CENTRALLY DRIVED TRAILER AXLE

Description

[0001] The present invention relates to a centrally driven axle, in particular for use in a trailer.

[0002] Trailer axles driven by wheel hub motors are already known in the art. In this design, each wheel is driven by a wheel hub motor mounted directly on the wheel. The main problem is the large amount of space required for these motors. This necessitates either widening the trailer's track width, which is often restricted by legal regulations, or reducing the distance between the axle supports, thus lowering the spring center and negatively impacting driving stability. Furthermore, the use of wheel hub motors is also expensive, as usually at least two motors are installed at the axle ends and connected to a central pressure source via numerous long hydraulic lines.These long hydraulic lines are not only heavy, but also take up installation space, which is particularly limited in the area of ​​the wheel suspensions.

[0003] DE 10 2015 122 801 A1 relates to a driven axle arrangement comprising two half-shafts for driving a respective wheel hub and a differential gear provided between the half-shafts for distributing a drive torque of a motor to the two half-shafts.

[0004] WO 2017 / 106620 A1, WO 2017 / 193130, US 2011 / 0259657 A1 and WO 2017 / 144905 A1 also each relate to axle units with motors, where these motors can each drive two drive shafts.

[0005] The object of the present invention is to provide a driven axle, in particular for trailers, which on the one hand ensures a high degree of driving stability and on the other hand requires only a small installation space and incurs low costs.

[0006] This problem is solved by means of an axle unit according to claim 1, wherein preferred embodiments result from the dependent claims.

[0007] According to the invention, an axle unit, particularly for trailer axles such as semi-trailer axles, comprises a motor and two drive shafts, each drive shaft having an input section and an output section. The motor is designed to exert torque on the two drive shafts via the input sections, and the output section of each drive shaft is designed to drive one wheel directly or indirectly. An axle unit according to the invention is preferably used in trailers, which are characterized in particular by the fact that they are designed to be towed by a towing vehicle during normal driving operation. The sole motor of the axle unit is an energy converter arranged within a housing, which converts potential energy, such as electrical energy or voltage, or fluid pressure, into kinetic energy, in particular torque.The motor according to the present invention differs from a gearbox in that, in the normal operating state in which the motor drives the drive shafts, the incoming energy is not coupled into the motor by means of a torque or a transverse movement. The drive shafts of the axle unit serve to transmit a torque between the input section of the respective drive shafts and the output section. The input section is the section of the drive shafts that serves to receive or absorb a torque from the motor, either directly or indirectly. The input section is therefore, in particular, the section that is oriented towards the motor and is preferably located a maximum of 20 cm away from the motor, so that, due to the limited space available between the input sections and the motor for additional components, a compact axle unit is achieved.The output section of the drive shaft, on the other hand, serves to transmit torque to a wheel, either directly (via intermediate elements) or indirectly. The input and / or output sections are preferably designed such that the torque transmission is positively engaged, allowing for the reliable and slip-free transmission of highly fluctuating torques. The input and output sections can therefore preferably be designed as part of a splined connection, keyway connection, splined shaft connection, toothed shaft connection, polygonal shaft connection, tapered connection, or spur gear connection. It is particularly preferred if the input and output sections are identical in design, thus saving costs due to standardized production steps.The inventive design of the axle unit ensures that only one connection for the power supply is required to drive two wheels and that driving stability can be increased by allowing the axle's support or bearing points to be separated far from each other, thus in particular increasing the spring center. The spring center is the distance between the axle's support or bearing points, by means of which it is supported on a vehicle frame or body.

[0008] According to the invention, the motor is arranged between the two entry sections of the drive shafts. This results in the axle unit requiring only a small installation space. "Between" in this context means that at least some areas of the motor are geometrically arranged between the two entry sections of the drive shafts. In other words, the motor is intersected by the longitudinal axes of the drive shafts.

[0009] In a preferred embodiment, the motor is a hydraulic motor. This achieves a high power density of the axle unit, thus saving weight. Additionally, the use of a hydraulic motor has the advantage that existing sensors are not affected by electromagnetic fields that could be caused by an electric motor. Preferably, the hydraulic motor is an axial piston motor, enabling stepless speed control in a cost-effective manner. Alternatively, and more preferably, the motor can also be a radial piston motor, which results in a particularly long service life because this type of hydraulic motor experiences especially low piston loads.

