is also is positioned coaxially to the electric motor or the bevel gear differential or spur gear differential. The drive unit is very compact and, thanks to the switchable 2-speed planetary gear set, allows a good compromise between climbing ability, acceleration and energy consumption. Such drive units are also referred to as e-axles or electrically operated drive trains.

From the DE 10 2010 048 837 A1 Such a drive device is known with at least one electric motor and at least one planetary differential which can be driven by a rotor of the electric motor, the planetary differential having at least one planetary carrier which is operatively connected to a rotor of the electric motor, first planetary gears and second planetary gears which are rotatably mounted on the planetary carrier, and a first sun gear and a second sun gear, each of which is operatively connected to an output shaft of the planetary differential. The first planet gears are in mesh with the first sun gear and each of the second planet gears is in mesh with the second sun gear and with one of the first planet gears. Furthermore, the sun gears are arranged coaxially with a rotation axis of the rotor.

From the publication EP 1 472 475 B1 A bevel gear differential is also known, as can also be used in e-axles, for example. The bevel gear differential comprises a differential housing, which can be driven via a ring gear firmly connected to the housing, as well as balancing gears, which are rotatably mounted in the differential housing, and additionally two planetary gears, which are also rotatably mounted in the differential housing, with which the balancing gears mesh and In this way the outputs of the bevel gear differential are formed.

When developing the electrical machines and transmissions intended for e-axles, there is a continuing need to increase their power densities, so that the necessary cooling, in particular of the electrical machines and transmissions, is becoming increasingly important. Due to the necessary cooling performance, hydraulic fluids, such as cooling oils, have become established in most concepts for removing heat from the thermally affected areas of an electrical machine and/or a transmission.

The gearboxes usually provided in the designated e-axles are usually lubricated with a gear oil, which is often also used as a cooling oil for the electric machine. In order to reliably bring the lubricant or cooling oil to the various lubricating or cooling points, it is known to form a hydraulic fluid circuit, for example in a bevel gear differential.

Such a wet bevel gear differential is a transmission component in a vehicle that ensures that the wheels of a vehicle turn evenly, even if they have different grip on the surface. This is particularly important on wet or slippery roads, as the differential prevents a wheel from spinning and the vehicle from skidding.

The wet bevel gear differential usually consists of two bevel gears opposite each other and connected by a gear. The wheels are able to rotate at different speeds to compensate for the difference in grip and traction on the wheels. This differential is therefore an important part of the vehicle drive and helps ensure that the vehicle can drive safely and in a controlled manner, even in unfavorable weather conditions.

As a rule, such wet-running bevel gear differentials have a cast or steel housing, also referred to as a differential cage. The differential baskets usually have relatively large openings on the circumference through which oil can get into the interior of the differential basket and whereby the rolling or rubbing contacts between the balance gear, thrust washer, balance gear bolt and axle shaft gear are lubricated. The outer wheel is connected next to the openings on the circumference of the differential cage, as these must be free to ensure lubrication. Furthermore, such a wet-running bevel gear differential usually splashes in an oil sump, which leads to corresponding splashing losses and higher operating noise.

The US 9,803,736 B2 shows a differential arranged in the direct torque path with pinions without a balancing star.

The WO 2021/ 137 278 A1 shows an electromechanical drive device for a motor vehicle with a bevel gear differential.

The US 3,138,222 A , the US 4,841,807 A , the JP H08-319 810 A , the US 7,892,131 B2 and the DE 21 50 676 A each show an oiling device for a differential gear.

The JP 2015- 048 890 A shows an oiling path in which the oil is fed through the gearbox housing, the bearing and finally to the bevel gear differential.

It is the object of the invention to provide a wet-running bevel gear differential that has improved lubrication and cooling performance. It is also the object of the invention to create an electrically operable axle drive train that is improved in terms of its cooling performance and longevity.

