Patent Description:
One limiting factor in charging cables for electric vehicles is the heat that is generated when high currents flow through the cable and the electrical connector from the charging station to the battery of a vehicle. The heat may be actively conducted away from the heat sources using liquids. In this way current rates over <NUM> A are achieved. For this kind of cooling arrangements are required that comprise and conduct the liquid from heat sinks to the heat sources and back. Additional devices such as pumps are necessary.

Prior art <CIT> discloses an electrical contact element for a car charging plug connector. The electrical contact element has a contact part and a connection part, wherein the connection part can be connected to an electrical conductor of a cable. Cooling liquid can be delivered to the contact element. As a result, the heat produced on the contact element is extracted directly.

<CIT> relates to a connection unit for a fluid-cooled cable and to a system composed of a plug-in connector, a fluid-cooled cable and a connection unit. The connection unit comprising a housing, which has a cable connecting opening, a fluid inlet opening and a fluid outlet opening.

<CIT> relates to a plug-in connector part for plug-in connection to a mating plug-in connector part.

Prior art <CIT> discloses a charging cable for transferring electrical energy to an energy storage device of an electric or hybrid vehicle. The charging cable comprises a coolant-guiding device, which is arranged inside a cable jacket.

An objective of the invention may be to provide an electric vehicle charging system, with which high current rates are possible.

The problem is solved by an electric vehicle charging system, having the features of claim <NUM>. Advantageous embodiments of the invention are specified in the dependent claims.

According to the invention, an electric vehicle charging system comprising a charging connector configured to receive a charging cable. The charging cable and/or the charging connector provide means for guiding a coolant, cooling the charging cable and/or the charging connector. The electric vehicle charging system further comprises a thermal management unit for cooling the coolant. The thermal management unit comprises a vapour-compression refrigeration system (VCRS) for cooling the coolant below ambient temperature.

The charging connector provides the charging current from a charging station to the battery of an electric vehicle. Thus, "charging connector" is understood to be a handheld device such as a charging gun or charging nozzle. The counterpart of the charging connector on vehicle-side is called socket. For charging the vehicle, the charging connector provides a charging cable. In the charging cable at least charging wires for conducting the electrical current to the vehicle are arranged. A means for guiding a coolant thereby preferably is a cooling cable or cooling line in which the coolant is flowing. However, also other means for guiding the coolant are possible. The coolant could be any fluid with which a cooling effect to the cable in particular the charging wires in the cable and/or the connector, respectively the electric contacts of the connector, is achieved.

The term thermal management unit has to be understood comprising all parts, which are used for cooling the coolant. According to the invention the thermal management unit at least comprises a vapour-compression refrigeration system. Such a system uses a refrigerant, wherein the refrigerant undergoes a phase change so that a temperature below ambient temperature is achieved. In contrast to a coolant, which is cooled to a temperature close to the ambient temperature the use of a vapour-compression refrigeration system results to a higher cooling effect of the connector and/or the cable. Accordingly, the vehicle can be charged with a higher electric current, without exceeding a temperature limit of the vehicle charging system.

As the heat loss in the cable increases with a reduced cross section of the wires and an increased length of the cable, with this invention it is possible reducing the cross section of the cable and/or using a longer cable. Further, by using a vapour-compression refrigeration system the vehicle charging system also can be used in regions with high ambient temperature like e.g. in the desert. Especially in these areas, a common air-cooled heat exchanger has a low cooling effect on the coolant. Usability of the vehicle charging system therefore is improved.

In a preferred embodiment of the invention, the coolant is a refrigerant of the vapour-compression refrigeration system with which the charging cable and/or the charging connector is cooled. The refrigerant therefore is directly used for cooling the components of the vehicle charging system. Accordingly, no further circuit is used for cooling the components. Thus, the number of components are reduced. A respective vehicle charging system can be economically provided. As the refrigerant is directly evaporated in the cooling cable, the heat transfer is improved.

In a further preferred embodiment of the invention, the vapour-compression refrigeration system comprises an expansion valve for expanding the refrigerant, arranged in the charging connector. In other words, the refrigerant is provided as compressed fluid to the charging connector. By using this configuration the refrigerant is directly expanded in the charging connector, so that the charging connector respectively the electrical contacts can be cooled with a maximum cooling efficiency.

Alternatively, the vapour-compression refrigeration system comprises an expansion valve for expanding the refrigerant, arranged in a charging station of the electric vehicle charging system. The charging station thereby is a stationary part of the vehicle charging system. In this charging station, usually most of the components are accommodated. Preferably, also the vapour-compression refrigeration system is arranged in the charging station. With this arrangement, the charging connector could be provided smaller compared to the configuration where the expansion valve is arranged in the charging connector. Maintenance of the expansion valve is improved.

