GB2494881A - Rail vehicle steering and suspension system - Google Patents

Abstract

The system has two opposite independently sprung and steerable flangeless wheels 13, 14 on the same axle line, each having an associated flanged wheel 15, 16 controllably liftable at points &c to enable the vehicle to be used on railway tracks without gaps in the rails. The rail vehicle is able to steer using reaction forces of the flangeless wheel/rail contact patches only. Loads on the wheels 13,14,15,16 can be varied by means of respective hydraulic rams, using control circuits, to steer the vehicle. Hydraulic rams are used to provide the lifting of the flanged wheels.

Description

Steering of rail vehicles using controlled, variable rail/wheel interface forces

Background

This invention relates to railway systems and their wheellrail interface.

Conventional rail vehicles can only travel in a straight line, or a line determined by the curvature and superelevation of the rails. Divergence from this line can be achieved by wheel/rail contact at the gauge corner, or by flange/rail contact, both accompanied by heavy wear, excessive energy consumption, and noise. Due to the presence of the wheel flange, rails are also discontinuous and require moving parts -point ends and the like -to effect mute setting.

Statement of Invention

To eliminate wheel and rail contact at any other point than on the lyre face, and to provide for continuous rails, this present invention proposes the use of two pairs of independently suspended steerable wheels of opposite tyre taper on each axle line, whose loadings and other operational parameters can be individually varied by a suitable control system to provide the required steering and other forces, with the outer pair flanged and capable of being raised independently as required by more than the depth of that flange at switches and crossings.

Advantages 1. When steel wheels roll on steel rails under ideal conditions, with the tyre faces normal to the rail head and with no gauge corner or flange contact, rolling resistance is very low -a child can easily tow 150 tons of locomotive, As soon as this ideal relationship is altered, by curvature under or over the balancing speed for the curve, or at flat switch and crossing works, rolling resistance and wear rises sharply. By varying the loads on the four wheel faces to exactly balance the centrifugal, and other forces, to the curve being negotiated, all rail/wheel contact other than that ideal is eliminated, and the resistance of vehicles traversing curves and switches will be reduced to the variation in the vectors caused by the change of direction.

2.At conventional switches the forces required to make a rail vehicle take the diverging route are normally provided by the gauge corner, and not infrequently, the flange as well. Most switch and crossing work can have no, or very limited, superelevation, so transit speeds on the diverging route must be either very low, or the divergence slight and the point ends very long. Most divergences are low speed in order to keep the cost of the switch to a minimum. The invention pennits rail vehicles to take the diverging route at a balancing speed for that divergence, even when the actual divergence has no superelevajion. Speeds under the theoretical balancing speed can also be taken without resort to gauge corner or flange contact, by varying the loads on the respective wheels, a process dealt with automatically by the vehicle control and feedback systems. At switches and crossings existing rail vehicles must cross a gap in the rails, provided to allow the wheel flanges to pass. The use of independently controlled flanged wheels permits the fouling flange to be lifted clear at junctions and allows the rails -and thus the wheel support -to be continuous at all points.

This will eliminate much wear and tear and shock damage to nmning lines and wheels.

3.Conventional switches and crossings have moving parts. The invention enables them to be replaced with fixed equipment requiring no more maintenance than plain line. Trackside power -electrical or otherwise -to move point ends or crossing blades, is not required.

Advantages (conk!) 4. Existing rail vehicles rely mainly on four wheel trucks -bogies -to maintain the wheels radial to curves. On curves with very short radii this system cannot keep the wheels sufficiently radial to prevent gauge corner and flange contact, leading to a dramatic increase in rolling resistance, a particular problem on underground and on-street rapid transit systems with tight curves. The invention proposes to maintain the attitude of the wheels in an ideal radial position at all times by the linking of the individual wheels on any one axle line to an Ackerman-type steering gear linked to the wheel control system.

5. Bogies could be used to mount the invention, but the system is proposed as being mounted directly on the vehicle body, giving independent suspension and eliminating the weight of the two bogies normally needed for a rail vehicle, 6. With the elimination of the reactive forces between a solid axle carrying a pair of wheels, and the pair of rails it runs on, the tendency of that wheel and axle combination and the t/re taper to force the rails apart, is eliminated. This removes the need for most of the cross ties between rail pairs. All forces, except at divergences, are normal to the sleeper/tie interface. Rails can thus be continuously supported on longitudinal bearers rather than cross-ties, without numerous additional ties, eliminating the bending and shear forces, and the hammer blow, that cross-tie supported rails generate on the SI/tie/ballast interfaces. Track maintenance costs will therefore fall perhaps by as much as 90% over existing -with the adoption of alternative track formats taking advantage of the system's possibilities.

7. The elimination of the solid axle and the introduction of independent suspension will both improve the rail vehicle ride and reduce the unsprung weight -the cause of most track wear and damage -as part of a virtuous cycle of weight reduction.

8. With the invention's ability to permit rail vehicles to traverse tight curves without gauge corner or flange contact, and at speed, the need to segregate street running light rail systems to superelevate curves is eliminated. Light rail can cross streets at a curve -needed within tight urban infrastructure -without offering unacceptable variations in the pavement profile that would cause hazards to other highway users, or very low speeds that would obstruct traffic.

9. The ability of the invention to vary loads between wheels on an axle line, permits the vehicle control systems to interface with the drivetrain to prevent wheelslip, enabling the driven wheels to be given additional loads as required. All wheels in an axle-line wheelset do not therefore need to be driven.

