SE543630C2

SE543630C2 - System for electrical feeding of road vehicles

Info

Publication number: SE543630C2
Application number: SE1951045A
Authority: SE
Inventors: Gunnar Asplund
Original assignee: Elways Ab
Priority date: 2019-09-16
Filing date: 2019-09-16
Publication date: 2021-04-27
Also published as: SE1951045A1; WO2021052947A1; EP4031399A1

Abstract

A system (1) for electrical feeding of electrically propellable road vehicles (2) is provided. The system comprises a rail element (4) having at least one electric conductor (4a, 4b) extending in a lengthwise direction thereof and a current collector (3) adapted to co-act with the rail element. The at least one electric conductor is arranged in at least one groove (4’, 4”) in the rail element and is adapted to be put under voltage. The rail element (4) is adapted to be located in a road section (5) on which the vehicle is travelling, wherein the current collector (3) is connectable to the vehicle and is displaceable vertically and laterally and comprises at least one contact element (3a, 3b). Each contact element is adapted to connect mechanically and electrically with a corresponding contact portion of the at least one electric conductor. The contact element (3a) and at least the contact portions of the electric conductors (4a, 4b) have a hardness being higher than that of quartz.

Description

SYSTEM FOR ELECTRICAL FEEDING OF ROAD VEHICLES TECHNICAL FIELD The invention relates to a system for electrical feeding of electrically propellable roadvehicles using a rail element with electric conductors located in a road section onwhich the vehicle travels.

BACKGROUND Concerns about the environmental impact of combustion of fossil fuels have ledto an increased interest in electric vehicles, which have several potential benefitscompared to vehicles with conventional internal combustion engines, including: asignificant reduction of urban air pollution, as they do not emit harmful tailpipepollutants from the on-board source of power at the point of operation; reducedgreenhouse gas emissions from the on-board source of power, depending on the fueland technology used for electricity generation and/or charging the batteries andreduced dependency on fossil fuels with increasingly variable supply and fluctuatingpnces.

However, the expense, weight and limited capacity of the lithium-ion batterypacks of today limit widespread use of electric power as the main source of power invehicles.

WO 2011/123049 proposes complementing the battery of the electric vehiclewith electric feeding of the vehicle while driving. A system is disclosed for electricpropulsion of a vehicle along a road comprising rail elements/structures havinggrooves provided with electric conductors therein that may be put under voltage andlocated in longitudinal tracks or channels in the road. The vehicle is equipped with acurrent collector which during contact with the electric conductors allows for transferof electric power between the electric conductors and the vehicle to propel thevehicle and charge its battery or set of batteries.

The stretch of road carrying the rail elements is divided into electricallyseparated road sections oriented in series, whereby the rail elements are only putunder voltage when a vehicle with its current collector passes the relevant roadsecüon. ln such systems, it is important that the groove(s) are kept clean. The applicanthas identified this problem previously, and has proposed a cleansing device, as disclosed in EP2994337B1, to clean the grooves and allow good electric contact. lnpractical implementations, the durability of the current collector and/or of the railelement has proven unsatisfactory under certain circumstances, with high wear of thecontact elements and/or of the rail element despite using a cleansing device.

SUMMARYAn object of the invention is to provide a system for electrical feeding of road vehicleshaving improved durability.

These and other objects are achieved by the present invention by means of a systemaccording to the independent claim.

