EP4031399A1

EP4031399A1 - System for electrical feeding of road vehicles

Info

Publication number: EP4031399A1
Application number: EP20772277.8A
Authority: EP
Inventors: Gunnar Asplund
Original assignee: Elways AB
Current assignee: Evias AB
Priority date: 2019-09-16
Filing date: 2020-09-15
Publication date: 2022-07-27
Also published as: WO2021052947A1; SE543630C2; SE1951045A1

Abstract

A system for electrical feeding of electrically propellable road vehicles is provided. The system comprises a rail element having at least one electric conductor extending in a lengthwise direction thereof and a current collector adapted to co-act with the rail element. The at least one electric conductor is arranged in at least one groove in the rail element and is adapted to be put under voltage. The rail element is adapted to be located in a road section on which the vehicle is travelling, wherein the current collector is connectable to the vehicle and is displaceable vertically and laterally and comprises at least one contact element. 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 and at least the contact portions of the electric conductors 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 road vehicles using a rail element with electric conductors located in a road section on which the vehicle travels.

BACKGROUND

Concerns about the environmental impact of combustion of fossil fuels have led to an increased interest in electric vehicles, which have several potential benefits compared to vehicles with conventional internal combustion engines, including: a significant reduction of urban air pollution, as they do not emit harmful tailpipe pollutants from the on-board source of power at the point of operation; reduced greenhouse gas emissions from the on-board source of power, depending on the fuel and technology used for electricity generation and/or charging the batteries and reduced dependency on fossil fuels with increasingly variable supply and fluctuating prices.

However, the expense, weight and limited capacity of the lithium-ion battery packs of today limit widespread use of electric power as the main source of power in vehicles.

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

The stretch of road carrying the rail elements is divided into electrically separated road sections oriented in series, whereby the rail elements are only put under voltage when a vehicle with its current collector passes the relevant road section.

In such systems, it is important that the groove(s) are kept clean. The applicant has identified this problem previously, and has proposed a cleansing device, as disclosed in EP2994337B1 , to clean the grooves and allow good electric contact. In practical implementations, the durability of the current collector and/or of the rail element has proven unsatisfactory under certain circumstances, with high wear of the contact elements and/or of the rail element despite using a cleansing device.

SUMMARY

An object of the invention is to provide a system for electrical feeding of road vehicles having improved durability.

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

According to the invention, a system for electrical feeding of electrically propellable road vehicles is provided. The system comprises a rail element having at least one electric conductor extending in a lengthwise direction thereof and a current collector adapted to co-act with the rail element. Each of the at least one electric conductor is arranged in at least one groove in the rail element, for instance in a respective groove, and is adapted to be put under voltage for supplying electric power to the vehicle. The rail element is adapted to be located in a road section on which the vehicle is travelling, wherein the current collector is connectable to the vehicle and is displaceable vertically and laterally and comprises at least one contact element. 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 and at least the contact portions of the electric conductors have a hardness being higher than that of quartz.

In other words, a system is provided where the contact element, or at least portion(s) thereof is adapted to connect with contact portion(s) of the electric conductor(s), and the contact portion(s) of the electric conductors(s) (or the electric conductors as a whole) have a hardness being higher than that of quartz. Put differently, the hardness is more than 7 on the Mohs hardness scale, or equivalent hardness on another hardness scale. It is understood that the above-mentioned contact portion of the electric conductor may refer to a surface portion of the electric conductor, or to a coating on the electric conductor, or to a thicker wear layer on the electric conductor. It is furthermore understood that the contact portion is a portion of the electric conductor which extends in its longitudinal direction, i.e. a portion which the contact element makes contact 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 contact elements of the current collector and the contact portions of the electric conductors is sand, 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 such a mixture of sand and water adhering to the inner surfaces is difficult to remove using known cleansing devices in the grooves, and further that the contact element and the contact portions of the electric conductors therefore need to have a greater hardness than quartz.

