System for establishing an electrical connection between a power source and a motor vehicle, and contact device

Abstract

System for establishing an electrical connection between a power source (30) and an electrical circuit (40) in a motor vehicle with - a motor vehicle with several wheels (20) and at least one electrical circuit (40) and - a contact device (2 - 7) which is electrically connected or connectable to a power source (30), wherein - at least one of the wheels (20) has a rim (28) and a tire (21) located on the rim (28) made of electrically insulating material and one or more first contact elements (22 - 25) which are electrically connected or connectable to the at least one electrical circuit (40) of the motor vehicle, - the contact device (2 - 7) has one or more second contact elements (3 - 6) which are electrically connected or connectable to the power source (30), - the first and / or second contact elements (22 - 25; 3 - 6) are arranged and / or designed such that the first contact elements (22 - 25) come into contact with the second contact elements (3 - 6) and are electrically connected when the at least one wheel (20) of the motor vehicle rests against the contact device (2 - 7), and - the contact device is incorporated into a floor surface (1) which has a recess (2) adapted to the shape and size of the wheel (20) to be received, with a concavely curved surface on which the second contact elements (3 - 6) are provided, or the contact device has a ramp (7) arranged on a floor surface (1) which has a recess (2) adapted in shape and size to the wheel (20) with a concavely curved surface on which the second contact elements (3 - 6) are provided, characterized in that a first contact element (24) is lowered relative to a tread surface of the tire (21) by being offset radially inwards, so that the first contact element (24) has no contact with the ground during driving and can only be contacted by a correspondingly designed second contact element (3 - 6) of the contact device (2 - 7).

Description

[0001] The invention relates to a system for establishing an electrical connection between a power source and a motor vehicle, as well as a contact device according to the preamble of the independent claims.

[0002] Charging the batteries of electric or hybrid electric vehicles typically requires a cable connection between a charging station and the vehicle. Establishing this cable connection usually requires manual intervention. Furthermore, the charging cable can pose a tripping hazard.

[0003] From DE 42 36 286 A1, it is known to charge a vehicle battery by contactless energy transfer using an inductive transformer, the primary element of which is stationary and the secondary element of which is attached to the vehicle. Apart from the high costs of a corresponding charging infrastructure, the compensation of reactive power occurring in this process can be very complex. Furthermore, influences on the self- and mutual inductances of the coils required, for example due to temperature fluctuations, geometric position, and age-related drift, are difficult to control.

[0004] AT 507 541 A1 discloses a device for transmitting electric current to an electrically or hybrid-powered vehicle, comprising an electrically conductive roadway, electrically conductive tires, electrically conductive axles, electrically conductive current collectors and brushes, wherein these parts are installed in a multi-track vehicle and the wheels on one side are electrically insulated from the other side in order to be able to conduct different electrical potentials into the vehicle's electrical system, and by means of a roadway which has two or more separate electrically conductive wheel tracks which are embedded in an electrically insulated roadway substructure.

[0005] US 4,139,071 A discloses a roadway with a smooth surface for motor vehicles. Each electrified lane is equipped with at least two spaced-apart parallel electrical contact devices whose tops are flush with the roadway surface and positioned to make contact with a wheel on each side of the vehicle. The vehicle uses electrically conductive tires that roll on the electrically conductive surface of the contact devices. The vehicle also includes a battery to provide power for its operation when the wheels are not on the contact devices. The battery is charged by current drawn from the roadway during normal operation or by special charging pads while the vehicle is parked.

[0006] DE 10 2010 034 175 A1 discloses a device for the contactless transmission of energy to a vehicle, wherein a primary conductor can be arranged inductively coupled to a ring-shaped part of the vehicle, wherein the ring-shaped part is rotatably mounted on the vehicle, in particular on its frame, and wherein a secondary winding is arranged inductively coupled to the ring-shaped part on the vehicle.

[0007] The object of the invention is to provide a system and a contact device which enables the establishment of an electrical connection between a power source and the motor vehicle in a simple and safe manner.

