Drivetrain with at least one electrically driven axle and hydrodynamic brake for this

Abstract

The invention relates to a drive train (100) and a hydrodynamic brake (9) for this drive train for a motor vehicle, in particular a truck, with at least one electrically driven drive axle (1) by means of at least one electric motor (4, 5) and two drive shafts (2, 3) each containing at least one drive wheel (6, 7). In order to operate the motor vehicle economically and with a weight-reduced design, at least one electric motor (4, 5) arranged close to the wheel is assigned to each drive shaft (2, 3) and a hydrodynamic brake (9) is arranged between the drive shafts (4, 5).

Description

[0001] The invention relates to a drive train and a hydrodynamic brake for the same for a motor vehicle, in particular a truck, having at least one drive axle electrically driven by at least one electric machine with two drive shafts each containing at least one drive wheel.

[0002] Motor vehicles, such as trucks or buses, with electric drives are increasing in number. Similar to motor vehicles with combustion engines, electrically driven drivetrains can, in addition to the vehicle's service brakes and the recuperation of electrical energy from kinetic energy by means of the electric motor(s), also have a hydrodynamic brake (retarder) to decelerate the vehicle while preserving the service brakes when recuperation is insufficient.

[0003] For example, DE 10 2017 202 322 A1 discloses a method for implementing a driver-side deceleration function, among other things, using a hydrodynamic brake. The underlying drivetrain contains two drive shafts, such as a propeller shaft, with drive wheels, which are driven by an electric motor via a transmission and an unspecified differential. The hydrodynamic brake is connected between the electric motor and the transmission with the drive shafts and the differential.

[0004] Further prior art is referred to DE 10 2019 006 668 A1, DE 10 2020 101 157 A1 and DE 10 2017 005 470 A1.

[0005] The object of the invention is to further develop an electric drive train and a hydrodynamic brake therefor. In particular, the object of the invention is to design an electric drive train in a simple manner while reducing the number of components and to propose a correspondingly designed hydrodynamic brake for this purpose. This object is achieved by the subject matter of claims 1 and 4. The claims dependent on claims 1 and 4 represent advantageous embodiments of the subject matter of claims 1 and 4.

[0006] The proposed drive train is intended for a motor vehicle, in particular a truck or bus. The electric drive train contains at least one electric drive axle having two drive shafts, to which one drive wheel or several drive wheels, for example two designed as twin wheels, are attached. The electric drive axle can be designed, for example, as a rigid axle and accordingly sprung and shock-absorbed relative to a vehicle chassis. Alternatively, the wheels can be individually suspended and shock-absorbed relative to the drive wheels and, if necessary, in the case of a steered axle, attached to the drive shafts via an articulated connection. The drive wheels are driven by the electric motors. For example, at least one electric motor is arranged close to the wheel on each drive shaft, which drives the drive wheel or wheels of the respective drive shaft.A transmission that can be switched over several gear stages, for example a planetary gear, can be provided between the drive shaft and at least one electric motor.

[0007] A hydrodynamic brake is arranged between the drive shafts, for example, on the end faces opposite the drive wheels. This hydrodynamic brake is located in the usual position of a differential to compensate for different speeds of the drive wheels of the two drive shafts, for example, during cornering. In addition to its location, this hydrodynamic brake also fulfills the properties of a differential, eliminating the need for a separate differential and allowing the entire design of an electric drive axle to be proposed with fewer components, less assembly effort, lower weight, and lower manufacturing costs.