[0010] Preferably, the motor is a double-row hydraulic motor with at least two output shafts that can be decoupled from each other. A double-row hydraulic motor is particularly characterized by the fact that the two independently powered energy converter rows are located within a single motor. In other words, this means that the two rows of the motor are housed in a common casing. Advantageously, the two rows of the double-row hydraulic motor are capable of exerting different speeds or torques on the two output shafts. The output shafts are the shafts of the motor designed to transfer the initial energy converted into kinetic energy from the motor. "Decoupling" in this context means that the two output shafts of the motor are capable of rotating at different speeds.Thanks to the two decoupled output shafts, the axle unit is able to ensure minimal tire wear even when cornering with a particularly small turning circle.

[0011] Advantageously, the drive shafts and / or the output shafts of the motor are aligned parallel and / or concentrically to each other. This allows for a particularly space-saving axle unit. In this context, concentricity means, among other things, that the relevant shafts rotate around the same axis.

[0012] Alternatively, and preferably, a differential is arranged between the output shaft of the motor and the input sections of the drive shafts. This allows for the cost-effective minimization of tire wear during cornering. The differential is, in particular, a planetary gear set, which advantageously has four bevel gears. In this context, "between" means that the motor does not directly transmit torque to the input sections, but rather that torque is first transmitted indirectly or directly from the motor to a differential, which then exerts torque on the input sections, either directly or indirectly. Alternatively, and preferably, the axle assembly can also be designed without a differential. This results in a particularly cost-effective axle assembly.

[0013] Preferably, the motor is an electric motor, in particular having two independently decoupled output shafts. The use of an electric motor has the advantage of achieving particularly high efficiencies and, in particular, the fact that the power supply does not suffer from the disadvantage of leaks that can lead to environmental damage. Compared to a hydraulic motor, the effort required for the power supply is significantly less, since in the simplest case only one cable needs to be laid instead of at least two hydraulic lines, as the electric motor can be directly connected to the vehicle's chassis. Preferably, the electric motor is a DC motor, such as a servo motor. This allows the vehicle's electrical system, especially that of the trailer in which the axle unit is installed, to be used in a particularly cost-effective manner.Alternatively, the electric motor can also be an AC motor, particularly an asynchronous motor. The advantage of an AC motor is that it does not suffer from brush wear and can withstand short-term, significant overloads.

[0014] Advantageously, the motor's output shaft(s) is / are hollow, with the drive shaft sections extending at least partially into the hollow output shaft(s). This results in a particularly compact axle assembly. Specifically, the output shafts extend at least 2 cm into the hollow interior of the output shaft(s). The output shafts can be completely hollow or only partially hollow. Preferably, the torque is transmitted directly from the hollow motor output shaft to the drive shaft sections via a positive-locking connection, thus reducing the number of components in the axle assembly and saving costs. In other words, the output shaft can function as a hub for the drive shaft sections.For a smooth and stable torque transmission, it is particularly advantageous if the axis of rotation of at least one wheel driven by the motor has the same axis of rotation as the motor's output shaft. This helps to avoid or reduce torsional vibrations in the axle assembly.

[0015] Advantageously, the drive shafts are designed to be rotationally symmetrical. This prevents imbalances. Rotationally symmetrical in this context does not mean that the entry and exit sections must also be rotationally symmetrical, but rather that the engagement geometries ensure a positive torque transmission. Preferably, the drive shafts are at least partially, and ideally completely, hollow inside. This design not only saves weight but also improves the responsiveness of the axle assembly.

[0016] Advantageously, the drive shafts are identical. In other words, this means that the two drive shafts of the axle unit are interchangeable. Because the two drive shafts are identical, costs can be saved, particularly in manufacturing and spare parts supply.

[0017] Preferably, the drive shafts are arranged symmetrically to a plane, and preferably the engine is intersected by the plane of symmetry or is located a maximum of 20 cm away from it. The plane or plane of symmetry can, in particular, be the median plane of the vehicle in which the axle assembly is installed. The median plane is the plane midway between the distal outer surfaces of the vehicle, preferably having a normal oriented parallel to the axis of rotation of the vehicle's wheels. In other words, the median plane is the plane of the vehicle between the distal right and distal left wheels of an axle. The symmetrical arrangement of the drive shafts and, in particular, the engine, results in a particularly advantageous weight distribution of the axle assembly.The phrase "the plane of symmetry intersects the motor" means that the imaginary plane of symmetry intersects, or at least touches, the motor housing. "Distanced" in this context means that the part of the motor closest to the plane of symmetry is no more than 20 cm away from it.

