FIELD OF THE DISCLOSURE

The present disclosure relates to a bogie for a railway vehicle, to a railway vehicle comprising such a bogie and to a method for steering a bogie of a railway vehicle.

BACKGROUND OF THE DISCLOSURE

Railway vehicles, which are track bound such as trains, trams or other vehicles often exhibit wheels that are not optimally aligned to the tracks leading to higher friction between the railway track and treads of the wheels. Especially in curves with a small radius, this contact leads to an increased profile wear and noise pollution. In case of low-floor vehicles, this effect is even more pronounced: The low-floor vehicles feature smaller and less wheels per vehicle in order to increase the passenger comfort and inner space of the vehicle by having a continuous low- floor structure. However, this further leads to enhanced loads per wheel and a more pronounced fatigue of the wheel’s material causing smaller rifts or even larger material fractures.

In addition, reducing the number of wheels per vehicle and I or per bogie of the vehicle reduces the suspension comfort of the vehicle and I or of the vehicle comprising the bogie for passengers. In particular, with low floor vehicle this leads to a conflict between inner space requirements and suspension comfort requirements. Further, creating a desired suspension comfort for the passengers requires conventionally a sophisticated suspension concept arranged above the bogie and between the bogie and the vehicle, which consumes a lot of construction space and further reduces the available inner space for the passengers.

Several attempts are known to reduce the track and wheel wear. In the 1990’s, systems have been developed that were able to steer the wheels in curves. How- ever, it turned out that these solutions often suffered from undesired side effects in straight track sections such that the wheels adhered one-sided with the tread on the track, leading to an enhanced wear and noise in straight track sections. Hence, after a few years, most of these concepts were discarded and conventional concepts combined with wheel-noise absorbers and advanced industrial lubricants were again pursued.

One example of a railway bogie, which addresses these disadvantages in a successful manner is the WO2018015290 published 2018 in the name of the same applicant. The disclosed vehicle comprises a wheel assembly interconnected to a chassis as well as a method for steering said vehicle. The wheel assembly comprises a cross-member having a first end to which a first hub is interconnected by a first steering joint and a second end to which a second hub is interconnected by a second steering joint. A first wheel is attached to the first hub rotatable around a first rotation axis and a second wheel is attached to the second hub rotatable around a second rotation axis. SUMMARY OF THE DISCLOSURE

The object of the present disclosure is to provide a bogie for a railway vehicle, a railway vehicle comprising the bogie and a method for steering a bogie of a railway vehicle. In particular, it is an object of the present disclosure to provide a bogie for a railway vehicle, a railway vehicle comprising the bogie and a method for steering a bogie of a railway vehicle, which do not have at least some of the disadvantages of the prior art.

According to the present disclosure, these objects are addressed by the features of the independent claims. In addition, further advantageous embodiments follow from the dependent claims and the description.

According to the present disclosure, a bogie for a railway vehicle guided on a railway track is specified. The bogie usually comprises a base configured to be attached to or integrated in a chassis of the railway vehicle. The bogie further comprises a frame arranged rotatable with respect to the base around a vertical steering axis and two wheels each comprising a tread arranged rotatable with respect to the frame around a respective wheel rotation axis, wherein the two wheels are, in a lateral direction, arranged (essentially coaxially) spaced apart from each other. The steering axis is arranged in the lateral direction between the two wheels. The two wheels of a bogie are usually mounted rotatable and if appropriate deflectable against the force of at least one spring for suspension reasons but with respect to the other degrees of freedom fixed with respect to the bogie. In a preferred variation, the wheels are arranged essentially coaxial with respect to a common wheel rotation axis. The bogie further comprises at least one sensor assembly configured to determine during operation the lateral position of the tread of at least one of the two wheels with respect to the railway track.

The base is, in a variation of the disclosure, arranged via a bearing or a bearing assembly rotatable on the frame. One rotatable side of the bearing may be arranged on the base and the other rotatable side of the bearing or the bearing assembly may be arranged on the frame. The bearing or the bearing assembly enable the rotation between the base, connected during operation with the chassis of the railway vehicle, and the frame of the bogie.