[0008] According to an embodiment of the electric drive train according to the invention, a decoupling device, for example a separating clutch, a freewheel, and / or a synchronization device, can be arranged between the hydrodynamic brake and the drive wheels. The decoupling devices can be designed separately or in conjunction with the hydrodynamic brake. For example, at least one of the separating clutches can be accommodated in a housing of the hydrodynamic brake and operated wet by means of the operating fluid of the hydrodynamic brake. When both decoupling devices are actuated, the hydrodynamic brake can be completely separated from the drive wheels, so that each drive shaft can be driven independently of the other by the associated at least one electric motor.Furthermore, by activating only one decoupling device, the corresponding drive shaft can be braked by the hydrodynamic brake, while the other drive shaft remains unbraked or can even be driven. Activating both or only one decoupling device can be advantageous due to the reduced flow resistance of the hydrodynamic brake during drive of the electric drive axle and / or to achieve dynamic driving effects, for example, on a smooth or slippery road surface, cornering, downhill drift, and / or the like, which only affects the drive wheels or the drive wheel of a drive shaft.

[0009] The hydrodynamic brake can be provided during coasting for the sole purpose of decelerating the motor vehicle and / or in addition to the service brakes and / or recuperating electric motors. Depending on the charge level of at least one on-board accumulator that can be charged in recuperation mode to power the motor vehicle and / or supply additional electrical consumers in the motor vehicle, some, all, or none of the electric motors can be activated in recuperation mode during deceleration of the motor vehicle. Due to the use of the hydrodynamic brake, the service brakes of the motor vehicle can be dimensioned for less braking force and can therefore be designed smaller and more cost-effectively.

[0010] The proposed hydrodynamic brake is used, in particular, in the described drive train between two drive shafts of an electrically driven drive axle. The hydrodynamic brake contains a housing in which two stators arranged opposite one another and fixedly connected to the housing are connected to form a stator unit. The stators or the stator unit are connected to the housing, for example, by means of a soldered, welded, plug-in connection, or the like. A mutual arrangement of the stators means that the blades of the stators point away from one another and are hydrodynamically effectively coupled to oppositely arranged blades of a rotor that is rotationally fixedly connected to a drive shaft.

[0011] The rigid coupling of the drive shafts, or rather their parts connected to the hydrodynamic brake, is advantageously achieved by the stator unit being rotatably mounted on both drive shafts. One stator can be mounted on a stub shaft of one drive shaft, and the other stator can be mounted on a stub shaft of the other drive shaft, either rotatably and, if necessary, axially fixed or compensating for axial play. Furthermore, the rotors are mounted rotatably relative to the housing and sealed to the outside.

[0012] The housing accommodates the stators and rotors in one or more chambers, sealed from the outside. To actuate the hydrodynamic brake, the housing is automatically filled with operating fluid, for example oil or water, via at least one inlet or supply line by a driver of the motor vehicle or a control system. To deactivate the hydrodynamic brake, the operating fluid is drained from the housing via at least one outlet or discharge line. The operating fluid preferably flows in from the radial outside or, for example, from the radial inside via at least one hollow-bored drive shaft. At least one outlet is spaced apart from the at least one inlet. The at least one outlet can be formed in different chambers for the rotors, preferably with controllable throttles, in order, for example, to make the braking torque on the drive shafts the same or different.

[0013] According to an advantageous embodiment of the hydrodynamic brake, at least one inflow of operating fluid can be provided into a chamber of the stator unit, which chamber is connected by means of openings in the stators to chambers having outflows between the housing and the rotor.

[0014] Alternatively, in the hydrodynamic brake, rotors and stators can be accommodated in a single common chamber, with an inflow of operating fluid in the area of ​​one rotor and its outflow in the area of ​​the other rotor.

[0015] An exchange of operating fluid can occur, for example, by means of suction at an inlet using the Venturi effect. For example, an inlet can be provided in the housing into a chamber between the housing and the rotor, the distance between which decreases towards at least one opening arranged radially inside the rotor, wherein a gap radially outside the inlet between the housing and the rotor is set smaller than the minimum distance radially inside the inlet.