[0008] This task is solved by the system and the contact device according to the independent claims.

[0009] The system according to the invention for establishing an electrical connection between a power source and an electrical circuit in a motor vehicle comprises a motor vehicle with several wheels and at least one electrical circuit, as well as a contact device that is electrically connected or connectable to a power source, and is characterized in that at least one of the wheels has one or more first contact elements that are electrically connected or connectable to the at least one circuit of the motor vehicle, the contact device has one or more second contact elements that are electrically connected or connectable to the power source, and the first and / or second contact elements are arranged and / or designed such that the first contact elements come into contact with the second contact elements and are thereby electrically connected.when at least one wheel of the motor vehicle is in contact with the contact device.

[0010] A motor vehicle has several wheels and at least one electrical circuit and is characterized in that at least one of the wheels has one or more first contact elements which are electrically connected or connectable to the at least one circuit in the motor vehicle and are arranged and / or designed on the at least one wheel in such a way that the first contact elements come into contact with one or more second contact elements of a contact device and are thereby electrically connected when the at least one wheel of the motor vehicle is in contact with the contact device.

[0011] The contact device according to the invention is electrically connected or connectable to a power source and has one or more second contact elements which are electrically connected or connectable to the power source and are arranged and / or designed such that they come into contact with one or more first contact elements provided on at least one wheel of a motor vehicle and are thereby electrically connected when the at least one wheel of the motor vehicle is in contact with the contact device.

[0012] A motor vehicle within the meaning of the present invention is preferably a land vehicle that is not permanently guided on tracks, in particular a road vehicle, for example a passenger car, truck, bus or motorcycle, which in particular has a hybrid or electric drive.

[0013] The invention is based on the approach of establishing an electrical connection between a power source located outside the motor vehicle and an electrical circuit located inside the motor vehicle, in particular a charging circuit for a battery, by moving one or more wheels of the motor vehicle, equipped with suitable electrical contact elements, towards a contact device also equipped with electrical contact elements and bringing them into contact with it, so that the contact elements of the contact device contact the corresponding contact elements on the respective wheel of the motor vehicle and thereby establish an electrical connection. The electrical contact elements located on the wheels are permanently connected to the electrical circuit in the motor vehicle or can be connected at least temporarily, for example by actuating a switch.The power source connected to the contact elements of the contact device is electrically connected to the vehicle's electrical circuit, particularly the battery charging circuit, when the contact elements on the relevant wheel touch the contact elements on the contact device. This can be easily achieved by driving the vehicle with the wheel(s) equipped with contact elements towards the contact device in such a way that the wheel rests on or against the device. This eliminates the need for manual intervention to establish the electrical connection between the power source and the vehicle's electrical circuit, or the use of an electrical charging cable. Furthermore, this method provides a particularly simple way to transmit electrical energy, especially compared to inductive transmission methods.

[0014] Overall, the invention thus allows for the simple and safe establishment of an electrical connection between a power source and a circuit located in a motor vehicle.

[0015] The at least one wheel has a rim and a tire mounted on the rim. The tire is manufactured using an electrically insulating material, such as plastic, rubber, or a rubber compound, for example, by applying a rubber compound to a substrate of textile and / or steel. In particular, the tread of the tire is substantially electrically insulating.

[0016] The first contact elements (one or more) are arranged on the tire. Establishing electrical contact between the second contact elements of the contact device and the first contact elements can be easily achieved by driving the vehicle or the relevant wheel towards the contact device until the first contact elements come into contact with the second contact elements.

[0017] In a further preferred embodiment, the rim is made of an electrically conductive material and the one or more first contact elements are connected to the rim. This represents a simple and particularly robust way of implementing electrically conductive second contact elements on the vehicle wheel.