According to the invention, a system for electrical feeding of electrically propellableroad vehicles is provided. The system comprises a rail element having at least oneelectric conductor extending in a lengthwise direction thereof and a current collectoradapted to co-act with the rail element. Each of the at least one electric conductor isarranged in at least one groove in the rail element, for instance in a respectivegroove, and is adapted to be put under voltage for supplying electric power to thevehicle. The rail element is adapted to be located in a road section on which thevehicle is travelling, wherein the current collector is connectable to the vehicle and isdisplaceable vertically and laterally and comprises at least one contact element. Eachcontact element is adapted to connect mechanically and electrically with acorresponding contact portion of the at least one electric conductor. The contactelement and at least the contact portions of the electric conductors have a hardnessbeing higher than that of quartz. ln other words, a system is provided where the contact element, or at least portion(s)thereof šs~~adapted to connect with contact portion(s) of the electric conductor(s), andthe contact portion(s) of the electric conductors(s) (or the electric conductors as awhole) have a hardness being higher than that of quartz. Put differently, the hardnessis more than 7 on the Mohs hardness scale, or equivalent hardness on anotherhardness scale. lt is understood that the above-mentioned contact portion of the electric conductormay refer to a surface portion of the electric conductor, or to a coating on the electricconductor, or to a thicker wear layer on the electric conductor. lt is furthermoreunderstood that the contact portion is a portion of the electric conductor whichextends in its longitudinal direction, i.e. a portion which the contact element makescontact with while the vehicle is driving along the road section.

The invention is based on the insight that a major cause of wear on the contactelements of the current collector and the contact portions of the electric conductors issand, mostly consisting of quartz, which sticks to the inner surfaces of the groove(s)of the rail element when these surfaces are wet. The inventor has realized that sucha mixture of sand and water adhering to the inner surfaces is difficult to remove usingknown cleansing devices in the grooves, and further that the contact element and thecontact portions of the electric conductors therefore need to have a greater hardness than quartz. ln embodiments, the at least one contact element and the corresponding contact portion of the at least one electric conductor the same hardness ormade from the same material. Alternatively, the at least one contact element mayhave a greater hardness than the corresponding contact portion of the at least oneelectric conductor. According to conventional practise in the technical field, thecontact elements of the current collector, being in sliding contact with the contactportions of the rail element, should have a lower hardness than the rail element, suchthat the (easy to replace) contact elements are worn down rather than the railelement. These embodiments are based on the insight that by overcoming thistechnical prejudice, and instead providing contact elements of equal, or even higher,hardness than the electric conductors, a greatly improved durability may be achievedin this application. The contact element(s), or at least contact portions thereof beingadapted to connect with contact portion(s) of the electric conductor(s), mayadvantageously be provided with rounded edges, for instance having a radius in therange of 1-5 mm, to avoid damaging the contact portion(s). This is particularlyadvantageous in embodiments where the contact element(s) have a greaterhardness than the contact portion(s). ln embodiments, the at least one contact element, or at least contact portion(s) thereofis adapted to connect with contact portion(s) of the electric conductor(s), has ahardness of more than 7.5 on the Mohs hardness scale (or equivalent hardness onanother hardness scale), for instance by being made from hardened stainless steel.Such a hardness provides a contact element being clearly harder than most sandparticles which may be present in the grooves. The at least one contact element mayhave an even higher hardness and consist of, or comprise, a material having ahardness higher than that of hardened stainless steel or having a hardness of morethan 8 on the Mohs hardness scale (or equivalent hardness on another hardnessscale), for example a material being or comprising tungsten carbide, silicon carbide,chromium carbide or boron nitride. ln embodiments, the contact element comprisesparticles of a hard material (for example tungsten carbide) embedded in a softer material (such as chromium). ln embodiments, the contact portions of the at least one electric conductor has ahardness of more than 7.5 on the Mohs hardness scale (or equivalent hardness onanother hardness scale), for instance by being made from hardened stainless steel. lnother embodiments, the contact portion comprises or consists of a coating of a materialhaving a higher hardness than hardened stainless steel, or having a hardness of morethan 8 or more than 9 on the Mohs hardness scale, or equivalent hardness. Thematerial may comprise tungsten carbide, silicon carbide, chromium carbide or boronnitride or particles thereof embedded in a softer material. ln embodiments, the current collector comprises at least one rotatable wheel, eachcomprising (or constituting) one of the at least one contact element, each rotatablewheel being configured to roll against the corresponding contact portion of the at leastone electric conductor to make contact therewith. Using such a rotatable wheel, wearis further reduced (compared to using a sliding contact) and/or a less expensive (lesshard) material may be used to manufacture the contact element. The wheel may beconfigured to rotate passively, i.e. by means of friction against the correspondingcontact portion of the at least one electric conductor. Alternatively, the current collectormay comprise at least one electric motor configured to rotate the at least one rotatablewheel. This further reduces wear since the rotation speed of the wheel can be adjusted to reduce any sliding or slipping between the wheel and the conductor. The rotatable wheel may furthermore be mechanically and electrically attached to a rotational axle,wherein a sliding contact element is arranged in sliding contact with the axle at anopposite end to the wheel, which sliding contact is configured to connect the wheelelectrically to the vehicle.

