Electric axle drive axle with drum brakes

Abstract

The invention relates to an electrically operated axle drive train (1) for a motor vehicle (motor vehicle) with an electric machine (2), wherein the electric machine (2) has two torque outputs to each transmit a torque to a drive wheel (3) of the motor vehicle, wherein at least one drum brake (4) is provided on at least one of the torque outputs of the electric machine (2) and is thus connected in the torque flow from the electric machine (2) to the respective drive wheel (3) in such a way that the torque can be subjected to a braking torque before being transmitted to the drive wheel (3).

Description

[0001] The invention relates to an electrically operated axle drive train according to the preamble of claim 1 for a motor vehicle (MV) such as a passenger car (PC) or a commercial vehicle (CV), for example a truck (TKW), with an electric machine designed, for example, as a radial flux machine or as an axial flux machine, wherein the electric axle drive axle has two torque outputs in order to transmit a torque to a drive wheel of the motor vehicle.

[0002] According to current technology, a vehicle's wheels are often driven by an electric drive axle. An electric motor, which can be a radial or axial flux motor, drives a front axle driveshaft and a rear axle driveshaft via a two-stage or single-stage transmission and a differential, such as a bevel gear or spur gear differential. The driveshafts are rigidly connected to the wheels. Drum brakes are also rigidly connected to and integrated into the wheels. A common complaint is the significant emission of abrasion in the form of particulate matter, which is unintentionally released into the environment. Poor driving dynamics are also frequently criticized in known e-axle solutions.

[0003] Furthermore, prior art of the applicant exists in the field of the present invention. The relevant publication DE 10 2023 111 274 A1 describes an electrically operated axle drive train for a motor vehicle, comprising an electric motor designed as a radial flux machine for driving the motor vehicle. The electric motor is connected to the input of a differential gear via a first gear stage, transmitting torque.The differential gear has a first output for connecting a first vehicle wheel and a second output for connecting a second vehicle wheel. The electric motor has a stator with an internally rotating first rotor and an externally rotating second rotor. The first and second rotors are rotationally fixed to each other and connected to an input of the first gear stage. The input of the differential gear is torque-transmitting and connected to an output of the first gear stage. The axle drive train shown is a particularly compact design. Here, a double-acting radial flux machine drives the driveshaft via a single-stage transmission.

[0004] However, this solution can still be optimized in terms of driving dynamics, environmental compatibility and use of installation space.

[0005] Against this background, the object of the present invention is to eliminate or at least mitigate the disadvantages known from the prior art.

[0006] In a generic electrically operated axle drive train, this is solved by having at least one drum brake at at least one of the torque outputs and integrating it into the torque flow from the electric machine to the relevant drive wheel in such a way that the torque can be subjected to a braking torque before being transferred to the drive wheel, with the drum brake(s) being attached to a housing of the electric machine.

[0007] One could also say that the drum brakes are mounted at the respective outputs of the electric drive axle and brake the vehicle via the drive shafts onto the wheels. This allows for a particularly compact integration of the drum brakes into the central electric drive axle, especially through the use of a compact, double-acting radial flux machine with high torque and only one transmission stage and one differential – for example, a spur gear differential – which reduces the unsprung mass at the wheels and increases the integration of the drive axle.

[0008] Advantageous embodiments are claimed in the dependent claims and are explained in more detail below.

[0009] It is advantageous for the drum brake to be mounted on the housing of the electric motor. Mounting the drum brake to the housing advantageously results in a compact design. The high, typically unsprung masses associated with arranging the brakes on or near the drive wheels are reduced by arranging the drum brakes within the electric axle drive train. Furthermore, arranging the drum brakes on the housing ensures easy access to the brakes, particularly in an advantageous embodiment where the drum brakes are formed preferably partly by the drum brake itself and preferably partly by the housing of the electric motor and / or the electric axle drive train. The proportions of the brake drum and the housing can be variably designed and modified according to the principles of the invention.A particular advantage is the design of the brake drum and housing as halves, so that the drum brake consists of at least two halves. The housing half thus serves as a cover side of the brake unit. For this technical purpose, instead of the housing, other sheet metal arrangements or housing assemblies, or solid structural elements connected to the drive shaft, are also conceivable and included in the invention.

[0010] The transition between the two parts of the drum brake designed in this way is preferably contactless. In this respect, it is technically advantageous if a gap is provided between the outer surfaces defining the parts. This gap is preferably designed such that fluids, in particular, can flow through it. The flow path is advantageously designed. This advantageous design of the gap and the flow path will be further detailed in the subsequent explanation of advantageous embodiments.