In embodiments, the at least one contact element and the corresponding contact portion of the at least one electric conductor has the same hardness or is made from the same material. Alternatively, the at least one contact element may have a greater hardness than the corresponding contact portion of the at least one electric conductor. According to conventional practise in the technical field, the contact elements of the current collector, being in sliding contact with the contact portions of the rail element, should have a lower hardness than the rail element, such that the (easy to replace) contact elements are worn down rather than the rail element. These embodiments are based on the insight that by overcoming this technical prejudice, and instead providing contact elements of equal, or even higher, hardness than the electric conductors, a greatly improved durability may be achieved in this application. The contact element(s), or at least contact portions thereof being adapted to connect with contact portion(s) of the electric conductor(s), may advantageously be provided with rounded edges, for instance having a radius in the range of 1-5 mm, to avoid damaging the contact portion(s). This is particularly advantageous in embodiments where the contact element(s) have a greater hardness than the contact portion(s). In embodiments, the at least one contact element, or at least contact portion(s) thereof is adapted to connect with contact portion(s) of the electric conductor(s), has a hardness of more than 7.5 on the Mohs hardness scale (or equivalent hardness on another hardness scale), for instance by being made from hardened stainless steel. Such a hardness provides a contact element being clearly harder than most sand particles which may be present in the grooves. The at least one contact element may have an even higher hardness and consist of, or comprise, a material having a hardness higher than that of hardened stainless steel or having a hardness of more than 8 on the Mohs hardness scale (or equivalent hardness on another hardness scale), for example a material being or comprising tungsten carbide, silicon carbide, chromium carbide or boron nitride. In embodiments, the contact element comprises particles of a hard material (for example tungsten carbide) embedded in a softer material (such as chromium).

In embodiments, the contact portions of the at least one electric conductor has a hardness of more than 7.5 on the Mohs hardness scale (or equivalent hardness on another hardness scale), for instance by being made from hardened stainless steel. In other embodiments, the contact portion comprises or consists of a coating of a material having a higher hardness than hardened stainless steel, or having a hardness of more than 8 or more than 9 on the Mohs hardness scale, or equivalent hardness. The material may comprise tungsten carbide, silicon carbide, chromium carbide or boron nitride or particles thereof embedded in a softer material.

In embodiments, the current collector comprises at least one rotatable wheel, each comprising (or constituting) one of the at least one contact element, each rotatable wheel being configured to roll against the corresponding contact portion of the at least one electric conductor to make contact therewith. Using such a rotatable wheel, wear is further reduced (compared to using a sliding contact) and/or a less expensive (less hard) material may be used to manufacture the contact element. The wheel may be configured to rotate passively, i.e. by means of friction against the corresponding contact portion of the at least one electric conductor. Alternatively, the current collector may comprise at least one electric motor configured to rotate the at least one rotatable wheel. 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 an opposite end to the wheel, which sliding contact is configured to connect the wheel electrically 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 rail element, and the current collector is configured to press the at least one contact element against a corresponding contact portion of the electric conductor(s). This further reduces wear compared to having the electric conductor(s) at a bottom of a corresponding groove. These embodiments are advantageously combined with the above described embodiments comprising rotatable wheel(s), which in such combined embodiments are arranged to rotate around a respective vertical axis of rotation.

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

BRIEF DESCRIPTION OF THE DRAWINGS

Above discussed and other aspects of the present invention will now be described in more detail using the appended drawings, which show presently preferred embodiments of the invention, wherein: fig. 1 shows a schematic cross section view of an embodiment of a system according to the invention, fig. 2a shows a schematic cross section view of parts of another embodiment 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 invention.

DETAILED DESCRIPTION

Fig. 1 shows a schematic cross section view of an embodiment of a system 1 according to 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, each arranged in a corresponding groove 4’, 4” in the rail element. In the figure, the rail element is greatly exaggerated in size for clarity reasons. The electric conductors are put under voltage for supplying electric power to the vehicle. From the cross section shown in fig. 1 , it is understood that the conductors 4a-b extend in the longitudinal direction of the rail element. The current collector 3 is connectable to the vehicle 2 and is provided with contact elements 3a, 3b each arranged at a lower end of a corresponding collector arm extending into the grooves 4’, 4”. The contact elements 3a, 3b are configured to be brought in electrical and mechanical contact with a corresponding conductor 4a, 4b. The contact elements 3a, 3b make sliding contact with a vertical wall portion of the corresponding conductor 4a, 4b, which in this embodiment are provided as U-shaped beams or profiles at the bottom of the grooves 4’, 4”. In other embodiments, the conductors 4a, 4b may be plate- or rod-shaped or the 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 conductors 4a, 4b all have a hardness being higher than that of quartz (i.e. more than 7 on the Mohs hardness scale). In this embodiment, the contact elements 3a, 3b are made from a material comprising tungsten carbide (which has a hardness of about 9 on the Mohs 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 conducting ground conductors 4c, 4d connected to ground potential. The ground conductors are provided as a single U-shaped unit made from electrically conducting metal arranged at a top centre portion of the rail element between the grooves 4’, 4” with its shanks extending downwards into the respective groove. The ground contact elements 3c,

3d are configured to be brought in electrical and mechanical contact with a corresponding ground conductor 4c, 4d. The at least one ground contact element is electrically connected to a chassis and/or body portion 2’ of the vehicle. The ground contact elements make contact with vertical wall portions of the ground conductors 4c, 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 also made from a softer material than the electric conductors, for example copper The use of softer materials is possible since the ground contact elements in this embodiment are only brought in contact with the ground conductors at low speeds, such as below 20 km/h, thereby causing much less wear. In other embodiments, the ground contact elements 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 provided with one or more cleansing means comprising a front portion inclined at an acute angle 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 detail in applicants’ patent EP2994337B1.