With the steering axis being arranged in the lateral direction between the two wheels, which are arranged rotatable but with respect to each other at a quasistatic position, it is possible to steer the wheels during operation on the railway track by swiveling the frame around the steering axis. Both wheels are arranged at the frame and will simultaneously swivel as desired without the need to steer them independently.

The lateral position of the tread of at least one of the two wheels is determined during operation by the sensor assembly. The lateral position of the tread with respect to the wheel determines which area of a rolling surface of the tread is during operation in contact with the railway track. Noise pollution is usually caused by the bogies of the railway vehicle during operation in case the lateral position of the tread with respect to the wheel is not as desired. For example, a flange of the tread may contact in a narrow curve the railway track, which causes the noise pollution and increases wear. The determination of the lateral position is usually necessary to control the lateral position of the tread with respect to the railway track.

In a variation of the disclosure, each of the wheel rotation axis are arranged essentially coaxial to each other and perpendicular to the steering axis. The wheel rotation axis of the two wheels are, for example, arranged parallel to the lateral direction, in this case the wheel rotation axis are automatically also arranged parallel to each other and perpendicular to the steering axis. In a further variation of the disclosure, each of the wheel rotation axis are arranged essentially coaxially to each other. During operation, the different wheel rotation axis may be deflected independently, for example due to an independent wheel suspension, such that during operation the wheel rotation axis are not always arranged precisely coaxial. In a neutral state, without any deflection, the wheel rotation axis of both wheels are arranged coaxially with respect to each other.

It is preferable, that the at least one sensor assembly comprises with respect to a running direction of the bogie a front sensor arranged in front of the respective wheel and / or a back sensor arranged behind the respective wheel. The running direction is the direction of movement of the bogie during operation along the railway track. The movement direction of the bogie may change during operation, which means that the former front sensor becomes the back sensor and vice versa. The front sensor may be arranged in front of the respective tread and the back sensor may be arranged behind the respective tread. The sensor assembly uses, for example, the front sensor and/or the back sensor of one of the wheels and / or the front sensor and / or the back sensor of the other one of the wheels to determine during operation the lateral position of the respective tread with respect to the railway track. It is preferred that four sensors are used. Using more than one sensor increases the accuracy of the determination of the lateral position of the treads with respect to the railway track, in particular in narrow curves.

Advantageous suspension properties for the bogie are possible, when each wheel is mounted by a swing arm to the frame, wherein the swing arm is pivotable with respect to the frame around a pivot axis against the force of a swing arm spring. In other words, the swing arm is arranged pivotable to the frame around the pivot axis and the swing arm spring limits and decelerates the swing movement of the swing arm with respect to the frame. The swing arm in combination with the swing arm spring take during operation high frequency vibrations coming from the railway track.

It is preferred that the pivot axis of the swing arms is arranged parallel to the respective wheel rotation axis. It is further preferred that the pivot axis is arranged in front or behind the respective wheel rotation axis with respect to the running direction of the bogie, which creates an advantageous compact construction.

In a variation, the swing arm is fork-shaped. The fork-shape is formed by two portions, which extend mainly in the running direction, and one lateral portion, which extends mainly in lateral direction and which connects the two other portions. Preferably, one longitudinal end of the two portions is connected via the pivot axis to the frame and the other longitudinal end of the two portions is connected to the lateral portion, thereby forming the fork-shape. It is further preferred, that the lateral portion comprises a spring seat, which is configured to hold the swing arm spring. The spring seat is one contact point for the swing arm spring. The frame comprises another spring seat as second contact point for the swing arm spring.

An advantageous compact construction is achievable, when the pivot axis is arranged in front of the wheel rotation axis and the swing arm spring is arranged behind the wheel rotation axis with respect to the running direction of the bogie. In this case, the respective wheel is at least partially surrounded by the swing arm. It is further preferred for a compact and balanced construction, that the respective wheel may be mounted on the two portions of the swing arm, which extend in the running direction.

Particular good suspension results can be achieved when the swing arm spring is or comprise a rubber compound spring or a rubber metal compound spring. Rubber compound springs advantageously reduce noise pollution and undesired vibrations. The rubber metal compound spring may comprise a metal structure, which is surrounded by rubber.