[0018] According to the invention, the drive shafts are each made in one piece. This results in a particularly cost-effective and low-wear design of the drive shafts. "One piece" means, among other things, that there are no joints or other connecting elements that join different components of the drive shaft together. This ensures a particularly reliable and stable transmission of rotary motion.

[0019] Preferably, at least one of the drive shafts is arranged in a hollow axle tube. Preferably, however, both drive shafts are each arranged in a hollow axle tube. The hollow axle tube serves in particular to absorb the bending moments that occur when the vehicle is supported. This allows the drive shafts of the axle unit to be designed to be particularly thin, since they are only subjected to torsional loads. Preferably, the hollow axle tube remains stationary, i.e., it does not rotate. To achieve a particularly quiet and compact bearing arrangement, the drive shafts, or the drive shaft, are supported in the hollow axle tube(s) by means of plain bearings. Alternatively, and preferably, the drive shafts, or the drive shaft, can also be supported in the axle tube by means of rolling bearings, resulting in a particularly cost-effective axle unit with high efficiency.Preferably, a wheel hub, which serves to mount the driven wheel, is supported or mounted on the axle tube by means of hub bearings. Advantageously, these hub bearings are rolling bearings. This mounting of the wheel hub on the axle tube allows for a minimal installation space requirement. It is particularly preferred if two axle tubes are present, with the motor of the axle unit arranged (geometrically) between the two axle tubes and connected to them, especially directly. This results in the axle unit forming an independent drive unit that can be assembled as a complete unit, thus saving assembly costs. Advantageously, each of the hollow axle tubes is supported against the vehicle frame by a longitudinal control arm and / or a spring element.

[0020] Advantageously, a freewheel is arranged between the output shaft and the wheel hub. The freewheel acts primarily as a kind of overrunning clutch, so that torque is only transmitted from the drive shaft to the wheel when the wheel hub rotates at a lower speed than the drive shaft, and no torque is transmitted when this is not the case. Among other things, the use of a freewheel offers a cost-effective way to reduce tire wear when cornering. "Arranged between" means that the output shaft can transmit torque to the freewheel, either directly or indirectly, and the freewheel is designed to transmit torque to the wheel or wheel hub, either directly or indirectly. Alternatively, the freewheel can also be an integral part of the wheel hub. The crucial point is that the freewheel is located between the output shaft and the driven wheel.The wheel hub is, in particular, the hub that receives or supports the driven wheel.

[0021] Preferably, a switchable clutch is arranged between the drive shaft and the wheel hub. Switchable means that the clutch can assume at least two states. A first state is characterized by the fact that torque transmission between the engine and the wheel hub can take place. In the second state of the clutch, however, torque transmission between the engine and the wheel hub is not possible. Preferably, the clutch is a friction-fit clutch, which results in a particularly cost-effective clutch. Alternatively, preferably, it can also be a positive-locking clutch, in particular a dog clutch. The advantage of a positive-locking clutch lies particularly in the fact that it ensures reliable torque transmission even under dynamic fluctuations. Particularly preferably, the output section of the drive shaft forms part of the clutch.This allows for a particularly small installation space requirement. In one exemplary embodiment, this can be achieved by the drive shaft's output section forming an axial toothing that engages with a corresponding axial toothing in the wheel hub or a transmission plate, whereby the drive shaft is axially displaceable, enabling engagement and disengagement.

[0022] In a preferred embodiment, the clutch is hydraulically actuated. Hydraulic actuation allows for particularly space-saving clutch operation. Preferably, the supply lines required for the hydraulic actuation are routed through the hollow drive shaft. This type of hydraulic supply is particularly space-saving and saves installation space. To reduce the number of components, it is advantageous for the clutch to be supplied with hydraulic fluid via the same supply line as the hydraulic motor of the axle unit.

[0023] Preferably, the clutch is designed such that it does not transmit torque in the event of a pressure drop in the hydraulic supply. This measure increases the reliability of the axle unit, as a pressure drop in the hydraulic supply indicates an insufficient power supply to the motor. Automatic switching to the clutch's torque-free state can be achieved, among other things, by using an energy storage device, such as a spring.

[0024] Further advantages and features of the invention will become apparent from the following description with reference to the accompanying figures. Individual features disclosed in the illustrated embodiments may also be used in other embodiments, unless this has been expressly excluded. The figures show: Figure 1 shows an embodiment of an axle unit according to the invention; Figure 2 shows a detail from a further embodiment of an axle unit according to the invention.

