GB2603201A

GB2603201A - Bogie for a light rail system

Info

Publication number: GB2603201A
Application number: GB2101415.4A
Authority: GB
Inventors: Pemberton Martin; Salkeld Paul; Hall Matthew; Gustafsson Jorgen; Howson Adrian; Sozanski Antoni
Original assignee: Coventry City Council
Current assignee: Coventry City Council
Priority date: 2021-02-02
Filing date: 2021-02-02
Publication date: 2022-08-03
Also published as: GB202101415D0

Abstract

A bogie 100 for a rail-based vehicle, such as a train or tram. The bogie comprises one or more rail wheel arrangements 110, 120, each having two train rail wheels 111, 112. An open differential 115 connects the train wheels together which allows the first and second wheels to be driven simultaneously but so that the first rail wheel is able to rotate at a different speed to the second rail wheel. The differential may or may not be a locking or limited slip differential. Each wheel arrangement may comprise a separate motor. The wheel arrangements may comprise a single mount for coupling both the motor and open differential to the bogie. A rail-based vehicle comprising such a bogie is also claimed. The rail vehicle may further comprise a battery to provide power to the motors. The rail vehicle may further comprise an inverter to convert DC voltage from the battery to an AC voltage to power the motor.

Description

BOGIE FOR A LIGHT RAIL SYSTEM

FIELD OF THE INVENTION

The present invention relates to the field of rail-based vehicles, and in particular, to bogies for use with rail-based vehicles.

BACKGROUND OF THE INVENTION

There is a long tradition of rail-based vehicles, such as trams or trains, that propel themselves along rail-based infrastructure, e.g. along one or more tracks coupled to a ground surface.

One problem facing rail-based vehicles is the difficulty in going around a corner. In particular, a pair of rail wheels (each coupled to a separate, parallel rail) are usually connected via a single fixed axle so that they turn at a same speed. However, during cornering, one rail wheel will travel a shorter distance than the other rail wheel. This causes some conflict as, if the rail wheels are of same size, then slippage and/or friction/grinding can occur due to the different distances that the rail wheels need to travel.

The usual solution to this issue is to use rail wheels that have a diameter that reduces in a direction going from inside the rails to outside the rails (i.e. towards an outside of the tracks). This results in, as the rail-based vehicle moves around a corner, the effective diameter of each the pair of rail wheels changing, so that they can rotate at a same speed whilst covering different distances.

However, this approach still imparts a restriction on the maximum turning radius of the rail-based vehicle, as there is a limit to the safe extent to which the effective diameter of the wheel can change (e.g. due to manufacturing constraints or risk of derailment). There is an ongoing desire to improve the operation of rail-based vehicles.

SUMMARY OF THE INVENTION

The invention is defined by the claims According to examples in accordance with an aspect of the invention, there is provided a bogie for a rail-based vehicle, the bogie comprising one or more rail wheel arrangements. Each rail wheel arrangement comprises: a first rail wheel a second, different rail wheel and an open differential connecting the first and second rail wheels together, so that the first and second rail wheels are driven simultaneously, but so that the first rail wheel is able to rotate at a different speed to the second rail wheel.

The present invention proposes the use of an open differential in a bogie for a rail-based vehicle. It is an underlying recognition of the present invention that some rail-based vehicles, and in particular rail-based vehicles for use in an urban environment, would benefit from a capability of travelling around relative tight corners, e.g. to negotiate a corner having a radius of no more than 25m, e.g. no more than 15m. It is also herein recognized that, in such environments, the weight of the rail-based vehicle is usually relatively low, meaning that it is no longer essential for wheels to be connected together by a fixed axle (which, for standard rail-based vehicles, is essential to allow the bogie to provide sufficient structural support for the rail-based-vehicle).

Thus, the present disclosure relies upon the recognition that a problem of how to provide sharp corners for a rail-based vehicle, e.g. for an urban environment, arises at a same time as a weight of the rail-based vehicle reduces (i.e. as lighter rail-based vehicles are used in the same circumstances). This facilitates the use of an open differential in a bogie for the rail-based vehicle. Previously, open differentials were not usable, as fixed-axle structures were considered essential to provide suitable support (i.e. without breaking) for a rail-based vehicle.