This object is achieved by a wet-running bevel gear differential, in particular for an electrically operable axle drive train of a motor vehicle, with a drive wheel and a differential carrier, which has an interior, the drive wheel being non-rotatably connected to the differential carrier, a first bevel gear and a second bevel gear, which are coaxial arranged to the drive wheel and rotatably mounted about a common output axis within the interior of the differential carrier, and within the differential carrier at least one third bevel gear is rotatable about an axis of rotation perpendicular to the output axis and is in engagement with the first bevel gear and the second bevel gear, the third Bevel gear is fixed to the differential carrier in the direction of rotation of the differential carrier, the differential carrier having at least one fluid supply channel which extends in the axial direction through the differential carrier starting from a fluid reservoir formed on the differential carrier and opens into the interior of the differential carrier, and the differential carrier has at least one fluid outlet channel , which extends from the interior in the radial direction through the differential carrier.

According to the invention, it is provided that the fluid reservoir is designed as an annular groove, the axis of rotation of which runs coaxially with the output axis, which can contribute to uniform oiling of the interior of the differential carrier.

According to the invention, a sleeve is arranged in the fluid reservoir, which acts as a hydraulic orifice in the fluid reservoir, which can help control the hydraulic flow into the interior of the differential carrier.

This allows a high level of precisely defined lubrication or cooling of the bevel gear differential inside the differential cage, even if the differential cage is almost closed and does not have any large openings, in order to make it particularly dimensionally stable and to protect the bevel gear differential against external mechanical influences and contamination . Furthermore, by eliminating an oil sump, splashing of the differential can also be avoided, which can help increase transmission efficiency.

Within the scope of the invention, a bevel gear differential is proposed which is suitable and/or designed for use in a vehicle. On the one hand, the bevel gear differential can be designed as a longitudinal differential, with which drive torque can be distributed over two axles of the vehicle. However, the bevel gear differential is preferably designed as a transverse differential or axle differential, with a drive torque being distributed over two output shafts of an axle. In alternative embodiments, the bevel gear differential can also be used to combine or distribute drive torques.

Vehicles or motor vehicles within the meaning of this registration are land vehicles that are: Machine power can be moved without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (passenger cars), trucks (lorries), mopeds, light vehicles, motorcycles, motor buses (KOM) or tractors.

The bevel gear differential according to the invention can be designed in particular for an electrically operable axle drive train of a motor vehicle. An electric axle drive train of a motor vehicle includes an electric machine and a transmission arrangement, the electric machine and the transmission arrangement forming a structural unit. The gear arrangement preferably comprises a bevel gear differential according to the invention.

In particular, it can be provided that the electric machine and the transmission arrangement are arranged in a common drive train housing. Alternatively, it would of course also be possible for the electric machine to have a motor housing and the gearbox to have a gearbox housing, with the structural unit then being able to be achieved by fixing the gearbox arrangement relative to the electric machine. This structural unit is sometimes also referred to as an e-axle.

The electric machine and the transmission arrangement can also be accommodated in a drive train housing. The drive train housing is at least intended to accommodate the electric machine and the transmission arrangement. The drive train housing is preferably formed from a metallic material, particularly preferably from aluminum, gray cast iron or cast steel, in particular by means of a primary molding process such as casting or die casting. In principle, however, it would also be possible to form the drive train housing from a plastic.

The drive train housing can particularly preferably have a pot-like basic shape, so that the electric machine and the transmission can be inserted into the drive train housing via the open end face thereof.

An electrical machine, as used in the electrically operable axle drive train, is used to convert electrical energy into mechanical energy and/or vice versa, and generally includes a stationary part called a stator, stator or armature and a rotor or rotor Part movably arranged relative to the stationary part.

In connection with the invention, the electrical machine can be designed as a radial or axial flux machine. In order to create an axially particularly compact axle drive train, axial flux machines are to be preferred.

The electric machine is intended in particular for use within an electrically operable drive train of a motor vehicle.