In a variation of the present disclosure, the sensor assembly is at least partially arranged on the frame or the swing arm. In other words, at least some parts of the sensor assembly may be arranged on the frame or the swing arm or a combination thereof.

In a variation, the front sensor and I or the back sensor of the sensor assembly is I are interconnected to the frame or the swing arm by a sensor bracket. The sensor bracket is for example a part of the sensor assembly or a part of the frame positioning the front sensor and I or the back sensor in a predefined position, preferably in front of the tread or behind the tread. The sensor bracket provides an advantageous simple and reliable solution to hold the respective sensors in the predefined position.

In a preferred variation, the front sensor and I or the back sensor of the sensor assembly is I are during operation arranged displaceable in a vertical direction to adjust the vertical distance of the respective sensor(s) with respect to the railway track. Movement of the frame and I or movement of the swing arm may cause an undesired vertical displacement of at least one of the sensors. An undesired vertical displacement may also be caused by wheel wear, which causes a reduction of the radial extension of the wheels. Arranging the respective sensors displaceable in the vertical direction creates the possibility to compensate the undesired vertical displacement of the respective sensors.

A reliable and simple solution for adjusting the vertical distance of the front sensor and I or the back sensor of the respective sensor assembly is to provide on each sensor assembly at least one leveling actuator, which is configured to adjust during operation the vertical distance of the front sensor and I or the back sensor. In another variation, each sensor may comprise one leveling actuator configured to adjust during operation the vertical distance. In another variation, a plurality of sensors have one associated leveling actuator.

A particular advantageous solution for adjusting the vertical distance of the front sensor and I or the back sensor of the respective sensor assembly is to arrange the sensor bracket pivotable with respect to the swing arm or with respect to the frame about a leveling axis. In this variation, the sensor bracket is arranged on the swing arm or on the frame. The leveling axis is, for example, arranged parallel to the respective wheel rotation axis. In case the sensor bracket is arranged on the swing arm, the sensor bracket, comprising the respective sensors, follows the swing-movement of the swing arm with respect to the frame. Arranging the sensor bracket pivotable with respect to the swing arm creates the possibility to compensate the swing-movement of the sensor bracket and thereby holding the respective sensors in the predefined position even during swing movement of the swing arm. In a variation, at least one leveling actuator is connected to the pivotable sensor bracket and is configured to adjust the vertical position of the respective sensors during operation.

To achieve an advantageous sensing result, at least one front sensor and I or at least one back sensor is arranged on the sensor assembly such that the sensing direction is vertically oriented from the bogie to the railway track. The sensing direction is, according to this variation, parallel to the vertical direction and parallel to the steering axis. Movement, which displaces the front sensor, the back sensor and I or the sensor bracket, such that the sensing direction of the respective sensors is no longer vertically oriented, may be compensated by the at least one leveling actuator.

At least one of the front sensors and I or at least one of the back sensors may be an inductive sensor, a laser sensor, a capacitive sensor, an ultrasonic sensor, an optical sensor, a radar sensor or a combination thereof. Inductive sensors usually achieve good results, even if the railway tracks are contaminated and/or below snow. It is in particular simple to steer the frame when the bogie comprises a steering actuator, which is connected to the frame and which is configured to swivel the frame during operation about the steering axis, by a steering angle, with respect to the base. The steering actuator is, for example connected to the base and the frame, which enables swiveling of the frame with respect to the base. In another variation, the steering actuator may be connected directly to the chassis of the railway vehicle.