The present invention therefore recognizes a particular use case in which a rail-based vehicle having an open differential would be advantageous and possible, e.g. without breakage or having unreliable structural integrity.

An alternative label for a bogie is a "truck' and the terms are considered interchangeable.

Preferably, the one or more rail wheel arrangements comprises two or more rail wheel arrangements. Of course, the bogie may comprise any number of rail wheel arrangements, but embodiments are particularly preferably when there are a plurality of rail wheel arrangements.

In preferred examples, the open differential of each rail wheel arrangement is an open differential configured for use with a motor vehicle, such as a car. The present invention advantageously recognizes that, for some rail-based vehicles, an open differential designed for a motor vehicle such as a car can be repurposed for use in the rail-based vehicle. This embodiment thereby makes use of "off-the-shelf' components, reducing a cost of providing a bogie according to an embodiment, as well as being able to make use of components that have been tested for reliability and dependability.

Preferably, the bogie is configured to support a rail-based vehicle having a weight no greater than 20,000kg, e.g. no greater than 17,000kg, e.g. no greater than 12,000kg (e.g. if excluding passenger weights). Thus, the weight (of the vehicle) may range from 10,000kg to 20,000kg, from 10,000kg to 17,000kg, from 10,000kg to 12,000kg. In particular, the use of an open differential in the bogie is particularly advantageously used in an urban environment, in which the weight of the rail-based vehicle is generally lower. This embodiment recognizes the particularly advantageous use-case scenario for the open differential, and recognizes that the use of an open differential may affect the total amount of weight that the bogie can support.

Preferably, the open differential of each rail wheel arrangement does not comprise a limited slip differential or a locking differential. Use of a limited slip differential or a locking differential can increase the chance that the rail-based vehicle will derail. By excluding these options from the bogie, this risk of derailment can be reduced.

Optionally, each rail wheel arrangement further comprises a wheel framework, comprising one or more lateral beams connected between the first and second rail wheel. This embodiment will improve the structural integrity of the bogie. For instance, the lateral beams can provide additional structural support to account for the reduction in structural support that results from not using a fixed axle.

In some examples, each rail wheel arrangement comprises a different motor configured to drive the first and second rail wheel, of the rail wheel arrangement, using the open differential. This approach facilitates improved control over the torque applied to each wheel arrangement, e.g. to allow different amounts of torque to be applied at different points around a corner or up/down an incline. This approach can improve the efficiency of the rail-based vehicle.

Each rail wheel arrangement may comprise a gearbox connected between the motor of the rail wheel arrangement and the open differential of the rail wheel arrangement. Use of a gearbox can allow tailoring or customizing of the wheel speed of the rail wheel arrangement to suit the electrical motor selected. In other words, a gearbox can be used to allow the electrical motor to operate at the most efficient RPM (e.g. most energy efficient), whilst providing a different RPM for the open differential.

In some embodiments, the motor, of each rail wheel arrangement, is mounted together with the open differential of the rail wheel arrangement. In particular, each rail wheel arrangement may comprise a single mount for coupling both the open differential and the motor, of the rail wheel arrangement, to the remainder of the bogie. For instance, the open differential and the motor may be provided in a same housing -i.e. form a single unit. In particular examples, coupling of the motor and the open differential may be via a resilient drive and via a drive/Cordon shaft.

The motor of each rail wheel arrangement is configured to operate at a rotation speed of up to 8000 rotations per minute. Other suitable rotation speeds will be apparent to the skilled person In some examples, the motor of each rail wheel arrangement is configured to provide a torque of up to 150Nm.

Preferably, the motor of each rail wheel arrangement is an electric motor. In some examples, the electric motor of each rail wheel arrangement is configured to receive power from an inverter, wherein motors of different rail wheel arrangements receive power from different inverters.

There is also proposed a rail-based vehicle comprising two or more bogies as herein described.

In particular, there may be provided a rail-based vehicle comprising: two or more bogies, which each rail wheel arrangement comprises an electric motor; and a battery configured to provide power to the motor of each rail wheel arrangement.

Preferably, the rail-based vehicle further comprises, for rail wheel arrangement, a separate inverter for converting a DC voltage, provided by the battery, to an AC voltage for powering the motor of said rail wheel arrangement.

