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Title:
SYSTEM AND METHOD FOR ELECTRICAL FEEDING OF ROAD VEHICLES
Document Type and Number:
WIPO Patent Application WO/2021/052948
Kind Code:
A1
Abstract:
A system comprising an electrically propellable vehicle and a rail element comprising at least one electric conductor arranged in at least one groove thereof and being adapted to be put under voltage for supplying electric power to the vehicle, and at least one electrically conducting ground conductor being connectable to ground potential. The vehicle is provided with a current collector adapted to co-act with the rail element, which is located in a road section on which the vehicle is adapted to travel, wherein the current collector is displaceable vertically and laterally and comprises at least one contact element and at least one ground contact element, being configured to be brought in electrical and mechanical contact with a corresponding electric conductor and ground conductor, respectively, wherein the at least one ground contact element is electrically connected to a chassis and/or body portion of the vehicle.

Inventors:
ASPLUND GUNNAR (SE)
Application Number:
EP2020/075743
Publication Date:
March 25, 2021
Filing Date:
September 15, 2020
Export Citation:
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Assignee:
ELWAYS AB (SE)
International Classes:
B60M1/34; B60L5/40; B61L25/02
Domestic Patent References:
WO2011123049A12011-10-06
Foreign References:
EP2994337A22016-03-16
DE60310983T22007-10-11
Attorney, Agent or Firm:
GROTH & CO KB (STOCKHOLM, SE)
Download PDF:
Claims:
CLAIMS

1. System (1 ) for electrical feeding of road vehicles, said system comprising an electrically propellable vehicle (2) and at least one rail element (4; 14; 24) comprising at least one electric conductor (4a, 4b; 14a, 14b) arranged in at least one groove (4’, 4”) in said rail element and being adapted to be put under voltage for supplying electric power to said vehicle, said at least one rail element being located in a road section (5) on which the vehicle (2) is adapted to travel, said vehicle comprising a current collector (3) adapted to co-act with said at least one rail element, wherein the current collector is displaceable vertically and laterally and comprises at least one contact element (3a, 3b;

13a, 13b) being adapted to connect mechanically and electrically with a corresponding electric conductor (4a, 4b; 14a, 14b), wherein said at least one rail element is provided with at least one electrically conducting ground conductor (4c, 4d; 14c; 24c, 24d) being connectable to ground potential, wherein said current collector comprises at least one ground contact element (3c, 3d; 13c; 23c, 23d), each being configured to be brought in electrical and mechanical contact with a corresponding ground conductor (4c, 4d; 14c; 24c, 24d), and wherein said at least one ground contact element is electrically connected to a chassis and/or body portion (2’) of said vehicle.

2. System according to claim 1 , wherein said at least one rail element (4; 24) is each provided with at least two electrically conducting ground conductors (4c, 4d; 24c, 24d) being connectable to ground potential, wherein said current collector comprises at least two ground contact elements (3c, 3d; 23c, 23d), each being configured to be brought in electrical and mechanical contact with a corresponding ground conductor.

3. System according to claim 2, further comprising control means (6) configured to:

- measure electrical resistance between said ground contact elements (3c, 3d; 23c, 23d);

- determine if the resistance is above a predetermined value; - provide, if the resistance is above said predetermined value, a warning signal indicating that the vehicle (2) is not sufficiently grounded.

4. System according to claim 3, wherein said control means (6) is further configured to send, in response to said warning signal, a control signal to release said at least one contact element (3a, 3b) from contact with said at least one electrical conductor (4a, 4b).

5. System according to claim 4, wherein said control means (6) is configured to send said control signal only if a vehicle speed is below a predetermined level.

6. System according to any of claims 2-5, wherein said ground conductors (4c, 4d; 24c, 24d) are disposed on vertical side wall portions of the at least one groove in said rail element, and wherein the current collector is configured to press the ground contact elements laterally towards said ground conductors to make contact therewith.

7. System according to claim 1 , wherein said at least one electrically conducting ground conductor (24c, 24d) is provided in at least one groove (24’”) in said rail (24) being separate from the at least one groove (24’, 24”) carrying the at least one electric conductor.