In order to control the movement of the bogie, the bogie may comprise per wheel an electrical engine, which is configured to drive during operation the corresponding wheel. The electrical engine is, for example, arranged coaxially with respect to the wheel and may be arranged on the same shaft as the wheel. The electrical engine may be arranged on the outer lateral side of the wheel to realize a particular compact construction. It is preferred that the electrical engine is an in-hub traction motor. Further, driving during operation comprises to accelerate the respective wheel via the electrical engine or to decelerate the respective wheel. The electrical engine may therefore function as a motor brake for braking of the respective wheel. It is for example preferred that the motor brake is the main brake of the railway bogie. It is also conceivable that one of the electrical motors is controlled to accelerate and the other electrical motor of the bogie, arranged on the opposite side of the bogie is controlled to decelerate (or to accelerate slowly) for steering of the railway bogie around the steering axis, which may be in particular silent. The electrical engine may further be used for regenerative braking for energy recovery, stored in respective batteries. It is further preferred that the electrical engines are the only brakes of the railway bogie configured for decelerating of the railway bogie during operation of the railway bogie. In this embodiment, the railway bogie does not comprise standard mechanical brakes, for example disc brakes etc.. This brakeless embodiment provides a simple braking solution for the railway bogie. The railway bogie of this variation may further comprise capacitor banks, which provide electrical energy to the electrical engines for braking in case the standard electrical system of the railway bogie or the railway vehicle fails. Further, the bogie may comprise a brake, which is configured to decelerate during operation the corresponding wheel. The brake is for example a disk brake, preferably an internally ventilated disk brake, wherein the disk of the disk brake is, for example, arranged coaxially with respect to the wheel and may be arranged on the same shaft as the wheel. The disk of the disk brake may be arranged on the outer lateral side of the electrical engine to realize a particular compact construction.

To achieve an advantageous compact construction, a brake caliper of the disk brake may be fixedly arranged on the swing arm, preferred on one of the two in running direction-extending portions of the swing arm.

An advantageous simple and reliable steering of the bogie is achievable, when the bogie further comprises a control unit, configured to receive during operation the measured lateral position, and configured to determine a steering angle, based on the received lateral position. The control unit is further configured to control the steering actuator based on the determined steering angle. The control unit is further, additionally or alternatively, configured to control the at least one electrical engine and / or the at least one brake, based on the determined steering angle, for swiveling the frame around the steering axis with respect to the base. The desired steering of the bogie is according to this variation achieved by controlling the steering actuator and I or by controlling the electrical engines and brakes of the wheels. The electrical engines of the wheels and the brakes may be controlled during operation in such a way that the steering of the bogie is achieved. For example, one wheel decelerates and the other accelerates which causes swiveling of the bogie with respect to the base. The control unit may be arranged on or in the bogie. In another variation, the control unit is arranged outside of the bogie, for example, in the railway vehicle.

A steering system of the bogie may be the steering actuator, the electrical engines and the brakes and I or the steering actuator in combination with the electrical engine and the brakes.

In a variation of the disclosure, the frame comprises a base frame and a wheel frame interconnected via a spring damping system with each other, wherein the base is arranged on the base frame, and wherein the wheels are arranged on the wheel frame. It is preferred that the swing arm is arranged on the wheel frame, interconnecting the wheels with the wheel frame. Having the base frame and the wheel frame interconnected via the spring damping system creates the possibility to dampen vibrations and movements coming, during operation, from the chassis of the railway vehicle and to dampen additionally vibrations coming from the railway track. This variation of the disclosure increases advantageously the suspension comfort during operation of the bogie. In a variation, the spring damping system comprises a plurality of dampers and a plurality of spring assemblies, each spring assembly comprises a first spring and a second spring arranged coaxially to each other. The spring assemblies are arranged preferably in corner portions of the frame. The first spring and the second spring have different spring properties, which increases the range of frequencies, which can be absorbed during operation by the spring damping system, compared to a single spring. The spring assemblies are preferably arranged essentially vertically between the base frame and the wheel frame. At least some of the dampers may be arranged next to or in the area of the spring assemblies for an advantageous suspension comfort.

In a variation of the disclosure, the plurality of dampers comprises first dampers, which are arranged substantially vertically, and second dampers, which are arranged substantially horizontally. In other words, the longitudinal axis of the first dampers is arranged parallel to the vertical direction and the longitudinal axis of the second dampers is arranged substantially in the lateral direction. The first dampers are configured to absorb, during operation, vertical vibrations and the second dampers are configured to absorb, during operation, lateral I horizontal vibrations. This variation achieves the advantageous suspension comfort with respect to vertical and lateral vibrations during operation of the bogie.