In embodiments, the at least one electric conductor, or at least contact portion(s)thereof, is disposed on a respective vertical side wall portion of groove(s) in the railelement, and the current collector is configured to press the at least one contactelement against a corresponding contact portion of the electric conductor(s). Thisfurther reduces wear compared to having the electric conductor(s) at a bottom of acorresponding groove. These embodiments are advantageously combined with theabove described embodiments comprising rotatable wheel(s), which in suchcombined embodiments are arranged to rotate around a respective vertical axis of rotation.

The features of the embodiments described above are combinable in any practicallyrealizable way to form embodiments having combinations of these features.

BRIEF DESCRIPTION OF THE DRAWINGSAbove discussed and other aspects of the present invention will now be described inmore detail using the appended drawings, which show presently preferredembodiments of the invention, wherein: fig. 1 shows a schematic cross section view of an embodiment of a systemaccording to the invention, fig. 2a shows a schematic cross section view of parts of anotherembodiment of a system according to the invention, fig. 2b shows a top view of the embodiment in fig. 2a, and fig. 3 shows parts of another embodiment of a system according to the invenﬁon.

DETAILED DESCRIPTIONFig. 1 shows a schematic cross section view of an embodiment of a system 1 accordingto the invention. The figure shows an electrically propellable vehicle 2 which however is not part of the system according to the invention. The system comprises a current collector 3 and a rail element 4 comprising two electric conductors 4a, 4b, eacharranged in a corresponding groove 4', 4" in the rail element. ln the figure, the railelement is greatly exaggerated in size for clarity reasons. The electric conductors areput under voltage for supplying electric power to the vehicle. From the cross sectionshown in fig. 1, it is understood that the conductors 4a-b extend in the longitudinaldirection of the rail element. The current collector 3 is connectable to the vehicle 2 andis provided with contact elements 3a, 3b each arranged at a lower end of acorresponding collector arm extending into the grooves 4', 4". The contact elements3a, 3b are configured to be brought in electrical and mechanical contact with acorresponding conductor 4a, 4b. The contact elements 3a, 3b make sliding contactwith a vertical wall portion of the corresponding conductor 4a, 4b, which in thisembodiment are provided as U-shaped beams or profiles at the bottom of the grooves4', 4". ln other embodiments, the conductors 4a, 4b may be plate- or rod-shaped orthe like and be disposed on or in vertical side wall portions of the grooves 4', 4", while the contact elements make contact in the same manner as shown in fig. 1.

According to the invention, the contact elements 3a, 3b and the electric conductors4a, 4b all have a hardness being higher than that ofquartz (i.e. more than 7 on theMohs hardness scale). ln this embodiment, the contact elements 3a, 3b are madefrom a material comprising tungsten carbide (which has a hardness of about 9 on theMohs scale), while the electric conductors are made from hardened stainless steel(i.e. having a hardness of about 7.5-8 on the Mohs scale). The contact elements thus have greater hardness than the electric conductors.