In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km/h, preferably greater than 80 km/h and in particular greater than 100 km/h can be achieved. The electric motor particularly preferably has a power greater than 30 kW, preferably greater than 50 kW and in particular greater than 70 kW. It is further preferred that the electric machine provides speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, most preferably greater than 12,500 rpm.

The transmission arrangement of the electric axle drive train can in particular be coupled to the electric machine, which is designed to generate a drive torque for the motor vehicle. The drive torque is particularly preferably a main drive torque, so that the motor vehicle is driven exclusively by the drive torque.

A gearbox is a housing to accommodate a gearbox. Its task is to guide existing shafts over the bearings and to grant the wheels the degrees of freedom they require under all loads, without hindering their rotation and possibly path movement, as well as to absorb bearing forces and supporting moments. A gearbox housing can be single-shell or multi-shell, that is, undivided or divided. In particular, the housing can also dampen noise and vibrations as well as safely absorb lubricant.

According to an advantageous embodiment of the invention, it can be provided that the fluid outlet channel runs eccentrically through the differential cage with respect to the axis of rotation of the third bevel gear. The advantage of this configuration is that the drive wheel in particular can be placed approximately in the middle of the differential cage, which can lead to bevel gear differentials that are particularly compact in axial terms. According to a further preferred development of the invention, it can also be provided in this context that the drive wheel has a first axial extension and the third bevel gear has a second axial extension, the first axial extension and the second axial extension having an axial extension Have a coverage range that is preferably between 60-100%.

Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the fluid supply channel runs axially parallel to the output axis of rotation. The axial course of the channel ensures that the lubricating fluid is evenly distributed throughout the interior of the differential carrier, thus reducing the friction of the moving parts. In addition, the axially parallel channel prevents the lubricating fluid from escaping from the differential under pressure or the influence of gravity, thus preventing leakage. This helps improve the performance and life of the differential.

Furthermore, the invention can also be further developed in such a way that the differential cage is designed to be essentially closed except for the fluid supply channel and the fluid outlet channel, so that no hydraulic fluid can penetrate uncontrollably into the interior of the differential cage. The closed differential cage has the advantage that it is more rigid and therefore has a higher load capacity. This results in improved power transmission and longer differential life. In addition, the closed differential cage reduces noise during operation.

According to a further preferred embodiment of the subject matter of the invention, it can be provided that the hydraulic fluid is supplied to the differential cage under pressure. An advantage of a bevel gear differential with pressurized lubricating oil is that the lubricating oil is better distributed in the differential cage, thus reducing the friction between the bevel gears. This improves the life of the differential and increases performance. It can also help the differential function more reliably under high temperatures and loads.

Finally, the object of the invention can also be achieved by an electric axle drive train of a motor vehicle, comprising an electric machine and a transmission arrangement which forms a structural unit with the electric machine and which comprises a wet-running bevel gear differential according to one of the preceding claims 1-6. The advantage of an electric final drive train with a gear arrangement that has a wet bevel gear is greater efficiency and performance with less heat generation compared to a dry gear. The wet-running bevel gear is also robust and durable and enables precise power transmission. In addition, the electric axle drive can improve the vehicle's energy efficiency and reduce CO2 emissions.

The invention will be explained in more detail below using figures without restricting the general idea of the invention.

• 1 ein Kraftfahrzeug mit einem elektrisch betriebenen Achsantriebsstrang in einer schematischen Blockschaltdarstellung, und
• 2 ein nasslaufendes Kegelraddifferential in einer Axialschnittansicht.

It shows:

• 1 a motor vehicle with an electrically operated axle drive train in a schematic block diagram, and
• 2 a wet bevel gear differential in an axial section view.

The 1 shows a wet bevel gear differential 1 as part of a transmission arrangement 23 in an electrically operable axle drive train 20 of a motor vehicle 21. Here, the transmission arrangement 23 is driven by the electric machine 22.