10. The invention permits all train control to be vehicle based, eliminating on segregated formations trackside and on-track control equipment and power supplies thereto. This opens the prospect of train to train communication and control, optimisation of tirnetabling in real time to minimise delays and energy consumption, at-speed formation and splitting of services, and perhaps a ten-fold increase in existing line of route capacity.

Introduction to Drawings

The following drawings describe a way of constructing the invention:-Figure 1 is a general transverse section Figure 2 is a plan view Figure 3 is a fluid control circuit showing the principles of wheel force management Figure 4 is a schematic of the load control arrangement at the top of the macpherson strut Figure 5 is a schematic of the device for lifting the outer wheels to give flange clearance at switches and cross ings Figure 6 is a schematic of the inputs, outputs, stored information and external interfaces of the control unit.

Detailed Description

Figure 1 shows a transverse section through the invention's mechanical components, using for the purpose of demonstration -other components or suspension arrangements suitably modified could perform the same or similar tasks -conventional motor industry components forming what is known as a Macpherson Strut suspension. The inner section 1 is a standard independently sprung transaxie comprising final drive unit 4, half shafts 5&6, lower wishbones 7&8, coil spring and shock absorber units 9&10, and top swivel bearings 1 l&12. Bottom swivel bearings and various other standard details are omitted for clarity. Rail wheels l3&14 are bolted on in place of the normal pneumatic wheel and tyre, and have conventionS 1:20 tapered steel tyres but no flanges.

Outside this conventional transaxie are two undriven axle and suspension units 2&3, each identical to and a mirror image of the axle and suspension half units forming the transaxie, lacking the driven half shafts of the inner wheelset, but having an outer extension (not shown -see figs) to the! lower wishbones 3 l&32. To these axle and suspension units are attached nil wheels 15&16, which have 1:20 tapered tyres of opposite taper to normal, and outside flanges. Whilst the inner and outer suspension units are shown as being the same, the invention does not depend upon this -different suspension units could be combined on the same axle line if so desired. The purpose of the suspension units is to permit each wheel to be separately loaded according to need.

Figure 2 shows a plan view through the invention's mechanical components with radius arrnsl7,l8,19&20 attached to and controlling the movement of the macpherson struts, being connected to a power driven rack and pinion steering set 21 via conventional ball joints. Also shown are the lower inner and outer wishbones7,8, 31,32, but the coil springs and swivel joints are omitted, as are various other details not relevant to this application such as tracking adjustment and wheelspinlslide monitoring.

Detailed Description (contd)

Figure 3 is a schematic arrangement of the proposed suspension fluid control system. This is shown as an hydraulic system, but other fluids -such as compressed air -or other systems -electrical or elctromagnetic -could be used with equal effect. The control system is split into four sections.

l)Each wheel suspension unit has an hydraulic ram 34 fitted between the top of the macpherson strut and the the suspension spring. This allows the spring to be adjusted in operating length, independent of any motion forces, to carry between nil and one half of the nominal axle load of the transaxle. 2) Each wheel pair of hydraulic cylinders for suspension units 22 and 23 -left hand, and 24 and 25 -right hand, is connected to a master cylinder: 26 left hand, 27 right hand, which are in two fluid compartments connected by a power driven rack and pinion 36 of fixed length, connected to two pistons 37. These pistons 37 move in tandem to adjust the load between the wheels in a pair.

Pressure sensors in the feed lines provide infonnation to the central processor which controls the overall operation via the servomotors driving the rack and pinions 36.3) Connecting both master cylinders 26&27 is a pair of tandem tilt cylinders 28, whose construction and operation is similar to the master cylinders, and whose forces act upon floating pistons 35 in the free ends of the master cylinders 26 & 27 to control the vehicle tilt, either into curves or in response to side wind pressure or other forces. 4) Controlling the whole actuation of this system is a central processor fig 6, computer based, which takes the information stored about the track and mute geometry and instructs the wheelset controls in accordance with the various real time inputs -speed, location, route, load, wind pressure and direction, and other information on traffic on possible route conflicts, running schedule etc. Figure 4 is a schematic section through the top of the macpherson strut, showing the modification from standard automotive practice to insert a floating top bearer 29 for the coil spring 30 so that the hydraulic ram 34 can adjust the coil spring length, and thus the loadings, as required.

Figure 5 is a schematic of the outer wishbones 3 1,32, showing the outer extension to provide for lifting the flange clear of the rails when crossing switches etc. Under normal operation the hydraulic ram 33, or other operating mechanism, is idle, and moves with the general suspension dynamics.

When required to lift the outer wheels 15,16 fig!, the load on rnacpherson strut units 9a,lOa fig I is removed by the effects of the control system described in fig 3, and the required ram 33 is then activated to lift the wheel flange clear of the crossing rail. The ram 33 is only required to lift the mass of the wheel and suspension, not any part of the vehicle sprung weight.

Figure 6 is a diagram of the control inputs and outputs required to be processed/stored by the control system. Other information not relevant to this application may also be processed.

Claims (2)

1. <claim-text>SFirst Claim 1. A rail vehicle wheel, suspension and control system to optimise wheel/rail contact, and eliminate moving parts and gaps in the supporting rails.</claim-text> <claim-text>Dependent Claims
2. 2. A system, according to claim 1, that permits rail vehicles to take diverging routes on non-superelevated junctions at a balancing speed, without significantly compromising the optimal wheel/rail contact zone.</claim-text> <claim-text>3. A system, according to claim 2, whereby the train is enabled to route set itself at junctions and turnouts.</claim-text>