Fig. 1 further shows that the rail element 4 is provided with electrically conductingground conductors 4c, 4d connected to ground potential. The ground conductors areprovided as a single U-shaped unit made from electrically conducting metal arrangedat a top centre portion of the rail element between the grooves 4', 4" with its shanksextending downwards into the respective groove. The ground contact elements 3c,3d are configured to be brought in electrical and mechanical contact with acorresponding ground conductor 4c, 4d. The at least one ground contact element iselectrically connected to a chassis and/or body portion 2' of the vehicle. The groundcontact elements make contact with vertical wall portions of the ground conductors4c, 4d. The ground contact elements 4a, 4b are made from a softer material than the contact elements 3a, 3b, for example graphite , and the ground conductors are alsomade from a softer material than the electric conductors, for example copper The useof softer materials is possible since the ground contact elements in this embodimentare only brought in contact with the ground conductors at low speeds, such as below20 km/h, thereby causing much less wear. ln other embodiments, the ground contactelements and the ground conductors are made from corresponding materials as the contact elements and the electric conductors.

Although not illustrated in fig. 1, the system is advantageously furthermore providedwith one or more cleansing means comprising a front portion inclined at an acuteangle with respect to the bottom part of the cleansing device to clean the groove(s)from particles and loose objects. Such cleansing means is described in further detailin applicants' patent EP2994337B1.

Fig. 2a shows a schematic cross section view of parts of another embodiment of asystem according to the invention, and fig. 2b shows a top view of the embodiment infig. 2a. ln this embodiment, the current collector 13 comprises contact elements 13a,13b in the form of rotatable wheels being rotatable around a substantially vertical axisof rotation coinciding with collector arms or shafts 16a, 16b. ln the same manner as infig. 1, the rail element 14 is provided with grooves 14', 14” in which electric conductors14a, 14b are arranged. Unlike the embodiment in fig. 1, the contact portions of theelectric conductors are provided in the form ofa wear layers 14a', 14b', which may alsobe referred to as coating, provided at opposite vertical wall portions of the electricconductors 14a, 14b. ln this embodiment, the wheels 13a, 13b rotate passively, i.e. by means of frictionbetween the wheels and the conductors caused by relative longitudinal movementbetween the vehicle and the conductors. ln other embodiments, the system maycomprise one or motors which rotates the wheels to have the same peripheral speedas the vehicle speed.

The peripheral surface of wheels 13a, 13b are made from a material or steelcomprising tungsten carbide particles, while the contact portions 14a', 14b' of theelectric conductors are made from hardened stainless steel (i.e. having a hardness of about 7.5-8 on the Mohs scale). ln other embodiments, particularly embodimentsintended for heavy traffic conditions, the contact portions may also comprise harder materials such as tungsten or chromium carbides to further improve durability.

Although fig. 2 only shows contact elements, it is understood that this embodiment mayalso comprise ground contact elements corresponding to the ground contact elements 3c, 3d in fig. 1, although being contact elements of the same type as wheels 13a, 13b.

Fig. 3 shows parts of another embodiment of a system according to the invention. Theembodiment corresponds to the embodiment in fig. 2, with the difference being in themechanical design of the current collector, where fig. 3 illustrates a contact element inthe form of a rotatable wheel 23a (corresponding to wheel 13a in fig. 2). The wheel isattached mechanically and electrically at a lower end of a rotational axle 26a arrangedrotatably inside a tube 27a adapted to be fixedly attached to the vehicle. A radiallydirected sliding contact element 28a is arranged in sliding contact with an upper endof the axle 26a. The sliding contact element 28a is electrically connectable to thevehicle to connect the wheel 23a electrically to the vehicle. The materials of wheel 23aand its corresponding electric conductor correspond to those in fig. 2.

The description above and the appended drawings are to be considered as nonlimiting examples of the invention. The person skilled in the art realizes that severalchanges and modifications may be made within the scope of the invention. Forexample, the rail element may comprise one or more further electric conductor(s), forinstance three conductors to provide a three-phase alternating current feed.Furthermore, the electric conductor(s) and ground conductor(s) may have a differentcross section than shown in figs. 1-2. ln particular, it is noted that differentcombinations of materials of the contact elements and conductors are foreseeablewithin the scope of the invention.