It is preferred for a compact construction, which increases the available inner space in the railway vehicle, when the base frame is arranged parallel to wheel frame. In particular, the main extension plane of the base frame is arranged parallel to the main extension plane of the wheel frame. The main extension planes are preferably arranged perpendicular to the steering axis. The main extension planes are imaginary planes, which extend along the two main extension directions of the base frame and the wheel frame. In mounted position, the main extension planes of the base frame and the wheel frame extend, according to this variation, in the lateral and in the running direction. The compact construction advantageously allows damped movement in certain directions and is stiff in other directions.

A particular compact construction is achievable when the maximal vertical extension of the wheels exceeds the maximum vertical extension of the base frame. In other words, the base frame is arranged vertically within the vertical extension of the wheels.

In a variation of the disclosure, the base frame is arranged above an imaginary separating plane, which is arranged perpendicular to the steering axis and which intersects a center of the first wheel and I or the second wheel. In case the wheel rotation axis are arranged parallel, the imaginary separating plane extends along the wheel rotation axis. It is further preferred that the wheel frame is mainly below the imaginary plane. In other words, the base frame is arranged vertically above the wheel rotation axis and the wheel frame is mainly, with the majority of its volume, arranged vertically below the wheel rotation axis. This construction enables an advantageous compact design, which increases the available inner space within the railway vehicle.

It is preferred for a compact construction, when the two wheels are at least partially surrounded by the frame, in particular by the base frame and / or by the wheel frame. For example, the base frame and I or the wheel frame extend in the running direction and / or in the lateral direction beyond the wheels.

It is preferred for a particular compact construction, when the base frame is arranged mainly, with the majority of its volume, within an imaginary box, which is defined by the outer edges of the wheel frame.

In a variation of the present disclosure, the frame further comprises a plurality of struts, preferably four struts, which connect the base frame with the wheel frame, wherein the longitudinal axis of the struts is arranged perpendicular to the steering axis. The struts are preferably connected such to the base frame and to the wheel frame that vertical movement between the base frame and the wheel frame is enabled and that further movement, in particular lateral movement and movement in running direction, is inhibited. In other words, the struts allow vertical freedom between the base frame and the wheel frame and create stiffness in the other directions. The steering torque I movement from, for example, the steering actuator, can therefore be transferred via the struts advantageously from the base frame to the wheels. In order to achieve the desired stiffness, the struts may be arranged parallel to each other and parallel to the running direction of the bogie.

In a further variation, the frame and I or other components of the bogie is or are made of or comprise at least partially a lightweight material. Lightweight material may comprise aluminum, an aluminum alloy, lightweight steel alloy, a composite material, a fiber reinforced composite material or a combination of the aforemen- tioned materials. A lightweight structure of the bogie helps to reduce energy consumption during operation of the railway bogie and improves the overall environmental footprint.

In a preferred variation, the frame and I or other components of the bogie has or have a lightweight design shape. The lightweight design shape of parts is a shape, which has a reduced weight due to a specific design, without losing its required functionality. The lightweight design shape comprises for example slim I thin structures, which follow its respective function compared to a standard design, which is for example constructed by standard parts like, bars, rods or standard profiles. Further, the lightweight design shape is for example determined using simulation results of the different parts of the railway bogie such that material is added where it is needed and removed where it is not needed.

In an aspect of the present disclosure a railway vehicle is specified, which comprises a bogie as described above and hereinafter.

In a further aspect of the present disclosure, a method for steering a bogie of a railway vehicle is specified. The method comprising the following steps: providing a railway vehicle comprising the bogie as described above and hereinafter; determining, by the at least one sensor assembly, the lateral position of the tread of at least one of the two wheels with respect to the railway track; receiving, in a control unit, the determined lateral position and calculating a steering angle, using the received lateral position; swiveling, by a steering system, the bogie around the steering axis about the calculated steering angle, for steering the bogie with respect to the base. The steering system may comprise the steering actuator and I or at least one electrical engine and I or at least one brake.