[0016] In summary, the following details can be advantageous for a hydrodynamic brake, either individually or in combination: - Stator is firmly connected to the housing, for example by means of soldering or welding, a spline connection and / or the like. - Stator unit consists of two stators that are firmly coupled to each other and each functionally interacts with a rotor. - Supply of operating fluid into the stator unit via at least one central inflow opening, preferably from the radial outside or from the radial inside via a hollow shaft. - When supplying operating fluid from the outside, the shells of the stators can either be spaced apart from each other or flow channels can be provided between them if the operating fluid is to be guided radially within a contact point of the two shell rear sides. - Supply of operating fluids into the torus interior, if necessary via hollow blades. - Merging of two separate chambers, each containing a rotor, by means of recesses in the shells of the stators. - Partial merging of two separate chambers, each containing a rotor, by inserting a permeable partition instead of sealed stator shells. This allows pressure equalization between the two parts of the hydrodynamic brake assigned to the drive shafts, so that equal braking torques act on both drive shafts. - Instead of a central inlet opening, separate inlets can be provided for the two chambers assigned to the drive shafts. This has the advantage of allowing the inflow and thus the braking torque to be specifically influenced. - Preferably adjustable throttles can be provided at the two outlet openings of the two chambers in order to be able to specifically adjust the braking torque on the two drive shafts. - Use of the Venturi effect to suck in, for example, cold operating fluid into the corresponding chamber. - Decoupling devices, such as clutches, freewheels and synchronisation devices, can be provided between rotors and electric machines.

[0017] The invention is based on the Fig. 1 to 4 are explained in more detail. These show: Fig. 1 an electric drive train in schematic representation, Fig. 2 a section through a hydrodynamic brake, Fig. 3 a section through a brake system which is different from the hydrodynamic brake of the Fig. 2 modified electrodynamic brake and Fig. 4 a detail of an electrodynamic brake according to the Fig. 2 and Fig. 3 to exploit the Venturi effect.

[0018] The Fig. Figure 1 shows the electric drive axle 1 as part of the electric drive train 100 of a motor vehicle, for example, a truck or bus, in a schematic representation with the two drive shafts 2, 3, on each of which electric motors 4, 5 are arranged, which drive the drive wheels 6, 7 rolling on the roadway 8. The two drive shafts 2, 3 are rotationally coupled to the hydrodynamic brake 9 at their end faces opposite the drive wheels 6, 7. Decoupling devices 10, 11, here separating clutches 12, 13, are arranged between the electric motors 4, 5 and the hydrodynamic brake 9.

[0019] The hydrodynamic brake 9 has two stators 15, 16 connected opposite one another to the stator unit 14, whose blades 17, 18 each face the blades 21, 22 of the rotors 19, 20 and, under the influence of operating fluid, for example oil or water, act to hydrodynamically brake the drive wheels 6, 7 during rotation in the overrun mode of the drive train 100 and when the separating clutches 12, 13 are closed, i.e., actuated. For this purpose, the rotors 19, 20 are connected in a rotationally fixed manner to the drive shafts 2, 3, and the stators 15, 16 are connected in a rotationally fixed manner to a fixed housing (not shown). During traction operation of the drive train 100, the operating fluid is drained from the hydrodynamic brake 9 and / or the separating clutches 12, 13 are opened. By specifying the filling of the hydrodynamic brake 9, the braking torque can be adjusted.

[0020] The hydrodynamic brake 9 can support the recuperation of the electric motors 4, 5 and / or service brakes of the motor vehicle or can exclusively brake the motor vehicle.

[0021] The Fig. 2 shows the upper part of the hydrodynamic brake 9 arranged around the rotation axis d of the Fig. 1 in section. The two stators 15, 16 with their blades 17, 18, like lamellae, are connected radially inward to the stator ring 23, for example, soldered or welded, and radially outward to the stator sleeve 24, such as soldered or welded, thus forming the stator unit 14. The stators 15, 16 are firmly connected to the housing 25, such as soldered or welded, here by means of the stator sleeve 24. The stators 15, 16 are rotatably and preferably axially fixedly mounted on the drive shafts 2, 3 by means of the stator ring 23 and the rotary bearings 26, 27.