[0025] The Figure 1Figure 1 shows an axle unit 1 comprising a motor 2 that drives the drive shafts 3 and 4 via the inlet sections 5. The drive shafts 3 and 4, in turn, drive the transmission plates 10 via the outlet sections 6. These transmission plates, in turn, drive each wheel hub 9 via a frictional connection through the fastening means 11. The wheel hubs 9 are mounted on the internally hollow axle tubes 7 via the hub bearings 12. The two coaxial drive shafts 3 and 4 are mounted inside the hollow axle tubes 7 via the bearings 8. In the illustrated embodiment, the motor 2 of the axle unit 1 is arranged between the two internally hollow axle tubes 7 and flanged to each of them, so that the motor 2 cannot move or rotate relative to the axle tubes 7.

[0026] The Figure 2Figure 1 shows a section of an embodiment of an axle unit 1 in the area of ​​the output sections 6 of the drive shaft 3. A characteristic feature of the illustrated embodiment is that a freewheel 14 is provided in the transmission plate 10, which is designed to act like an overrunning clutch. The transmission plate 10 is positively connected to the wheel hub 9 by means of fastening elements 11. The wheel hub 9, in turn, is supported on the internally hollow axle tube 7 via the hub bearings 12. Advantageously, the hub bearings 12 are rolling bearings which have an O-arrangement. The drive shaft 3 is supported against the axle tube 7 by the bearing 8, which is designed as a sliding bearing. Reference symbol list:

[0027] 1 - Axle unit 2 - Motor 3 - Drive shaft (left) 4 - Drive shaft (right) 5 - Inlet section 6 - Outlet section 7 - Axle tube 8 - Bearing 9 - Wheel hub 10 - Transmission plate 11 - Fastener 12 - Hub bearing 14 - Freewheel

Claims

1. Axle unit (1), in particular for trailer axles, comprising a motor (2) and two drive shafts (3, 4), wherein the drive shafts (3, 4) each have an input section (5) and an output section (6), wherein the motor (2) is designed to apply torque to the two drive shafts (3, 4) via the input sections (5), and wherein the output section (6) of each drive shaft (3, 4) is designed to drive a respective wheel directly or indirectly, characterized in that the motor (2) is arranged between the two input sections (5) of the drive shafts (3, 4), wherein at least some portions of the motor (2) are geometrically arranged between the two input sections (5) of the drive shafts (3, 4), the drive shafts (3, 4) are each one-piece, and at least one of the drive shafts (3, 4) is housed in a hollow axle tube (7).

2. Axle unit (1) according to claim 1, wherein the motor (2) is a hydraulic motor.

3. Axle unit (1) according to claim 2, wherein the motor (1) is a two-row hydraulic motor having at least two output shafts that can be decoupled from one another.

4. Axle unit (1) according to any one of claims 1 to 3, wherein a differential is arranged between the output shaft of the motor (2) and the input sections (5) of the drive shafts (3, 4).

5. Axle unit (1) according to any one of claims 1 or 4, wherein the motor (1) is an electric motor and preferably has two output shafts that can be decoupled from one another.

6. Axle unit (1) according to any one of the preceding claims, wherein the output shaft(s) of the motor (2) is / are hollow, and wherein the input sections (5) of the drive shafts (3, 4) extend, at least in some areas, into the hollow output shaft(s) of the motor (2).

7. Axle unit (1) according to any one of the preceding claims, wherein the drive shafts (3, 4) are identically constructed.

8. Axle unit (1) according to any one of the preceding claims, wherein the drive shafts (3, 4) are arranged in mirror symmetry with respect to a plane of symmetry, wherein the motor (1) intersects the plane of symmetry or is spaced a maximum of 20 cm from the plane of symmetry.

9. Axle unit (1) according to any one of the preceding claims, wherein a freewheel (14) is arranged between the output section (6) and the wheel hub (9).

10. Axle unit (1) according to any one of the preceding claims, wherein a shiftable coupling is arranged between the drive shaft (3, 4) and the wheel hub (9).

11. Axle unit (1) according to claim 10, wherein the coupling is hydraulically actuated.

12. Axle unit (1) according to claim 11, wherein the coupling is designed such that the coupling does not transmit torque in the event of a pressure drop in the hydraulic supply.