8. Method for electrical feeding of a road vehicle in a system according to claim 1, said method comprising:

- connecting (31 ) the at least one electric conductor to a source of electric power;

- connecting (32) the at least one electrically conducting ground conductor to ground potential, and

- displacing (33) the current collector vertically and/or laterally to connect mechanically and electrically with the at least one electric conductor and with the at least one ground conductor.

9. Method according to claim 8, where said system is a system according to claim 2, said method further comprising:

- disconnecting (41 ) said ground contact elements from electrical contact with said chassis and/or body portion of said vehicle;

- measuring (42) electrical resistance between said ground contact elements;

- determining (43) if the resistance is above a predetermined value; - providing (44), if the resistance is above said predetermined value, a warning signal indicating that the vehicle is not sufficiently grounded.

10. Method according to claim 9, further comprising:

- Sending (46), in response to said warning signal, a release control signal to said current collector

- using, in response to said release control signal, the current collector to release (47) said at least one contact element from contact with said at least one electrical conductor.

11. Method according to claim 10, wherein said step of sending comprises determining (45) a vehicle speed and sending said control signal only if said vehicle speed is below a predetermined level.

Description:
SYSTEM AND METHOD FOR ELECTRICAL FEEDING OF ROAD VEHICLES

TECHNICAL FIELD

The invention relates to a system and a method for electrical feeding of road vehicles, and a method for determining ground contact in such a system.

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 practical implementations of such systems, safety concerns have been raised concerning the risk that the vehicle body may be subjected to live voltage if an isolation error would occur. This may be solved by galvanically separating the electric current provided from the road from the vehicle, for example using a switching high frequency transformer arrangement. In case of an isolation error, the main safety issue is that the vehicle could risk subjecting pedestrians and other people in the vicinity of the vehicle to live voltage. Another solution is therefore to disable electric feeding of the vehicle at lower speeds, such as below 20 km/h.

SUMMARY

An object of the invention is to solve the safety problems discussed in the background section above in an improved manner.

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

According to a first aspect of the invention, a system for electrical feeding of road vehicles is provided. The system comprises an electrically propellable vehicle and at least one rail element comprising at least one electric conductor, such as two or three electric conductors, each being arranged in at least one groove in the rail element, for instance in respective grooves, the at least one electric conductor being adapted to be put under voltage for supplying electric power to the vehicle. The vehicle is provided with a current collector adapted to co-act with the at least one rail element, which is located in a road section on which the vehicle is adapted to travel, wherein the current collector is displaceable vertically and laterally and comprises at least one contact element, each being adapted to connect mechanically and electrically with a corresponding electric conductor. The at least one rail element is provided with at least one electrically conducting ground conductor being connectable to ground potential. The current collector comprises at least one ground contact element, each being configured to be brought in electrical and mechanical contact with a corresponding ground conductor, wherein the at least one ground contact element is electrically connected to a chassis and/or body portion of the vehicle.

In other words, the at least one rail element is, in addition to the at least one electric conductor, also provided with at least one ground conductor extending along the lengthwise direction thereof. The ground conductor(s) is/are not solely provided to ground the rail element itself, but co-acts with ground contact element(s) of the current collector which is electrically connected to a chassis and/or body portion of the vehicle. Since the vehicle is grounded, any isolation error can not result in the vehicle body or chassis being subjected to live voltage. Consequently, there is no need for galvanic separation, and electric feeding can be performed also at low speeds, or even standstill. As explained above, the ground contact element(s) are part of the current collector. The ground contact element(s) may alternatively be arranged on a separate ground collector which is displaceable laterally and vertically in the same sense as the current collector. Such a ground collector may however also be considered part of the current collector.

In order to maintain sufficient safety without using galvanic separation, it is important to ensure that electric contact with ground is maintained at all times. This may be achieved using two or more parallel connections to ground and control means configured to use these parallel connections, as will be described below.