The bevel gear differential 1 has a drive wheel 2 and a differential carrier 3, which has an interior 4. The drive wheel 2 is connected to the differential carrier 3 in a rotationally fixed manner. A first bevel gear 5 and a second bevel gear 6 are arranged within the interior 4 of the differential carrier 3, which are aligned coaxially with the drive wheel 2 and are rotatably mounted about a common output axis 7.

Within the differential carrier 3, a third bevel gear 8 and a fourth bevel gear 28 are each rotatable about an axis of rotation 29 perpendicular to the output axis 7 and engage with the first bevel gear 5 and the second bevel gear 6. The third bevel gear 8 and the fourth bevel gear 28 are fixed to the differential carrier 3 in the direction of rotation. The bevel gears 8, 28 are rotatably mounted on the bevel gear shaft 14 and rotate about the axis of rotation 29.

The differential carrier 3 has at least one fluid supply channel 9, which extends in the axial direction through the differential carrier 3 starting from a fluid reservoir 10 formed on the differential carrier 3 and opens into the interior 4 of the differential carrier 3. The fluid supply channel 9 runs axially parallel to the output rotation axis 7. The hydraulic fluid 17 is supplied to the differential cage 3 under pressure.

A rolling bearing 16 is arranged on the differential cage 3 radially outside the fluid reservoir 10, which in particular enables a nested arrangement of the fluid reservoir 10 and the rolling bearing 16 and can thus contribute to an axially compact design of the bevel gear differential 1.

The differential carrier 3 also has at least one fluid outlet channel 11, which extends from the interior 4 in the radial direction through the differential carrier 3.

The differential cage 3 is essentially closed except for the fluid supply channel 9 and the fluid outlet channel 11, so that no hydraulic fluid 17 can penetrate into the interior 4 of the differential cage 3 in an uncontrolled manner.

In the exemplary embodiment shown, the fluid reservoir 10 is designed as an annular groove 18, the axis of rotation of which runs coaxially with the output axis 7. A sleeve 19 is arranged in the fluid reservoir 10 and functions as a hydraulic diaphragm in the fluid reservoir 10.

You can tell from the 2 good that the fluid outlet channel 11 runs eccentrically through the differential cage 3 with respect to the axis of rotation 29 of the third bevel gear 8. This makes it possible to position the drive wheel 2 approximately centrally on the differential carrier 3. The drive wheel 2 then has a first axial extension 12 and the third bevel gear 8 has a second axial extension 13, the first axial extension 12 and the second axial extension 13 having an axial coverage area 15.

The functionality of the bevel gear differential 1 is briefly explained below. The hydraulic fluid 17, for example a lubricating oil, is fed to the differential basket 3 from an unspecified oil channel and thus reaches the side of the fluid reservoir 10, which functions as an oil collecting geometry. The fluid reservoir 10 has a geometric undercut that can be formed directly in the differential basket 3, or for manufacturing reasons, as in the embodiment shown 2 , also by an additional component, in this case by a simple sleeve 19. At speed, the hydraulic fluid 17 in the fluid reservoir 10 is accelerated radially outwards. The fluid supply channels 9 designed as axial bores in the differential cage 3 form an oiling path into the interior of the bevel gear differential 1. For manufacturing reasons, these bores are parallel to the output axis of rotation 7 of the bevel gear differential 1, but can also be arranged at a slight angle if necessary.

In order to be able to implement the fluid reservoir 10 in terms of installation space in the differential cage 3, a roller bearing 16 with a correspondingly large diameter is selected. This allows the rolling bearing 16 and the fluid reservoir 10 to be nested radially.

The deoiling of the bevel gear differential 1 is realized through a fluid outlet channel 11 designed as a bore on the circumference of the bevel gear differential 1. This hole is not made on the largest inside diameter of the differential carrier 3. This means that a certain amount of residual oil always remains in the differential basket 3 and ensures a basic supply of oil.