[0011] The drum brake, and thus also the brake drum, is advantageously positioned directly in front of or behind the housing of the electric motor or the electric axle drive train. The spatial references expressed by the directional terms "in front" and "behind" are defined by and based on the front and rear axles of the respective vehicle. In the illustrated embodiment, it is also advantageous if the brake drum is connected to at least one drive shaft of the electric axle drive train in a rotationally fixed and removable manner. Technically advantageous and simple assembly methods for these connecting elements include screws. Alternatively, the brake drums can be attached using hinges that ensure a rotationally fixed connection and are removable from their predetermined position by being rotatable or hinged.The technical advantage of the rotationally fixed and, to a certain extent, removable / movable connection of the brake drum to the electric axle drive axle / drive shaft / output shaft lies in the fact that the drum brakes can be easily replaced or inspected thanks to the simple accessibility provided by removing the driveshaft and loosening the connection / opening the brake drum. This includes, in particular, replacing the brake shoes due to wear and tear, as well as replacing the brake drum by loosening one or more bolts per connecting element. Disassembly of the electric axle drive train is advantageously unnecessary due to the straightforward removal of the driveshaft.

[0012] The number of drum brakes on the electric axle drive train can be implemented and varied in any configuration. Integrating a multitude of drum brakes into the electric axle drive train is conceivable within the scope of the invention. In particular, symmetrical arrangements of the drum brakes in front of and behind the electric motor and the housing, as well as two-sided arrangements of the brake drums and drum brakes radially to the electric axle drive train / drive shaft, are advantageous with regard to the effect and distribution of the abrasive torque. Beyond the arrangement of the brake shoes near the respective drum brake, the arrangement of at least one or more hydraulic cylinders and / or electromechanical actuators is conceivable and implied within the scope of the present invention.

[0013] Furthermore, it is advantageous if the drum brake is connected to a driveshaft in a torque-transmitting manner, which in turn is connected to the drive wheel in a torque-transmitting manner. The transmission of output torques / braking torques generated by the drum brakes is advantageously achieved through the torque transmission of the drum brake, the driveshafts of the front and rear axles, and the drive wheels guided on the respective front and rear axles. Also conceivable within the scope of the present invention is the transmission of the braking torque generated by the drum brakes to a drive shaft of the electric axle drive train, which in turn is connected to one or more driveshafts and the drive wheels in a torque-transmitting manner.

[0014] It is also advantageous if a drum brake is present at each of the two torque outputs. The arrangement of the drum brakes at the two torque outputs allows for a technically advantageous transmission of the braking torque to the drive wheels of the vehicle. The braking torque is transmitted to a first drive wheel and a second drive wheel, which together represent the drive wheels of the front axle and the rear axle, respectively. Viewed in the direction of the front axle, the first drive wheel is the right-hand drive wheel and the second drive wheel is the left-hand drive wheel. It is also conceivable that at least one of the torque outputs of the electric motor has a drum brake and is integrated into the torque flow from the electric motor to the respective drive wheel in such a way that the torque can be subjected to a braking torque before being transferred to the drive wheel.

[0015] It has proven advantageous for the electric motor to be designed as a double-acting radial flux machine. Designing the electric motor as a double-acting radial flux machine allows for a more compact design of the electric axle drive train. This is technically advantageous because the double-acting radial flux machine, with its internal and external rotors, delivers high torque despite its compact dimensions. This allows the torque to be transmitted via a single gear stage to one or more drive shafts and then to the drive wheels of the respective rear or front axle.Due to the high electrical and mechanical efficiencies achievable in this way, as well as the low mass of the axle drive train, this has a particularly low energy consumption, which is a technical advantage and can therefore contribute to a long vehicle range.

[0016] Furthermore, it is advantageous if the electric motor has a first, single-stage transmission followed by a differential. The first, single-stage transmission advantageously converts the torque generated by the electric motor and allows it to be directly transmitted to the downstream differential. This advantageously compact arrangement then enables the differential to directly equalize the rotational speeds at a predetermined torque distribution between the right and left drive wheels. Both spur gear differentials and bevel gear differentials are advantageous designs for the differential, as they are cost-effective and ensure a constant gear ratio.

[0017] Designing the gearbox as a single-stage gearbox allows for a technically advantageous, particularly compact design. Multi-stage gearboxes are also conceivable within the scope of the invention.