[0022] The rotors 19, 20 are mounted on the respective drive shafts 2, 3 by means of gears 28, 29, in a rotationally fixed manner and with limited axial displacement. Their blades 21, 22 face the blades 17, 18, forming a gap. The rotors 19, 20 are rotatably mounted relative to the housing 25 by means of rotary bearings 30, 31 and sealed to the outside by means of ring seals 32, 33. The rotors 19, 20 are further axially and rotatably mounted relative to the housing 25 and the stator ring 23, and thus relative to the stator unit 14, by means of axial bearings 34, 35, 36, 37, for example, needle bearings.

[0023] The interior of the hydrodynamic brake 9 is divided into three chambers 38, 39, 40. Chamber 38 is assigned to the stator unit 14 and has the inlet 41 for the operating fluid on its radial outside. The mutually facing rear sides of the stators 15, 16 can be axially spaced from each other to ensure sufficient flow of operating fluid or can have corresponding axially overlapping passages 42, for example, axially overlapping embossments or the like.

[0024] From chamber 38, the operating fluid flows evenly into chambers 39, 40 via passages 43, 44 arranged circumferentially in stators 15, 16. The operating fluid is drained again via drains 45, 46 when hydrodynamic brake 9 is deactivated. A possibly different braking torque acting on drive shafts 2, 3 can be adjusted by unevenly draining the operating fluid from drains 45, 46. Apart from this, in this embodiment, the hydrodynamic brake 9 is fundamentally designed to act equally on both drive shafts.

[0025] The Fig. 3 shows the upper part of the brake 9 arranged around the rotation axis d, opposite the hydrodynamic brake 9 of the Fig. 2 slightly modified and simplified hydrodynamic brake 9a in section. In the hydrodynamic brake 9a, the stator sleeve 24 ( Fig. 2) is omitted; the stators 15a, 16a are connected radially outwardly directly to the housing 25a. The shells of the stators 15a, 16a are connected to each other in one piece.

[0026] Furthermore, the interior of the hydrodynamic brake 9a forms a single common chamber 38a for the stators 15a, 16a and for the rotors 19a, 20a. The inlet 41a supplies the operating fluid. From there, it flows through at least one opening 47a and the recesses 48a between the stators 15a, 16a into the entire chamber 38a and from there, during shutdown or operation with reduced braking torque, to the outside via the outlet 45a.

[0027] The Fig. 4 shows a detail of a brake system which is different from the hydrodynamic brakes 9, 9a of the Fig. 2 and Fig.3 modified hydrodynamic brake 9b, in which the operating fluid supplied to chamber 38b utilizes the Venturi effect, which is generally advantageous when the operating fluid is cold. The operating fluid is supplied from the inlet 41b in the housing 25b into the chamber 38b. Due to the narrowing width of the chamber 38b in the direction of arrow 49b toward the opening 50b of the rotor 19b, the operating fluid is sucked through the opening 50b by means of the Venturi effect when the rotor 19b rotates relative to the housing 25b. Outside the inlet 41b, the gap 51b is set with a smaller width along the arrow 49b. List of reference symbols 1 drive axle 2 drive shaft 3 drive shaft 4 Electric machine 5 Electric machine 6 drive wheel 7 Drive wheel 8 Roadway 9 hydrodynamic brake 9a hydrodynamic brake 9b hydrodynamic brake 10 Uncoupling device 11 Uncoupling device 12 Separating clutch 13 Separating clutch 14 Stator unit 15 Stator 15a Stator 16 Stator 16a Stator 17 shovels 18 shovels 19 Rotor 19a Rotor 19b Rotor 20 rotors 20a rotor 21 shovel 22 shovels 23 Stator ring 24 Stator sleeve 25 housings 25a housing 25b housing 26 rotary bearings 27 rotary bearings 28 Gearing 29 Gearing 30 rotary bearings 31 rotary bearings 32 ring seal 33 Ring seal 34 thrust bearings 35 thrust bearings 36 thrust bearings 37 thrust bearings 38 Chamber 38a Chamber 38b Chamber 39 Chamber 40 chambers 41 Inflow 41a Inflow 41b tributary 42 passage 43 passage 44 passage 45 Drain 45a drain 46 Drain 47a Opening 48a recess 49b Arrow 50b opening 51b gap 100 Powertrain d axis of rotation