In embodiments, the current collector comprises at least two ground contact elements, and the rail element is provided with at least two electrically conducting ground conductors, each being connectable to ground potential, where each ground contact element is configured to be brought in electrical and mechanical contact with a corresponding ground conductor. It is understood that the at least two electrically conducting ground conductors do not necessarily need to be two separate physical objects but may be formed as two portions or contact surfaces of a single electrically conducting object or conductor, e.g. that one conductor is provided with two ground contact surfaces. The system may furthermore comprise control means configured to:

- measure electrical resistance between the ground contact elements;

- determine if the resistance is above a predetermined value;

- provide, if the resistance is above said predetermined value, a warning signal indicating that the vehicle is not sufficiently grounded.

The predetermined resistance value may be in the range of 1-100 ohms.

It is understood that the step to measure is preceded by electrically disconnecting the ground contact elements from the vehicles’ chassis or body. The control means may furthermore be configured to send, in response to the warning signal, a control signal to the current collector, or displacement means configured to co-act with the current collector, to displace the current collector or at least parts thereof, to release the at least one contact element from contact with the at least one electrical conductor. In embodiments, the control signal is sent only if the vehicle speed is below a predetermined level, for instance 20 km/h.

In embodiments, the at least one ground conductor, or contact surface(s)/portion(s) of the ground conductor(s), is disposed on vertical side wall portion(s) of the at least one groove in the rail element, and the current collector is configured to press the corresponding ground contact element(s) laterally towards the ground conductor(s) to make contact therewith. In embodiments with two ground conductors, or a ground conductor having two contact surfaces, the ground conductors or contact surfaces are disposed on opposite vertical side wall portions to balance out the forces exerted by the current collector on the rail element. In an analogous manner, in embodiments with two electric conductors, they are advantageously also disposed on opposite vertical side wall portions.

The electric conductor(s) and ground conductor(s) are advantageously disposed in common groove(s) being vertically or laterally separated from each other in said common groove(s), i.e. a common groove may comprise both one or more electric conductors and one or more ground conductors. In alternative embodiments, the least one electrically conducting ground conductor is provided in at least one groove in the rail being separate from the at least one groove carrying the at least one electric conductor.

According to a second aspect of the invention, a method for electrical feeding of a road vehicle in a system according to the first aspect of the invention is provided. The method comprises connecting the at least one electric conductor to a source of electric power, connecting the at least one electrically conducting ground conductor to ground potential, and displacing the current collector vertically and/or laterally to connect mechanically and electrically with the at least one electric conductor and with the at least one ground conductor.

The features of the embodiments described above are combinable in any practically realizable way to form embodiments having combinations of these features. Further, all features and advantages of embodiments described above with reference to the first aspect of the invention may be applied in corresponding embodiments of the second aspect of the invention.

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 cross section view of an embodiment of a system according to the first aspect of the invention, fig. 2 shows a cross section view of parts of another embodiment of a system according to the first aspect of the invention, fig. 3 shows a cross section view of parts of yet another embodiment of a system according to the first aspect of the invention, fig. 4 shows a flow chart illustrating an embodiment of a method according to the second aspect of the invention, and fig. 5 shows a flow chart illustrating additional methods steps comprised in another embodiment of a method according to the second aspect of the invention.

DETAILED DESCRIPTION

Fig. 1 shows a cross section view of an embodiment of a system according to the first aspect of the invention. The system comprises an electrically propellable vehicle 2 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. The rail element 4 is further 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. From the cross section shown in fig. 1 , it is understood that the conductors 4a-d extend in the longitudinal direction of the rail element. The vehicle 2 is provided with a current collector 3 provided with contact elements 3a, 3b, 3c, 3d 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 sliding electrical and mechanical contact with a corresponding conductor 4a, 4b, while the ground contact elements 3c, 3d are configured to be brought in sliding 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 contact elements 3a, 3b make 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. In the same manner, the ground contact elements make contact with vertical wall portions of the ground conductors 4c, 4d.