Fig. 2a shows a schematic cross section view of parts of another embodiment of a system according to the invention, and fig. 2b shows a top view of the embodiment in fig. 2a. In this embodiment, the current collector 13 comprises contact elements 13a, 13b in the form of rotatable wheels being rotatable around a substantially vertical axis of rotation coinciding with collector arms or shafts 16a, 16b. In the same manner as in fig. 1, the rail element 14 is provided with grooves 14’, 14” in which electric conductors 14a, 14b are arranged. Unlike the embodiment in fig. 1 , the contact portions of the electric conductors are provided in the form of a wear layers 14a’, 14b’, which may also be referred to as coating, provided at opposite vertical wall portions of the electric conductors 14a, 14b.

In this embodiment, the wheels 13a, 13b rotate passively, i.e. by means of friction between the wheels and the conductors caused by relative longitudinal movement between the vehicle and the conductors. In other embodiments, the system may comprise one or motors which rotates the wheels to have the same peripheral speed as the vehicle speed.

The peripheral surface of wheels 13a, 13b are made from a material or steel comprising tungsten carbide particles, while the contact portions 14a’, 14b’ of the electric conductors are made from hardened stainless steel (i.e. having a hardness of about 7.5-8 on the Mohs scale). In other embodiments, particularly embodiments intended 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 may also 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. The embodiment corresponds to the embodiment in fig. 2, with the difference being in the mechanical design of the current collector, where fig. 3 illustrates a contact element in the form of a rotatable wheel 23a (corresponding to wheel 13a in fig. 2). The wheel is attached mechanically and electrically at a lower end of a rotational axle 26a arranged rotatably inside a tube 27a adapted to be fixedly attached to the vehicle. A radially directed sliding contact element 28a is arranged in sliding contact with an upper end of the axle 26a. The sliding contact element 28a is electrically connectable to the vehicle to connect the wheel 23a electrically to the vehicle. The materials of wheel 23a and its corresponding electric conductor correspond to those in fig. 2.

The description above and the appended drawings are to be considered as non limiting examples of the invention. The person skilled in the art realizes that several changes and modifications may be made within the scope of the invention. For example, the rail element may comprise one or more further electric conductor(s), for instance three conductors to provide a three-phase alternating current feed. Furthermore, the electric conductor(s) and ground conductor(s) may have a different cross section than shown in figs. 1-2. In particular, it is noted that different combinations of materials of the contact elements and conductors are foreseeable within 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 electric conductor being arranged in at least one groove (4’, 4”; 14’, 14”) in said rail element and being adapted to be put under voltage for supplying electric power to said vehicle, said rail element (4; 14) being adapted to be located in a road section (5) on which the vehicle is travelling, wherein the current collector is connectable to said vehicle and is displaceable vertically and laterally and comprises at least one contact element (3a, 3b; 13a, 13b), each contact element being adapted to connect mechanically and electrically with a corresponding contact portion of the at least one electric conductor, wherein the contact element (3a, 3b; 13a, 13b) and at least the contact portions of the electric conductors (4a, 4b; 14a, 14b) have a hardness of more than 7 on the Mohs hardness scale.

2. 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 of the at least one electric conductor (4a, 4b; 14a, 14b).

3. 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 has the same hardness.

4. 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 are of the same material.

5. 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.

6. 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 than that 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 portion of the at least one electric conductor has a hardness of more than 7.5 on the Mohs hardness scale.

8. 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.

9. System according to any of claims 1-6, wherein the contact portion comprises or consists of a coating of a material having a higher hardness than hardened stainless steel.

10. System according to any of the preceding claims, wherein the at least one contact element (3a, 3b) is formed as a sliding contact configured to slide against said corresponding contact portion of the at least one electric conductor to make contact therewith.

11. System according to any of claims 1-9, wherein the current collector comprises at least one rotatable wheel (13a, 13b; 23a), each comprising one of said at least one contact element, each rotatable wheel being configured to roll against said corresponding contact portion (14a’, 14b’) of the at least one electric 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 is disposed 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 a respective 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) is arranged in sliding contact with the axle to provide electrical contact between said rotatable wheel (13a, 13b; 23a) and the vehicle.