[0018] The system preferably includes at least one battery designed to store electrical energy and connected, or connectable, to at least one electrical circuit. This at least one electrical circuit is therefore, in particular, a charging circuit. Preferably, the battery is connected to an electric motor for propelling the vehicle via a power circuit. Alternatively or additionally, it may also be provided that an electrical connection is established between the power source located outside the vehicle and the electric motor located inside the vehicle for propelling the vehicle by means of the first and second contact elements. Thus, the first and second contact elements on the wheel or on the contact device can establish not only a temporary electrical connection, e.g.,not only for charging purposes, but also to establish an essentially permanent electrical connection for the continuous transmission of electrical energy to the vehicle, in particular to the electric motor.

[0019] Furthermore, it is preferred that the contact device is arranged in the area of ​​a ground surface accessible to the motor vehicle, particularly in a stationary position. In this case, the motor vehicle or the relevant wheel can simply be driven up to the contact device until the first contact elements come into contact with the second contact elements. This makes it particularly easy to establish an electrical contact between the second contact elements of the contact device and the first contact elements.

[0020] According to one aspect of the invention, the contact device is integrated into the floor surface. For example, the floor surface can have a recess adapted to the shape and / or size of the wheel to be accommodated, in which the second contact elements are provided. According to an alternative aspect of the invention, however, the contact device can also have a ramp on which the second contact elements are provided. For example, the ramp is wedge-shaped, so that the vehicle or the wheel in question can drive onto the ramp via one leg of the wedge and exit the ramp again via a second leg. A recess is provided between the first and second legs of the ramp, in which the second contact elements are arranged.

[0021] Further features, advantages, and applications of the invention will become apparent from the following description in conjunction with the figures. The figures show: Fig. 1. A first example of a contact device in a cross-sectional view; Fig. 2 a second example of a contact device in a cross-sectional view; Fig. 3 a third example of a contact device in a cross-sectional view; Fig. 4 the third example of a contact device in overhead view; Fig. 5 a variant of the third example of a contact device in top view; Fig. 6 a fourth example of a contact device in a cross-sectional view; Fig. 7 a fifth example of a contact device in a cross-sectional view; Fig. 8 A first example of a motor vehicle wheel in a side view; Fig. 9 a second example of a motor vehicle wheel in a side view; Fig. 10 a third example of a motor vehicle wheel in a side view; Fig. 11 a fourth example of a motor vehicle wheel in a side view; Fig. 12 a first example of a wheel of a motor vehicle together with a contact device in a cross-sectional view; Fig. 13 an example with two wheels of a motor vehicle together with a contact device each in a highly schematic perspective representation; and Fig. 14 A second example of a wheel of a motor vehicle together with a contact device in a cross-sectional view.

[0022] Fig. Figure 1 shows a first example of a contact device in a cross-sectional view. The contact device has a trough-shaped recess 2 embedded in a base surface 1, the shape and / or dimensions of which are chosen such that a wheel 20 of a motor vehicle, shown here only schematically, can be received in the recess 2.

[0023] Preferably, the depth of the recess 2 is selected such that the vehicle can easily drive into and out of the recess 2 with its wheel 20. Preferably, the depth of the recess 2 is less than approximately 30% of the diameter of the wheel 20. On the other hand, the depth of the recess 2 is preferably selected such that the driver of the vehicle receives clearly perceptible haptic feedback when the wheel 20 enters the recess 2. Therefore, preferably, the depth of the recess 2 is greater than approximately 5% of the diameter of the wheel 20.

[0024] At least one electrical contact element 3 made of an electrically conductive material is provided on or attached to the surface of the recess 2 and is preferably adapted to the shape of the recess 2. In the example shown, the thickness of the contact element 3 is chosen to be relatively large in relation to the depth of the recess 2 for the sake of clarity. In principle, however, the contact element 3 can also be made considerably thinner. For example, the at least one contact element 3 could be one or more metal sheets attached to the recess 2.

[0025] Fig. Figure 2 shows a second example of a contact device. Unlike the one in Fig. In the first example shown, at least one contact element 3 is integrated into the recess 2, for example by being embedded in the recess 2, such that the surface of the contact element 3 is essentially flush with the concavely curved surface of the recess 2. Otherwise, the explanations relating to the first example apply accordingly to the second example.