It is to be understood that both the foregoing general description and the following detailed description present embodiments, and are intended to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings are included to provide a further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments, and together with the description serve to explain the principles and operation of the concepts disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The herein described disclosure will be more fully understood from the detailed description given herein below and the accompanying drawings, which should not be considered limiting to the disclosure described in the appended claims. The drawings are showing:

Fig. 1 a perspective view of a first variation of the bogie according to the disclosure; Fig. 2 a first perspective view of a second variation of the bogie according to the disclosure;

Fig. 3 a second perspective view of the second variation of Fig. 2;

Fig. 4 a detailed view of Fig. 3;

Fig. 5 a top view of the second variation of Fig. 2;

Fig. 6 a first sectional view of the second variation of Fig. 5 indicated by section line I;

Fig. 7 a second sectional view of the second variation of Fig. 5 indicated by section line J;

Fig. 8 a first perspective view of a variation of a wheel of the bogie;

Fig. 9 a second perspective view of the variation of the wheel of the bogie;

Fig. 10 a perspective view of a variation of a swing arm of the bogie;

Fig. 11 a perspective view of a variation of a base frame of the bogie;

Fig. 12 a perspective view of a variation of a wheel frame of the bogie;

Fig. 13 a perspective view of a connecting part of the bogie. DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

Figure 1 shows a perspective view of a first variation of the bogie according to the disclosure. Figure 2 shows a first perspective view of a second variation of the bogie according to the disclosure. Figure 3 shows a second perspective view of the second variation of Figure 2. Figure 4 shows a detailed view of Figure 3. Figure 5 shows a top view of the second variation of Figure 2. Figure 6 shows a first sectional view of the second variation of Figure 5 indicated by section line I. Figure 7 shows a second sectional view of the second variation of Figure 5 indicated by section line J. Figure 8 shows a first perspective view of a variation of a wheel of the bogie. Figure 9 shows a second perspective view of the variation of the wheel of the bogie. Figure 10 shows a perspective view of a variation of a swing arm of the bogie. Figure 11 shows a perspective view of a variation of a base frame of the bogie. Figure 12 shows a perspective view of a variation of a wheel frame of the bogie. Figure 13 shows a perspective view of a connecting part of the bogie.

As e.g. visible in Figures 1, 2, 3 and 5, a bogie 1 comprises a base 2, which is configured to be attached to a chassis of a railway vehicle. The base 2 may be connected to a connecting part 9, which is configured to be connected to the chassis of the railway vehicle during operation of the bogie 1 . The bogie 1 further comprises a frame 3 arranged rotatable with respect to the base 2 around a vertical steering axis 4. The bogie 1 further comprises two wheels 5, which comprise a tread 6. The tread 6 or tread profile is the radially external portion of the wheel 5. The tread 6 comprises a contact surface or a rolling surface, which is, during operation, in contact with the railway track. The wheels 5 are arranged rotatable with respect to the frame 3 around a respective wheel rotation axis 7. The wheel rotation axis 7 of the wheels 5 are arranged essentially coaxially to each other and the steering axis 4 is arranged in a lateral direction Y between the two wheels 5. In another variation, the wheel rotation axis 7 may be arranged at a specific angle with respect to the lateral direction Y. In this case, the wheel rotation axis 7 are inclined with respect to the lateral direction Y. Figure 1 further shows covers 30 arranged on the frame 3 for protection of the bogie 1 during operation.

The bogie 1 further comprises a sensor assembly 11 , best visible in Figures 3, 4 and 7, which is configured to determine during operation the lateral position of the tread 6 of the two wheels 5 with respect to the railway track. The sensor assembly 11 enables to determine the position of the treads 6 of the wheels 5 on the railway track during operation, which is crucial to control the position of the treads 6 of the wheels 5 with respect to the railway track for noise and wear control.

Figure 1 further shows a steering actuator 16, which is connected to the frame 3 and to the connecting part 9. The connecting part 9 is also shown in Figure 13. Movement of the steering actuator 16 cause a rotation of the frame 3 around the steering axis 4 by a steering angle with respect to the base 2 and with respect to the connecting part 9 and also with respect to the chassis of the railway vehicle.