In some examples, the overall weight of the rail-based vehicle is less than 20,000kg, e.g. less than 17,000kg, e.g. less than 12,000kg (e.g. if excluding passenger weight). Preferably, the overall weight of the rail-based vehicle is no less than 10,000kg (e.g. excluding passengers). Thus, the weight may range from 10,000kg to 20,000kg, from 10,000kg to 17,000kg, from 10,000kg to 12,000kg.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: Figures 1 and 2 illustrate a bogie according to an embodiment; and Figure 3 illustrates a rail-based vehicle according to an embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described with reference to the Figures.

It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

The invention provides a bogie for a rail-based vehicle, such as a train or tram. The bogie comprises one or more rail wheel arrangements, each having two train rail wheels. An open differential connects the train wheels together, so that each wheel is able to turn at a different speed to the other wheel, whilst being driven by a same motor.

The inventors have recognized that, in certain use-case scenarios, it is possible to use an open differential, and specifically those designed for use with automotive vehicles, for a rail-based vehicle. By allowing the rail wheel to rotate at different speeds, a rail-based vehicle is able to improve a cornering efficacy (e.g. avoiding friction and/or slipping of the rail wheels -which can lead to derailment), and reduce a maximum (safe) turning radius for the rail-based vehicle.

Effectively, the present invention recognizes a benefit in using an open differential in a rail-based vehicle.

Figures 1 and 2 illustrates a bogie 100 according to an embodiment of the invention. The bogie is designed for a rail-based vehicle, e.g. a carriage, train or tram. The rail-based vehicle may comprise a plurality of such bogies, as would be readily apparent to the skilled person.

Figure 1 provides a perspective view of the bogie 100, and Figure 2 provides a top-down view of the bogie 100.

The bogie 100 comprises a first rail wheel arrangement 110 and a second rail wheel arrangement 120. The skilled person would appreciate that the bogie may be adapted to comprise only a single rail wheel arrangement or more than two rail wheel arrangements. The first 110 and second 120 rail wheel arrangements are near-identical, differing primarily in their positions on the bogie. For the sake of conciseness, only a single C) one of these rail wheel arrangements will be hereafter described, although the other rail wheel arrangement may comprise similar/corresponding elements.

The first rail wheel arrangement 110 comprises a first rail wheel 111 and a second rail wheel 112. A rail wheel is a wheel that is configured/designed for use on a railway track. The first and second rail wheels are connected/coupled together via an open differential of the first rail wheel arrangement. Thus, the first and second rail wheels are driven at a same time, e.g. using a same transmission axle, but are able to rotate at different speeds. The operation of an open differential will be known to the person familiar with mechanical systems.

In particular, the first rail wheel 111 connects to the open differential via a first rail wheel axle 113, and the second rail wheel connects to the open differential via a second rail wheel axle 114. The skilled person will appreciate how the open differential allows each rail wheel axle to rotate at different speeds, whilst being driven simultaneously by a same transmission axle (not shown) provided to the open differential.

The open differential may function in the same way a conventional open differential operates. An input pinion (e.g. connected to the transmission axle) to the differential turns a ring gear and a cage, upon which a planet gear is mounted. The planet gear is in turn connected so as to rotate two sun gears, each of which is coupled to a respective rail wheel axle. In particular, the planet gear is positioned able to rotate about an axis of the ring gear as well as spin about its own axis. Rotation of the planet gear about the axis of the ring gear induces a same rotation to both sun gears. Rotation of the planet gear about its own axis induces opposite rotations in both sun gears.

Generally, when the bogie 100 is travelling down a straight track, all rail wheels can be assumed to spin at the same speed. Effectively, this means that the planet gear does not rotate about its own axis, so that both wheel axles are rotated at a same speed.

However, as the bogie begins to turn, the wheels wish to turn at different speeds.

This causes the planet gear to begin spinning about its axis, allowing the wheels to move at different speeds. This happens automatically (i.e. without being controlled by a computer/user). In preferred embodiments, the open differential of each rail wheel arrangement does not comprise a limited slip differential or a locking differential. There is an increased risk of derailment if such differentials are used (e.g, if the differential fails to unlock), meaning that an improved safety can be ensured if the open differential does not comprise a limited slip or a locking differential.