[0026] Fig. Figure 3 shows a third example of a contact device in which several spaced-apart electrical contact elements 4 and 5 are provided in the trough-shaped recess 2 in the base surface 1. In the present example, these are integrated into the recess 2, as already explained above in connection with the second example. Alternatively, they can also be attached to or on the recess 2, as explained in connection with the first example.

[0027] Preferably, adjacent contact elements 4 and 5 are connected to the opposite poles (-) and (+) of a power source (not shown). For example, contact elements 5 can be electrically connected to the positive pole (+) of a power source and contact elements 4 to its negative pole (-). In the example shown, a total of three contact elements 4 connected to the negative pole and two contact elements 5 connected to the positive pole are depicted. However, it is also possible to connect an equal number of contact elements 4 and 5 to the negative and positive poles of the power source, respectively.

[0028] In the example shown, for clarity, a total of five contact elements 4 and 5 are depicted relatively large. However, it is also possible to provide the contact device with more than five contact elements 4 and 5 and / or to choose their dimensions to be smaller than shown. Conversely, it is also possible to provide fewer than five contact elements 4 and 5 and / or to choose their dimensions to be larger than shown. Furthermore, the preceding statements relating to the first and second examples of the contact device apply accordingly to this example.

[0029] Fig. Figure 4 shows the third example of the contact device in a top view. As can be seen from the illustration, the contact elements 4 and 5 are in this case strip-shaped and extend essentially in the axial direction of the trough-shaped recess 2.

[0030] Fig. 5 shows a variant of the one in the Fig. 3 and Fig. Figure 4 shows the third example of a contact device in which a plurality of electrical contact elements 6 are provided in the recess 2. In the present example, the contact elements 6 are arranged in three rows and five columns. However, it is also possible to arrange the contact elements 6 in more or fewer columns and / or more or fewer rows.

[0031] Analogous to the above explanations in connection with the in Fig. In the third example of the contact device shown in Figure 3, adjacent contact elements 6 can also be connected to the different poles of a power source in the present example. Depending on the application, however, it may also be preferable to connect the contact surfaces 6 to the different poles of the power source in a different way. For example, as indicated in the illustration, the contact elements 6 located in a column can be connected alternately to the positive and negative poles (+) and (-) of the power source. In the present example, the contact elements 6 of a first row are connected to the negative pole (-), the contact elements 6 of a second row to the negative pole (+), and the contact elements 6 of a third row again to the negative pole (-) of the power source. Alternatively or additionally, the contact elements 6 located in each row can also be connected alternately to the positive and negative poles of the power source.

[0032] Fig. Figure 6 shows a fourth example of a contact device in which the electrical contact elements 4 and 5 are arranged on or at the trough-like recess 2. Otherwise, the foregoing statements apply in connection with the [reference to be added]. Fig. 3 examples shown accordingly.

[0033] Fig. Figure 7 shows a fifth example of a contact device in which the recess 2 designed to receive a wheel is not integrated into the base surface 1, but into a wedge-shaped ramp 7. Preferably, the ramp 7 forms a separate unit that can be detachably attached to the base surface 1. This makes it possible to provide such a contact device with contact elements 4 and 5 provided in a recess 2 without great effort.

[0034] Fig. Figure 8 shows a first example of a wheel 20 of a motor vehicle in a side view. The tread of a tire 21, made of essentially electrically insulating material such as plastic or rubber, is visible. In particular, the tire 21 is a pneumatic tire, preferably tubeless, composed of natural and / or synthetic rubber, fillers such as carbon black or silica, plasticizers, oils and resins, as well as reinforcing materials such as steel, nylon, and cord.

[0035] The tread of the tire 21 is formed by its outer circumference, which is provided with electrical contact elements 22. These electrical contact elements 22 can be, for example, thin, electrically conductive metal sheets that are applied to or embedded in the tread of the tire 21. Alternatively or additionally, it is also possible to create electrically conductive contact surfaces 22 in the form of areas of the tread where, instead of a substantially electrically insulating tire material, a substantially electrically conductive tire material is used. This can be achieved, for example, by adding an electrically conductive component, such as a sufficient quantity of carbon black and / or metal particles, to the tire material in the areas of the tread intended for the contact elements 22 during the manufacturing process of the tire 21.In the example shown, the electrical contact elements 22 are designed as flat surfaces and each forms a continuous electrically conductive area. Alternatively, it is also possible to implement the contact elements 22 as a multitude of point-like or small-area electrically conductive elements distributed over a given area.