The Figures 2, 3, 5, 7 and 8 to 10 further show a swing arm 20. Each of the wheels 5 is pivotable mounted by the swing arm 20 to the frame 3. The swing arm 20 is arranged pivotable with respect to the frame 3 around a pivot axis 21 against the force of a swing arm spring 22, best visible in Figures 6 and 8. The pivot axis 21 is arranged parallel with respect to the wheel rotation axis 9. A bearing point of the wheel 5 is arranged on the swing arm 20 between the pivot axis 21 and the swing arm spring 22. In other words, the wheels 5 are, according to the embodiment as shown in the Figures, mounted on the swing arm 20 between the pivot axis 21 and the swing arm spring 22.

Figures 3, 4 and 7 further show the sensor assembly 11 in detail. The sensor assembly 11 comprises a front sensor 13 arranged in front of the respective tread 6 of the wheel 5 with respect to a running direction X of the bogie 1 . The sensor assembly 11 further comprises a back sensor 14 arranged behind the respective tread 6 of the wheel 5 with respect to the running direction X of the bogie 1 . As best visible in Figure 3, both wheels 5 of the bogie 1 comprise the front sensor 13 and the back sensor 14. The front sensors 13 and the back sensors 14 are arranged on a sensor bracket 15, which is mounted pivotable on the swing arm 20. The sensor bracket 15 extends along the wheel 5 and holds the respective sensors 13, 14 at a predefined position during operation of the bogie 1 . The sensor bracket 15 is arranged pivotable with respect to the swing arm 20 around a leveling axis 10, best visible in Figures 4 and 7. The leveling axis 10 is arranged parallel with respect to the respective wheel rotation axis 4 and parallel with respect to the pivot axis 21 .

The bogie 1 further comprises leveling actuators 8, best visible in Figures 6 and 11 , which are connected to the frame 3 and to the respective sensor bracket 15. Linear movement of the leveling actuators 8 adjusts during operation of the bogie 1 the vertical distance of the front sensor 13 and I or of the back sensor 14 with respect to the railway track. Movement of the swing arm 20, which might change the vertical distance of at least one of the sensors 13, 14, can be compensated by movement of the leveling actuators 8. In the variation of the disclosure as shown in the Figures, the linear movement of the leveling actuators 8 causes pivoting of the connected sensor bracket 15 around the leveling axis 10. The pivoting around the leveling axis 10 compensates a possible deflection of the swing arm 20 against the swing arm spring 22 during operation of the bogie 1 , such that the vertical position of the respective sensors 13, 14 may stay as static as possible. In another variation, the leveling actuators 8 associated with the respective sensors 13, 14 may move independently, such that each of the sensors 13, 14 is always at the predefined vertical position.

The Figures 1 to 9 further show that each wheel 5 comprises an electrical engine 18 and a brake 19. The electrical engine 18 is configured to drive, if required, during operation the respective wheel 5, and the brake 19 is configured to decelerate, if required, during operation of the bogie 1 the respective wheel 5. The brake 19 is a disk brake and the disk of the disk brake is arranged on the same shaft as the respective wheel 5 and the respective electrical engine 18. The wheel 5, the electrical engine 18 and the disk are partially surrounded and held by the swing arm 20, best visible in Figures 8 and 9. A brake caliper of the brake 19 is arranged on the swing arm 20.

The Figures further indicate schematically a control unit 17. The control unit 17 is, for example arranged within the bogie 1 or at a different position of the railway vehicle. The control unit 17 is configured to receive, during operation of the bogie 1 , the measured lateral position of the respective sensor(s) 13, 14 and is further configured to determine the steering angle based on the received lateral position. The control unit 17 is further configured to control the steering actuator 16 and I or to control the electrical engines 18 and the brakes 19 based on the determined steering angle for swiveling the frame 3 around the steering axis 4 with respect to the base 2.