Since there are no large openings on the circumference of the differential carrier 3 for oiling and mounting the bevel gear differential 1, the drive wheel 2 of the bevel gear differential 1 can be placed approximately in the middle of the differential carrier 3. The connection between the drive wheel 2 and the differential carrier 3 is not interrupted even in this central position, since the usual openings are not present.

The invention is not limited to the embodiments shown in the figures. The foregoing description is therefore not to be viewed as limiting but rather as illustrative. The following patent claims are to be understood as meaning that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of other features. If the patent claims and the above description define 'first' and 'second' features, this designation serves to distinguish two similar features without establishing a ranking.

Reference symbol list

1

Bevel gear differential

2

drive wheel

3

Differential basket

4

inner space

5

bevel gear

6

bevel gear

7

Output axle

8th

bevel gear

9

Fluid supply channel

10

Fluid reservoir

11

Fluid outlet channel

12

extension

13

extension

14

bevel gear shaft

15

Coverage area

16

roller bearing

17

Hydraulic fluid

18

Nut

19

sleeve

20

Axle drive train

21

motor vehicle

22

electric machine

23

Gear arrangement

28

bevel gear

29

Axis of rotation

Claims (7)

Wet-running bevel gear differential (1), in particular for an electrically operable axle drive train (20) of a motor vehicle (21), • with a drive wheel (2) and • a differential cage (3) which has an interior (4), the drive wheel (2) is rotatably connected to the differential carrier (3), • a first bevel gear (5) and a second bevel gear (6), which are arranged coaxially to the drive wheel (2) and rotatable about a common output axis (7) within the interior (4) of the Differential carrier (3) are mounted, and • within the differential carrier (3) at least one third bevel gear (8) rotatable about a rotation axis (29) which is perpendicular to the output axis (7) with the first bevel gear (5) and the second bevel gear (6 ) is engaged, the third bevel gear (8) being fixed to the differential carrier (3) in the direction of rotation, characterized in that • the differential carrier (3) has at least one fluid supply channel (9) which extends from one on the differential carrier (3) formed fluid reservoir (10) extends in the axial direction through the differential cage (3) and opens into the interior (4) of the differential cage (3), • the differential cage (3) has at least one fluid outlet channel (11) which extends from the interior (4) extends in the radial direction through the differential cage (3), • a rolling bearing (16) is arranged on the differential cage (3) radially outside the fluid reservoir (10), • the fluid reservoir (10) as an annular groove (18 ) is designed, the axis of rotation of which runs coaxially to the output axis (7) and • a sleeve (19) is arranged in the fluid reservoir (10), which acts as a hydraulic diaphragm in the fluid reservoir (10). Bevel gear differential (1). Claim 1 , characterized in that the fluid outlet channel (11) runs eccentrically through the differential cage (3) with respect to the axis of rotation (29) of the third bevel gear (8). Bevel gear differential (1). Claim 1 or 2 , characterized in that the drive wheel (2) has a first axial extent (12) and the third bevel gear (8) has a second axial extent (13), the first axial extent (12) and the second axial extent (13) being one have axial coverage area (15). Bevel gear differential (1) according to one of the preceding claims, characterized in that the fluid supply channel (9) runs axially parallel to the output axis of rotation (7). Bevel gear differential (1) according to one of the preceding claims, characterized in that the differential basket (3) is designed to be essentially closed except for the fluid supply channel (9) and the fluid outlet channel (11), so that no hydraulic fluid (17) enters the interior in an uncontrolled manner ( 4) of the differential cage (3). Bevel gear differential (1) according to one of the preceding claims, characterized in that the hydraulic fluid (17) is supplied to the differential cage (3) under pressure. Electric axle drive train (20) of a motor vehicle (21) comprising an electric machine (22) and a transmission arrangement (23) which forms a structural unit with the electric machine (22) and which comprises a wet-running bevel gear differential (1) according to one of the preceding claims.

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