[0036] Fig. Figure 9 shows a second example of a wheel 20 in which an electrically conductive contact element 23 extends over the entire circumference of the tread of the tire 21. Preferably, the width of the contact element 23 is smaller than the width of the tire 21. It may also be preferred that the contact element 23 is arranged substantially in the region of the center of the circumference of the tire 21. Regarding the construction of the tire 21 and the implementation of the electrically conductive contact element 23, the preceding descriptions apply in connection with the one in Figure 9. Fig. 8 shown example accordingly.

[0037] Fig. Figure 10 shows a third example of a wheel 20 in which an electrically conductive contact element 24 is implemented in the form of a groove in the area of ​​the tread of the tire 21. Unlike the ones shown in the Fig. 8 and Fig. In the 9 examples shown, in which the contact surfaces 22 and 23 are provided in the area of ​​the surface of the respective tread, in the present example the contact element 24 is slightly lowered relative to the tread of the tire 21, i.e. offset radially inwards, so that it generally has no contact with the ground during normal driving operation and can only be contacted by a correspondingly designed contact element of the contact device (not shown).

[0038] Fig. Figure 11 shows a fourth example of a wheel 20 in which an electrically conductive contact element 25 is attached to the outer sidewall of the tire 21 and / or to the rim (not shown) of the wheel 20. In this embodiment as well, the diameter of the contact element 25, which circulates around the sidewall of the tire 21, is selected such that the contact element 25 is offset radially inwards relative to the tread surface to such an extent that it does not touch the ground during normal driving. Optionally, the contact element 25 can have an electrically insulating cover 26 on its side facing away from the tire 21.

[0039] The following section explains in more detail the interaction between the charging device and the wheel in establishing an electrical connection between a power source and an electrical circuit in the vehicle.

[0040] Fig. Figure 12 shows a cross-sectional view of a first example of a wheel 20 of a motor vehicle together with a contact device in

[0041] The form of a ramp 7 arranged on a floor surface 1, which has a recess 2 substantially adapted in shape and size to the wheel 20, in which an electrical contact element 3, for example in the form of a metal sheet, is provided. In the example shown, the wheel 20 is already in the recess 2, so that the contact element 23, which in this case is designed in the form of a circumferential electrically conductive surface (see Fig. 9) on the wheel 20 comes into contact with the contact element 3 in the recess 2, thus establishing an electrical contact between the contact elements 3 and 23. From the contact element 23 of the wheel 20, an electrical conductor 27 leads through the tire 21 and the rim 28 and / or a spoke (not shown) to the axle 29 and can from there be routed to the vehicle's electrical system via suitable electrical connections, for example via sliding contacts in the area of ​​the axle 29.

[0042] Fig. Figure 13 shows an example with two wheels of an axle of a motor vehicle, each with a contact device, in a highly schematic perspective view. In the example shown, the contact element 3a of the contact device in the foreground for the left wheel 20 of the vehicle is connected to the positive terminal (+) of a power source 30. The contact element 3b of the contact device in the background for the right wheel 20 of the vehicle, on the other hand, is electrically coupled to the negative terminal (-) of the power source 30.

[0043] As already mentioned in connection with the in Fig. As described in the example shown in Figure 12, the contact elements 23 located on the respective wheel 20 are in contact with the contact elements 3a or 3b of the contact devices when the wheels 20 are received in the respective recess 2, so that an electrical contact is established between the contact elements 3a or 3b on the one hand and the respective contact element 23 on the wheel 20 on the other hand.