In particular, the Figures 1, 2, 3, 6, 11 or 12 show that the frame 3 comprises a base frame 23 and a wheel frame 24. The Figure 11 shows the base frame 23 in detail and the Figure 12 shows the wheel frame 24 in detail. The base frame 23 is arranged mainly above the wheel frame 24. The base frame 23 is interconnected to the wheel frame 24 via a spring damping system 12 and vice versa. The base 2 of the bogie 1 is arranged on the base frame 23 and the two wheels 5 are arranged on the wheel frame 24, via the swing arm 20. The spring damping system 12 comprises a plurality of dampers 25, which are configured to dampen different kind of movement I vibrations of the bogie 1 during operation. According to the variation of the disclosure as shown in the Figures, four of the dampers 25 are arranged vertically. In other words, the longitudinal axis of the four dampers 25 are arranged parallel to a vertical direction Z, these dampers 25 are configured to dampen vertical vibrations. Further, two of the dampers 25 are arranged mainly in the lateral direction Y, best visible in Figure 5. These dampers 25 are configured to dampen lateral vibrations I movement. The spring damping system 12 further comprises four spring assemblies 26. The spring assemblies 26 comprise a first spring 27 and a second spring 28. The first spring 27 is arranged coaxially with respect to the second spring 28. The second spring 28 has a smaller radial extension than the first spring 27 and is arranged within the first spring 27. Both springs 27, 28 engage with the base frame 23 and the wheel frame 24 and are configured to absorb in combination with the dampers 25 during operation of the bogie 1 vibrations resulting from movement of the bogie 1 on the railway track.

The swing arm 20 is mounted pivotable on the wheel frame 24 against the force of the swing arm spring 22. Figure 12 shows the attachment point of the pivot axis 21 of the respective swing arms 20 on the wheel frame 24. The Figures 10 and 12 further show a spring seat 32 on the swing arm 20 and a spring seat 33 on the wheel frame 24 for the swing arm spring 22. The swing arm spring 22 engages with the swing arm 20 and with the wheel frame 24 via the spring seats 32, 33.

The Figures further shows stops 31 , best visible in Figures 2 and 12, arranged on the base frame 23, wherein some of the stops 31 limit the movement of the base frame 23 with respect to the wheel frame 24. The other stops 31 limit the maximal possible swiveling of the frame 3 with respect to the base 2.

The Figures 1 to 5 and in particular the Figures 6 and 7 show the compact construction of the bogie 1 . This is the result of the compact and interlaced design of the different parts of the bogie 1. The wheels 5 are in combination with the electrical engine 18 and the brake 19 partially surrounded and held by the swing arm 20. The wheel frame 24 surrounds partially the swing arm 20 and the majority of the wheel frame 24 is arranged below the wheel rotation axis 7. The majority of the base frame 23 is arranged above the wheel rotation axis 7 and does not extend beyond the maximal radial extension of the wheels 5 with respect to the vertical direction Z. The maximal vertical extension of the wheel frame 24 does also not extend more than ten millimeters, preferably fife millimeters, above the maximal radial extension of the wheels 5 with respect to the vertical direction Z, which increases available inner space within a railway vehicle using the bogie 1 , see Figures 6 and 7.

The Figures 1, 2, 5 and 6 further show four struts 29, which connect the base frame 23 with the wheel frame 24. The longitudinal axis of the struts 29 is arranged parallel to each other and is further arranged parallel with the running direction X in a resting state of the bogie 1 . The struts 29 are connected such with the base frame 23 and the wheel frame 24 that vertical movement between these two parts is, within certain limits, enabled (damped by the spring damping assembly 12) and that movement in the running direction X is inhibited. Movement of the steering actuator 16 results therefore in the desired direct and precise steering of the wheels 5, which is in particular advantageous in narrow curves.

Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the Spirit and scope of the disclosure. LIST OF DESIGNATIONS

1 Bogie 20 Swing arm

2 Base 21 pivot axis

3 Frame 22 Swing arm spring

4 Steering axis 23 Base frame

5 Wheel 24 Wheel Frame

6 Tread 25 Damper

7 Wheel rotation axis 26 Spring assembly

8 Leveling actuator 27 First spring

9 Connecting part 28 Second Spring

10 Leveling axis 29 Strut

11 Sensor assembly 30 Cover

12 Spring damping system 31 Stop

13 Front sensor 32 Spring seat on swing arm

14 Back sensor 33 Spring seat on wheel

15 Sensor bracket frame

16 Steering actuator X running direction

17 Control unit Y lateral direction

18 Electrical engine Z vertical direction

19 Brake