Claims

[1] Drive train (100) for a motor vehicle, with at least one drive axle (1) electrically driven by at least one electric machine (4, 5) with two drive shafts (2, 3) each containing at least one drive wheel (6, 7), characterized by in that at least one electric machine (4, 5) arranged close to the wheel is assigned to each drive shaft (2, 3), and a hydrodynamic brake (9, 9a, 9b) is arranged between the drive shafts (2, 3), wherein a decoupling device (10, 11) in the form of a separating clutch is arranged between the hydrodynamic brake (9, 9a, 9b) and the drive wheels (6, 7), wherein the separating clutches (12, 13) are designed in such a way that when both separating clutches (12, 13) are actuated, the hydrodynamic brake (9, 9a, 9b) is completely separated from the drive wheels (6, 7). [2] Drive train (100) according to claim 1, characterized bythat the hydrodynamic brake (9, 9a, 9b) is provided for sole and / or additional use in coasting mode of the motor vehicle to service brakes and / or recuperating electric machines. [3] Drive train (100) according to one of claims 1 to 2, characterized by that the hydraulic brake (9, 9a, 9b) is provided for a function of a differential between the two drive shafts (2, 3). [4] Hydrodynamic brake (9, 9a, 9b) according to one of claims 1 to 3, characterized by in that in a housing (25, 25a, 25b) of the hydrodynamic brake (9, 9a, 9b) two stators (15, 15a, 16, 16a) arranged opposite one another and fixedly connected to the housing (25, 25a, 25b) are connected to form a stator unit (14), to which a rotor (19, 19a, 19b, 20, 20a) is hydrodynamically effectively coupled, said rotor being arranged opposite a respective stator (15, 15a, 16, 16a) and being connected in a rotationally fixed manner to one of the drive shafts (2, 3). [5] Hydrodynamic brake (9, 9a, 9b) according to claim 4, characterized by that the stator unit (14) is rotatably mounted on both drive shafts (2, 3). [6] Hydrodynamic brake (9a) according to claim 4 or 5, characterized by that at least one inlet (41) for operating fluid is provided in a chamber (38) of the stator unit (14), which chamber (38) is connected by means of passages (43, 44) in the stators (15, 16) to chambers (39, 40) having outlets (45, 46) between the housing (25) and the pump wheels (19, 20). [7] Hydrodynamic brake (9a) according to claim 4 or 5, characterized by that pump wheels (19a, 20a) and stators (15a, 16a) are accommodated in a single common chamber (38a), wherein an inlet (41a) for operating medium is provided in the region of one rotor (19a) and an outlet (45a) for the operating medium is provided in the region of the other rotor (20a). [8] Hydrodynamic brake (9b) according to one of claims 4 or 5, characterized bythat the operating fluid is sucked in via an inlet (41b) by means of the Venturi effect. [9] Hydrodynamic brake (9b) according to claim 8, characterized by that in the housing (25b) an inflow (41b) into a chamber (38b) between the housing (25b) and the rotor (19b) is provided, the distance between which decreases in the direction of at least one opening (50b) radially inside the inflow (41b) in the rotor (19b), wherein radially outside the inflow (41b) between the housing (25b) and the rotor (19b) a gap (51b) smaller than a minimum distance between the housing (25b) and the rotor (19b) radially inside the inflow (41b) is set.

Images