[0044] An electrical conductor 27a or 27b, connected to the respective contact element 23 on the wheel 20, preferably runs through the tire 21 and through cavities in the rim 28 to the respective wheel hub. From there, it is routed by means of electrical conductors (dashed lines) through an axle, preferably designed as a hollow shaft 29, and from there to the positive terminal (+) or negative terminal (-) of an electrical circuit 40 in the vehicle. In this way, an electrical connection is established via the left wheel 20 between the positive terminal (+) of the power source 30 and the positive terminal (+) of the electrical circuit 40 in the vehicle, and an electrical connection is established via the right wheel 20 between the negative terminal (-) of the power source 30 and the negative terminal (-) of the electrical circuit 40 in the vehicle in a simple and robust manner.

[0045] Even though the power source 30 in the examples shown is a DC power source with a positive and a negative terminal, the invention can also be advantageously used to establish an electrical connection between an AC power source, e.g., an AC mains supply, and the vehicle's electrical system. The foregoing explanations apply accordingly, with one or more phases, the neutral conductor, or the grounding of the AC power source replacing the positive and negative terminals.

[0046] Fig. Figure 14 shows a second example of a wheel 20 together with a contact device in a cross-sectional view. In this case, the contact elements 4 and 5 of the contact device on the one hand and the contact elements 22 on the wheel 20 on the other hand are designed and / or arranged such that when the wheel 20 is received in the recess 2 of the contact device, a contact element of the wheel 20 comes into contact with a contact element 4 or 5 of the contact device.

[0047] Preferably, as with the one in Fig.In the example shown, adjacent contact elements 4 and 5 of the contact device are connected to the opposite poles (-) and (+) of the power source 30, respectively. Similarly, the corresponding contact elements 22 on the tire 20 are connected via different electrical conductors 27a and 27b to the negative pole (-) and positive pole (+) of an electrical circuit 40 of the vehicle's electrical system. Thus, only one wheel 20 is required to establish a complete electrical contact between the electrical circuit 40 located inside the vehicle and the power source 30 located outside the vehicle.

[0048] Preferably, the contact device can include a sensor device (not shown) configured to detect the presence of a wheel 20 and / or motor vehicle and / or contact between the contact device and the wheel, and only in this case connect the respective contact elements 3 to 6 of the contact device to the power source 30, whereas in the absence of the wheel, motor vehicle, or a defined electrical contact between the wheel and the contact device, the electrical contact elements 4 to 6 of the contact device remain disconnected from the power source 30. Preferably, a control device is provided for this purpose, which, depending on the signals supplied by the sensor device, actuates an electrical switch provided between the contact elements 3 to 6 on the one hand and the power source 30 on the other.This prevents, in a simple and reliable way, life-threatening voltages from being transmitted in the event of accidental contact with the electrical contact elements 3 to 6 of the contact device when no wheel or vehicle is at the contact device.

[0049] Although in the present examples the contact device has at least one trough-shaped recess 2 in which the contact elements 2 to 6 are provided, the latter can in principle also be provided on or at the substantially flat ground surface 1, which can be driven over by the vehicle, in particular by the at least one wheel 20 of the vehicle equipped with corresponding contact elements. The preceding descriptions of the electrical contacting of the contact elements 22 to 25 located on the wheel by the corresponding contact elements 3 to 6 of the contact device apply accordingly.

[0050] In principle, the invention allows the transfer of electrical energy from a power source 30 outside the motor vehicle to a circuit 40 located in the vehicle in the case of discontinuous operation, such as for the temporary charging of a battery located in the vehicle. Reference symbol list 1 floor area 2. In-depth study 3 - 6 contact elements (contact device) 3a, 3b contact elements (contact device) 20-inch wheel 21 tires 22 - 25 contact elements (wheel) 26 Cover 27, 27a, 27b electrical line 28 rim 29 Axle or hollow shaft 30 Power source 40 circuit