Each open differential may be driven by a respective (electrical) motor. Thus, each wheel arrangement may comprise a respective motor for powering the rail wheels. The (electrical) motor of each wheel arrangement may be powered by a battery on-board the rail-based vehicle (e.g. mounted separately to the bogie itself).

The battery may be connected to a power distribution unit which distributes electrical power to an inverter. One inverter may be provided per motor. Accordingly, the electric motor of each rail wheel arrangement may be configured to receive power from an inverter, wherein motors of different rail wheel arrangements receive power from different inverters An inverter converts DC power (provided by a battery or cell arrangement) to an AC power, e.g. for driving an electric motor. The operation of an inverter is well known to the skilled person.

The (electric) motor may be mounted to a same framework and/or mount as the open differential. That is, the open differential and the motor may be connected to the remainder of the bogie by a same mount.

Preferably, the motor of each rail wheel arrangement is configured to operate at a rotation speed of up to no more than 8000 rotations per minute (e.g. up to no more than 6000 RPM) and/or configured to provide a torque of up to no more than 150Nm (e.g. up to no more than 145Nm).

In preferred examples, the motor is coupled to the open differential by one or more gearboxes. This allows a motor to operate according to an "optimal" rotation speed, e.g. most efficient rotation, whilst still powering the open differential at a desired rotation. The one or more gearboxes may, for instance, be gearboxes designed for an automotive vehicle.

The first rail wheel arrangement 110 may further comprise a first framework 118. The first framework is configured to support the rail wheel axles 113, 114 of the first rail wheel arrangement 110. The first framework 118 acts to improve the structural integrity of the 25 bogie.

In particular, it is recognized that the use of an open differential 115 means a reduction in the overall strength/stiffness of the bogie. In existing bogie designs, the single wheel axle provides strength to the bogie, which is lost if an open differential 115 is used -as the single wheel axle will be effectively split into the first rail wheel axle 113 and the second rail wheel axle 114.

The use of the first framework 118 provides additional structural strength to account for this lost structural integrity, thereby overcoming a problem of lost strength without losing the advantages of an open differential (for improved cornering capabilities). In particular, the first framework can help reduce the impact of lateral forces (e.g. centripetal forces introduced during turning) and/or twisting of the bogie due to uneven weight distribution, movement over uneven surfaces or the like, The first framework 118 may be connected to the first and second rail wheel axles by respective bearings 119 (of which only one is visible in Figure 1). This allows the rail wheel axles (and therefore respective rail wheels) to freely rotate, whilst still providing additional support.

The first framework 118 may be formed of one or more lateral beams 118A, which are connected to the first and second rail wheel axles (and therefore the first and second rail wheels) via respective bearings. In particular, the one or more lateral beams may be connected at either end by respective framework plates 118B, which each mount a respective bearing for the first/second rain wheel axle.

In the illustrated embodiment, the first framework 118 comprises four lateral beams 118A, but any number of lateral beams 118A can be used.

If there is more than one lateral beam, then the lateral beams may be further braced together by one or more bracing members 118C. This acts to further increase the structural support provided by the first framework.

Preferably, the open differential 115 is an open differential designed for an automotive vehicle (such as a car). These open differentials are usually compact (i.e. reducing a size of the overall bogie) and can be provided "off-the-shelf', thereby reducing the cost and design complexity of the overall bogie.

The use of an open differential designed for an automotive vehicle is particularly advantageous if the first rail wheel arrangement comprises the first framework 118, as it provides additional space and/or flexibility for positioning the one or more lateral beams.

The bogie 100 also comprises a bogie frame 150, sometimes called a chassis or a framework, configured or arranged to be fastened to a carriage, train or tram (not shown), i.e. the rest of the rail-based vehicle. The bogie frame 150 may connect to the carriage via a fastening mechanism 155. The fastening mechanism 155 may be configured to rotate with respect to a connected carriage, e.g. the fastening mechanism may allow the bogie 100 to rotate about some predetermined axis. Thus, the fastening mechanism 155 may comprise a fulcrum.

However, this is not essential, and the bogie may instead be fixedly secured to the remainder of the rail-based vehicle.

If present, the first framework 118 may form part of this bogie frame 150.

Figure 3 illustrates a rail-based vehicle 300 according to an embodiment. The rail based vehicle comprises a plurality of bogies 100, and in the illustrated example, comprises only two bogies.