The system furthermore comprises control means 6, such as an ECU, being in electrical contact with at least the ground contact elements 3c, 3d (as indicated by the dotted lines in the figure). The control means is configured to electrically disconnect the ground contact elements 3c, 3d from the vehicles’ chassis or body, measure electrical resistance between the ground contact elements, determine if the resistance is above a predetermined value and to provide, if the resistance is above said predetermined value, a warning signal indicating that the vehicle is not sufficiently grounded. The control means may furthermore be configured to send a control signal to the current collector, or to displacement means configured to co-act with the current collector, to displace the current collector to release the contact elements from contact with the electric conductors. The control signal is sent regardless of vehicle speed, i.e. electrical feeding of the vehicle is interrupted even at higher speeds if the vehicle is not sufficiently grounded. In other embodiments however, the control signal is sent only if the vehicle speed is below a predetermined level, for instance 20 km/h. The current collector is typically released from contact with the conductors by displacing the contact elements upwards/vertically by tilting the collector arms (holding the contact elements) backwards/upwards or by tilting the current collector as a whole backwards/upwards, as seen in the direction of travel.

The current collector is furthermore displaceable laterally. The movement of a current collector is described in detail in applicants’ earlier applications and will not be described in further detail here. Fig. 2 shows a cross section view of a rail element and a current collector of another embodiment of a system according to the first aspect of the invention. This embodiment differs from the embodiment in fig. 1 in that the rail element 14 and the current collector 13 are different. In this embodiment, the rail element is provided with a single ground conductor 14c arranged at the top of the rail element between the grooves 14’, 14”. A single ground contact element 13c of the current collector 13 is arranged in sliding electrical contact with the conductor 14c.

Fig. 3 shows a cross section view of a rail element and a current collector of yet another embodiment of a system according to the first aspect of the invention. This embodiment differs from the embodiment in figs. 1 and 2 in that the rail element 24 and the current collector 23 are different. In this embodiment, the rail element is provided with a third groove 24’” in which the ground conductors 24c, 24d are provided as one unit in the form of a U-shaped beam or profile at the bottom of the groove (in the same way as the electric conductors 4a, 4b in fig. 1 ). The current collector 23 is provided with two ground contact elements 23c, 23d arranged at the bottom end of corresponding collector arms. The contact elements are pressed laterally outwardly, i.e. in opposite directions, towards vertical side wall portions of the groove 24”’ to make contact with the corresponding ground conductor.

Fig. 4 shows a flow chart illustrating an embodiment of a method according to the second aspect of the invention. The method comprises connecting 31 the at least one electric conductor to a source of electric power, connecting 32 the at least one electrically conducting ground conductor to ground potential, and displacing 33 the current collector vertically and/or laterally to connect mechanically and electrically with the at least one electric conductor and with the at least one ground conductor, and propelling 34 the vehicle using electric power obtained from the rail element via the current collector.

Fig. 5 shows a flow chart illustrating additional methods steps comprised in another embodiment of a method according to the second aspect of the invention. The steps in fig. 5 taken alone may also be considered a method for determining ground contact in a system according to the first aspect of the invention having at least two ground conductors and ground contact elements. The method comprises disconnecting 41 the ground contact elements from electrical contact with the chassis and/or body portion of the vehicle, measuring 42 electrical resistance between the ground contact elements, determining 43 if the resistance is above a predetermined value, providing 44, if the resistance is above the predetermined value, a warning signal indicating that the vehicle is not sufficiently grounded, determining 45 a vehicle speed, sending 46, in response to the warning signal, a release control signal to the current collector if the vehicle speed is below a predetermined level such as 20 km/h, using, in response to the release control signal, the current collector (or means configured to co-act with the current collector, such as an actuator or motor) to release 47 the at least one contact element from contact with the at least one electrical conductor. The method steps illustrated in fig. 5 may be performed at predetermined intervals while the vehicle is driving, i.e. during step 34 as shown in fig. 4, or during standstill.

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. 1-3, and furthermore do not need to be recessed in the rail element as shown in the figures but may be arranged on the inner surface of the groove(s) and/or on top of the rail element. Furthermore, the ground contact element(s) do not need to form part of the current collector in the sense of a single unit which is connected and disconnected with the electric conductor(s) and ground conductor(s) together but may on the contrary be displaceable vertically and/or laterally separately from the contact element(s).