Claims

1. _ System (1) for electrical feeding of electrically propellable road vehicles (2)comprising a rail element (4; 14) having at least one electric conductor (4a, 4b;14a, 14b) extending in a lengthwise direction thereof and a current collector (3,13) adapted to co-act with said rail element, said at least one electricconductor being arranged in at least one groove (4', 4"; 14', 14") in said railelement and being adapted to be put under voltage for supplying electricpower to said vehicle, said rail element (4; 14) being adapted to be located ina road section (5) on which the vehicle is travelling, wherein the currentcollector is connectable to said vehicle and is displaceable vertically andlaterally and comprises at least one contact element (3a, 3b; 13a, 13b), eachcontact element being adapted to connect mechanically and electrically with acorresponding contact portion of the at least one electric conductor, wherein the contact element (3a, 3b; 13a, 13b) and at least the contactportions of the electric conductors (4a, 4b; 14a, 14b) have a hardness of more than 7 on the Mohs hardness scale. _ System according to claim 1, wherein the at least one contact element (3a, 3b; 13a, 13b) has a greater hardness than the corresponding contact portion ofthe at least one electric conductor (4a, 4b; 14a, 14b). System according to claim 1, wherein the at least one contact element (3a, 3b;13a, 13b) and the corresponding contact portion of the at least one electric conductor the same hardness. _ System according to claim 1, wherein the at least one contact element (3a, 3b; 13a, 13b) and the corresponding contact portion of the at least one electricconductor are of the same material. System according to claim 1, wherein the at least one contact element (3a, 3b;13a, 13b) has a hardness of more than 7.5 on the Mohs hardness scale. _ System according to claim 1, wherein the at least one contact element (3a, 3b; 13a, 13b) consists of or comprises a material having a hardness higher thanthat of hardened stainless steel, such as tungsten carbide, silicon carbide or boron nitride. 7. System according to any of the preceding claims, wherein the contact portionof the at least one electric conductor has a hardness of more than 7.5 on the Mohs hardness scale. _ System according to any of claims 1-6, wherein the contact portion of the at least one electric conductor is made from hardened stainless steel. System according to any of claims 1-6, wherein the contact portion comprisesor consists of a coating of a material having a higher hardness than hardenedstainless steel. 10.System according to any of the preceding claims, wherein the at least one 11 contact element (3a, 3b) is formed as a sliding contact configured to slideagainst said corresponding contact portion of the at least one electricconductor to make contact therewith. .System according to any of claims 1-9, wherein the current collector comprises at least one rotatable wheel (13a, 13b; 23a), each comprising oneof said at least one contact element, each rotatable wheel being configured toroll against said corresponding contact portion (14a', 14b') of the at least oneelectric conductor (14a, 14b) to make contact therewith. 12.System according to claim 11, wherein said current collector comprises at least one electric motor configured to rotate said at least one rotatable wheels(13a, 13b; 23a). 13.System according to any of the preceding claims, wherein the at least one electric conductor (4a, 4b; 14a, 14b) and/or the at least one contact portion isdisposed on a respective vertical side wall portion of the rail element (4; 14),and wherein the current collector is configured to press the at least one contact element (3a, 3b; 13a, 13b) against a corresponding electric conductor. 14.System according to claim 13 as dependent on claim 11 or 12, wherein said at least one rotatable wheel (13a, 13b; 23a) is arranged to rotate around arespective vertical axis of rotation. 15.System according to claim 14, wherein said rotatable wheel is electrically and mechanically connected to an axle (26a), wherein a sliding contact (28a) isarranged in sliding contact with the axle to provide electrical contact betweensaid rotatable wheel (13a, 13b; 23a) and the vehicle.