[0018] Furthermore, it is advantageous if the differential gear of the electric motor provides the first and second differential outputs. By providing these outputs, the connection of a first and second drive wheel of the respective rear axle and / or front axle of the vehicle to and via the first and second differential outputs, coupled to a drive shaft, can be implemented in a technically advantageous manner. This design thus contributes to a more compact axle drivetrain design, which is both obvious and beneficial.

[0019] Furthermore, it is advantageous if at least one of the drive wheels has suspension, or if both drive wheels each have their own suspension. Suspension effectively absorbs shocks caused by the movement of the drive wheels on the ground during travel.

[0020] Furthermore, it is advantageous if the gap formed between the brake drum and the housing according to one of the embodiments described above is continuously sealed for fluids by a sealing element. Preferably, this sealing element is designed as a gasket, and in particular as a labyrinth seal. By designing the seal as a non-contact shaft seal, and preferably as a labyrinth seal, the sealing effect for the gap can be advantageously achieved by increasing the flow path and thus the flow resistance for the fluid entering the gap towards the drum brake or the fluid exiting it, such as condensation. Because the labyrinth seal is friction-resistant, wear-resistant, and abrasion-resistant due to its advantageous non-contact design, advantages arise with regard to the service life of the seal.In this embodiment, it is fundamentally conceivable that the edges of the seal are located on only one or both / multiple sides of the gap. Extending the flow path via more complex geometries for the seal design is also conceivable. In particular, the interlocking of shaped elements such as edges or shoulders of the stationary halves of the drum brake, and thus of the brake drum and the housing, is also considered for sealing the gap. Because the escape of fluid from the interior of the drum brake via the gap is only technically possible via an extended flow path, the removal of brake dust contained in the fluid from the drum brake is limited, as the brake dust is deposited along the fluid's flow path due to its higher density and flow resistance.

[0021] In connection with the brake dust generated on drum brakes, it is also advantageous to have a brake dust collection reservoir in the brake drum. This reservoir is located within the drum brake, and in particular within the interior of the drum brake formed by the brake drum and the housing, or technically comparable embodiments thereof, as described in the present invention. This prevents or at least reduces the release of brake dust into the environment, thus reducing particulate matter emissions. Furthermore, alternative configurations for the brake dust collection reservoir within the preferred half of the housing or the interior are conceivable, and advantageous embodiments of the reservoir that are integrated or integrable into the housing are particularly relevant.

[0022] The invention is explained in more detail below with the aid of drawings. These show: Fig. 1 an electric drive axle with double-acting radial flux machine (DRFM) and integrated drum brake as a schematic diagram, and Fig. 2 an electric drive axle with double-acting radial flux machine (DRFM) and integrated drum brake as a 2D sectional view in longitudinal section.

[0023] The figures are purely schematic and serve only to illustrate the invention. The same elements are identified by the same reference symbols.

[0024] In the Fig. Figure 1 shows a schematic diagram of an electric drive axle 1 according to the invention, comprising an electric motor 2. This electric motor 2 is designed to drive at least two wheels 3 of a motor vehicle. It has integrated drum brakes 4, which are designed in a particularly compact form.

[0025] The torque from the drum brake 4 is transmitted to the wheels 3 via drive shafts 5. A gear stage 6 is located in the drive axle 1. A differential gear 7 is also used.

[0026] There is also a suspension 8 on the wheels 3 to improve driving dynamics. The drum brake 4 uses a brake drum 9, which is partially enclosed by a housing 10 of the electric motor 2. There is a gap 11 between the housing 10 and the brake drum 9. Additionally, sealing elements 12 and exactly one reservoir 13 for collecting brake dust are installed / designed for each drum brake 4.

[0027] In the Fig. 2. The constructive connection of the brake drum 9 to an output shaft 15 is achieved using screws 14. Brake dust collects in the interior 16 of the reservoir 13 during operation.

[0028] The electric drive axle 1 consists of a double-acting radial flux machine 2, a transmission stage 6, and a differential 7. The double-acting radial flux machine 2 is very compact and, due to its high torque, only uses one transmission stage 6. The differential 7 is in Fig. 1 a bevel gear differential is formed.

[0029] In a second embodiment, the differential 7 can be designed as a spur gear differential.