Claims

[1] System for establishing an electrical connection between a power source (30) and an electrical circuit (40) in a motor vehicle with - a motor vehicle with several wheels (20) and at least one electrical circuit (40) and - a contact device (2 - 7) which is electrically connected or connectable to a power source (30), wherein - at least one of the wheels (20) has a rim (28) and a tire (21) located on the rim (28) made of electrically insulating material and one or more first contact elements (22 - 25) which are electrically connected or connectable to the at least one electrical circuit (40) of the motor vehicle, - the contact device (2 - 7) has one or more second contact elements (3 - 6) which are electrically connected or connectable to the power source (30), - the first and / or second contact elements (22 - 25; 3 - 6) are arranged and / or designed such that the first contact elements (22 - 25) come into contact with the second contact elements (3 - 6) and are electrically connected when the at least one wheel (20) of the motor vehicle rests against the contact device (2 - 7), and - the contact device is incorporated into a base surface (1) which has a recess (2) adapted to the shape and size of the wheel (20) to be received, with a concavely curved surface on which the second contact elements (3 - 6) are provided, or the contact device has a ramp (7) arranged on a base surface (1) which has a recess (2) adapted in shape and size to the wheel (20) with a concavely curved surface on which the second contact elements (3 - 6) are provided, characterized by, that a first contact element (24) is lowered relative to a tread surface of the tire (21) by being offset radially inwards, so that the first contact element (24) does not have ground contact during driving and can only be contacted by a correspondingly designed second contact element (3 - 6) of the contact device (2 - 7). [2] System according to claim 1, wherein the rim (28) is made of an electrically conductive material and the one or more first contact elements (22 - 25) are connected to the rim (28). [3] System according to one of the preceding claims comprising at least one battery designed for storing electrical energy and connected or connectable to at least one electrical circuit (40). [4] System according to one of the preceding claims, wherein the ramp (7) is wedge-shaped, so that the vehicle or the wheel (20) in question can drive onto the ramp (7) via one leg of the wedge and can leave the ramp (7) via a second leg. [5] System according to claim 4, wherein the recess (2) in which the second contact elements (3 - 6) are arranged is provided between the first and second leg of the ramp (7). [6] System according to one of the preceding claims, wherein the depth of the depression (2) - is less than 30% of the diameter of the wheel (20) and / or - is greater than 5% of the diameter of the wheel (20) and / or - is chosen so that the driver of the motor vehicle receives a clearly perceptible haptic feedback about the wheel (20) entering the recess (2). [7] System according to one of the preceding claims, wherein the contact device (2 - 7) has a sensor device configured to detect the presence of a wheel (20) and / or motor vehicle and / or contact between contact device (2 - 7) and wheel (20) and only in this case connect the respective contact elements (3 - 6) of the contact device (2 - 7) to the power source (30), whereas in the absence of the wheel (20), motor vehicle or a defined electrical contact between wheel (20) and contact device (2 - 7) the electrical contact elements (3 - 6) of the contact device (2 - 7) remain disconnected from the power source (30). [8] Contact device (2-7) for use in a system according to one of claims 1 to 7, wherein the contact device (2-7) is electrically connected or connectable to a power source (30) and has one or more second contact elements (3-6) which are electrically connected or connectable to the power source (30) and are arranged and / or designed such that they come into contact with and are electrically connected to one or more first contact elements (22-25) provided on at least one wheel (20), which has a rim (28) and a tire (21) made of electrically insulating material located on the rim (28) of a motor vehicle, when the at least one wheel (20) of the motor vehicle is in contact with the contact device (2-7), and the contact device is installed in a floor surface (1).which has a recess (2) adapted to the shape and size of the wheel (20) to be received, with a concavely curved surface on which the second contact elements (3-6) are provided, or the contact device has a ramp (7) arranged on a base surface (1), which has a recess (2) adapted in shape and size to the wheel (20) with a concavely curved surface on which the second contact elements (3-6) are provided, wherein a second contact element (3-6) of the contact device (2-7) is designed in accordance with a first contact element (24), , characterized by , that the first contact element (24) is lowered relative to a tread surface of the tire (21) by being offset radially inwards, so that the first contact element (24) does not have ground contact during driving and can only be contacted by the correspondingly designed second contact element (3 - 6) of the contact device (2 - 7).

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