The rail-based vehicle may further comprise a battery 310. The battery may be configured to provide power to the motor of each rail wheel arrangement (of the bogies 100), e.g. if the motors are electric motors.

In preferred examples, the rail-based vehicle further comprises, for each rail wheel arrangement, a separate inverter for converting a DC voltage, provided by the battery, to an AC voltage for powering the motor of said rail wheel arrangement.

Preferably, the overall weight of the rail-based vehicle is less than 20,000kg, e.g. less than 17,000kg, e.g. less than 12,000kg (e.g. if excluding passenger weight). Preferably, the overall weight of the rail-based vehicle is no less than 10,000kg (e.g. excluding passengers). Thus, the weight may range from 10,000kg to 20,000kg, from 10,000kg to 17,000kg, from 10,000kg to 12,000kg.

Thus, the bogies 100 may be designed for supporting a rail-based vehicle having a weight of no more than 20,000kg, e.g. less than 17,000kg, e.g. less than 12,000kg (e.g. if excluding passenger weight).

One inventive aspect of the present invention is the recognition that an open differential (particularly those designed for an automotive vehicle such as a car) can be used in circumstances where the weight of the rail-based vehicle is relatively low.

Although embodiments describe the use of electric motors for driving the rail wheel(s), the skilled person would appreciate that other forms of motor could be used to drive the rail wheels, e.g. combustion engines, hydrogen-based motors or the like.

Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS: A bogie for a rail-based vehicle, the bogie comprising one or more rail wheel arrangements, each rail wheel arrangement comprising: a first rail wheel; a second, different rail wheel and an open differential connecting the first and second rail wheels together, so that the first and second rail wheels are driven simultaneously, but so that the first rail wheel is able to rotate at a different speed to the second rail wheel.
2. The bogie of claim I, wherein the one or more rail wheel arrangements comprises two or more rail wheel arrangements
3. The bogie of any of claims 1 to 2, wherein the open differential of each rail wheel arrangement is an open differential configured for use with a motor vehicle, such as a car.
4. The bogie of any of claims Ito 3, wherein the bogie is configured to support a rail-based vehicle having a weight no greater than 20,000kg.
5. The bogie of any of claims 1 to 4, wherein the open differential of each rail wheel arrangement does not comprise a limited slip differential or a locking differential.
6. The bogie of any of claims 1 to 5, wherein each rail wheel arrangement further comprises a wheel framework, comprising one or more lateral beams connected between the first and second rail wheel.
7. The bogie of any of claims I to 6, wherein each rail wheel arrangement comprises a different motor configured to drive the first and second rail wheel, of the rail wheel arrangement, using the open differential.
8. The bogie of claim 7, wherein each rail wheel arrangement comprises a gearbox connected between the motor of the rail wheel arrangement and the open differential of the rail wheel arrangement.
9 The bogie of claim 7 or 8, wherein the motor, of each rail wheel arrangement, is mounted together with the open differential of the rail wheel arrangement
10. The bogie of claim 9, wherein each rail wheel arrangement comprises a single mount for coupling both the open differential and the motor, of the rail wheel arrangement, to the remainder of the bogie.
11. The bogie of any of claims 7 to 10, wherein the motor of each rail wheel arrangement is configured to operate at a rotation speed of up to 8000 rotations per minute.
12 The bogie of any of claims 7 to 11, wherein the motor of each rail wheel arrangement is configured to provide a torque of up to 150Nm.
13. The bogie of any of claims 7 to 12, wherein the motor of each rail wheel arrangement is an electric motor. 20
14. The bogie of claim 13, wherein the electric motor of each rail wheel arrangement is configured to receive power from an inverter, wherein motors of different rail wheel arrangements receive power from different inverters.
15. A rail-based vehicle comprising two or more bogies according to any of claims Ito 14.
16. A rail-based vehicle comprising: two or more bogies according to any of claims 13 or 14; and a battery configured to provide power to the motor of each rail wheel arrangement.
17. The rail-based vehicle of claim 16, further comprising, for each rail wheel arrangement, a separate inverter for converting a DC voltage, provided by the battery, to an AC voltage for powering the motor of said rail wheel arrangement.
18 The rail-based vehicle of any of claims 16 or 17, wherein the overall weight of the rail-based vehicle is less than 20,000kg.