[0030] The drum brakes 4 are mounted at the respective outputs of the electric drive axle 1 and brake the vehicle via drive shafts 5 onto the drive wheels 3. A drive wheel 3 is understood to be a wheel of a front axle or a rear axle. The elimination of the brakes 4 on the drive wheels 3 makes the reduction of the unsprung mass at the wheel 3 technically advantageous and can be schematically illustrated. Fig. 1 evident. If the particularly compact design is not required, the use of other types of electric machines 2 such as single-acting radial flux machines or axial flux machines and also multi-stage transmissions / several transmission stages 6 is conceivable and advantageous.

[0031] In the Fig. Figure 2 shows the electric drive axle 1 with a double-acting radial flux machine as the electric machine 2 and integrated drum brakes 4 in a 2D cross-sectional view. The electric drive axle 1 according to the invention has integrated drum brakes 4 and is designed in a particularly compact form. The electric machine 2, in its configuration as a double-acting radial flux machine, is advantageously very short and, due to its high torque, uses only one transmission stage 6.

[0032] Differential 7 is designed as a spur gear differential. Another advantageous embodiment of differential 7 is a bevel gear differential.

[0033] The drum brakes 4 are mounted at the respective outputs of the electric drive axle 1 and brake the vehicle via the drive shafts 5 onto the wheels 3. The brake drums 9 are connected to the output shafts 15 in a rotationally fixed and removable manner via the screws 14. Inside the brake drums 9 are components of the drum brakes 4 according to the prior art, such as brake shoes or hydraulic cylinders, which are integrated into the housing 10 of the electric drive axle 1.

[0034] The integration of electromechanical actuators into the brake drums 9 is also conceivable. The housings 10 thus form one half of the drum brake 4. A seal 12, advantageously designed as a labyrinth seal, is provided between the brake drums 9 and the housing 10, which advantageously allows water to flow in and, in particular, also to drain away. In addition to the brake drums 9, reservoirs 13 for brake dust are provided at predetermined locations in the housing 10 that are technically suitable for the intended function. Furthermore, in another embodiment, the integration of the reservoirs into the interior space 16 formed by the respective brake drum 9 and the housing 10 is conceivable. However, replacing the brake drums 9 and the brake shoes is still relatively easy by removing the drive shafts 5, although significantly less brake wear can be expected with electric drives. Reference symbol list 1 Electrically operated axle drive train 2 Electric machine 3 Drive wheel / wheel 4 drum brakes 5 Cardan shaft 6 gear stages 7 Differential gears 8 Suspension 9 brake drum 10 cases 11 column 12 Sealing element / gasket / labyrinth seal 13 Reservoir / collection reservoir for brake dust 14 screws 15 Output shaft / Drive shaft 16 Interior

Claims

[1] Electrically operated axle drive train (1) for a motor vehicle comprising an electric machine (2) with a first gear stage (6) and a differential gear (7) downstream thereof, wherein the electric machine (2) is designed as a double-acting radial flux machine with an inner and an outer rotor, wherein the electric machine (2) transmits a torque to a drive wheel (3) of the motor vehicle via the differential gear (7) downstream thereof, characterized by , that at least one drum brake (4) is present at at least one of the torque outputs of the differential gear (7) and is thus bound in the torque flow from the electric machine (2) to the relevant drive wheel (3), that the torque can be subjected to a braking torque before being transferred to the drive wheel (3), wherein the drum brake(s) (4) is / are attached to a housing (10) of the electric machine (2). [2] Electrically operated axle drive train (1) according to claim 1, characterized by , that the drum brake (4) is connected to a drive shaft (5) in a torque-transmitting manner, which in turn is connected to the drive wheel (3) in a torque-transmitting manner. [3] Electrically operated axle drive train (1) according to one of claims 1 or 2, characterized by , that a drum brake (4) is present at each of the two torque outputs. [4] Electrically operated axle drive train (1) according to claim 1, characterized by , that the differential gear (7) of the electric machine (2) provides the first differential output and the second differential output. [5] Electrically operated axle drive train (1) according to any one of claims 1 to 4, characterized by , that at least one of the drive wheels (3) has a suspension (8) or both drive wheels (3) each have their own suspension (8). [6] Electrically operated axle drive train according to any one of claims 1 to 5, characterized by , that a gap (11) formed by a brake drum (9) and the housing (10) is sealed permeably for fluids via a sealing element (12). [7] Electrically operated axle drive train according to one of the preceding claims, characterized by , that a collection reservoir (13) for brake dust is provided in the drum brake (4).

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