Advantageously, a refrigeration cycle of the vapour-compression refrigeration system is provided separate to a cooling cycle of the coolant, wherein an interconnecting heat exchanger is arranged between both cycles for removing heat of the coolant. In this configuration two independent cycles are provided, which are merely thermally connected to each other via the interconnecting heat exchanger. Preferably, the interconnecting heat exchanger is a counterflow heat exchanger. As both cycles are independent from each other the coolant and the refrigerant can be freely chosen without boundary conditions of the other cycle. Accordingly, the coolant and the refrigerant can be selected to have a maximum efficiency.

In a further advantageous development, the thermal management system comprises the vapour-compression refrigeration system for cooling the coolant provided to the charging connector, and an air-cooled heat exchanger for cooling the coolant provided to the charging cable. The thermal management system therefore comprises two totally independent cooling systems. One of these cooling systems cools the electric contacts wherein the other cooling systems cools the electric wires in the cable. Each of the cooling systems has a separate cooling line, so that two cooling loops are provided.

Using two separate cooling systems has the advantage, that each system can be optimized to the component to be cooled, so that the electric contacts gets the coolant having a much lower temperature as the cable.

As the electrical contacts are already cooled by the other cooling system, it is not necessary to have a separate cooling line directly to the electrical contacts for providing the contacts with the coolest coolant. Therefore, the cooling loop of the cable preferably is arranged that the coolant supply is through one of the poles, while a coolant return is through the other pole. The cooling loop thereby is simplified.

Preferably, the thermal management unit comprises an air-precooling heat exchanger for precooling of the coolant arranged upstream to the interconnecting heat exchanger and between the refrigeration cycle and the cooling cycle of the coolant. The air-precooling heat exchanger thereby exchanges the heat of the coolant to the ambient air. With the air-precooling heat exchanger, the coolant is cooled before it enters the interconnecting heat exchanger. As the temperature of the coolant entering the interconnecting heat exchanger is already lowered, the compressor stage of the refrigeration cycle can be dimensioned much smaller.

As cooling of the coolant is provided with the air-precooling heat exchanger it is not necessary running the refrigeration cycle the whole time. The refrigeration cycle therefore can be switched on when required. The energy consumption of the vehicle charging system can be reduced. In addition, if the refrigeration cycle has a failure, the charging system still can be operated at least on a reduced current rate. Such an arrangement therefore is fail safe.

In an advantage embodiment, the same air-cooled heat exchanger is used for precooling the coolant and for cooling the compressed refrigerant of the refrigeration cycle. In other words, merely one heat exchanger is necessary for cooling the coolant and the refrigerant. The components therefore can be reduced, so that such a vehicle charging system is more economically.

These and other features, aspects and advantages of the present invention will become better understood with reference to the accompanying figure and the following description.

The subject matter of the Invention will be explained in more details in the following description illustrated in the drawings, showing in:.

<FIG> shows an electric vehicle charging system <NUM> according to a first embodiment of the present invention. Such an electric charging system <NUM> comprises a charging connector <NUM>, which has to be connected to a socket (not shown) of an electric vehicle for charging the battery. The charging connector <NUM> is connected with a charging cable <NUM>, extending from a charging station <NUM>. In the charging station <NUM>, a thermal management unit <NUM> is provided. According to the invention, the thermal management unit <NUM> comprises a vapour-compression refrigeration system <NUM> providing a refrigeration cycle <NUM>. The vapour-compression refrigeration system <NUM> comprises a compressor <NUM> for compressing a refrigerant. An air-cooled heat exchanger <NUM> is arranged downstream to the compressor <NUM> for cooling the compressed refrigerant.

An expansion valve <NUM> is arranged next to the air-cooled heat exchanger <NUM>. With the expansion valve <NUM>, the refrigerant is expanded, so that the temperature of the refrigerant is decrease below ambient temperature. The thermal management unit <NUM> in the charging station <NUM> is connected to coolant lines <NUM> provided in the charging cable <NUM>, so that the refrigerant is transported through the coolant lines <NUM>. In the shown embodiment, the coolant lines <NUM> merely cool the charging cable <NUM> of the vehicle charging system <NUM>. The coolant lines <NUM> therefore do not extend into the charging connector <NUM> for cooling electrical contacts <NUM> of the charging connector <NUM>.

In <FIG>, an electric vehicle charging system <NUM> according to a second embodiment of the present invention is shown. The second embodiment differs to the first embodiment shown in <FIG> by the features that additionally to a refrigeration cycle <NUM> of the vapour-compression refrigeration system <NUM>, a cooling cycle <NUM> of the coolant is arranged in the charging station <NUM>. The coolant cycle <NUM> in this embodiment comprises an air-precooling heat exchanger <NUM> for precooling the coolant medium. An interconnecting heat exchanger <NUM> is arranged downstream to the air-precooling heat exchanger <NUM>. The interconnecting heat exchanger <NUM> is arranged between the cooling cycle <NUM> of the coolant and the refrigeration cycle <NUM>. By means of the interconnecting heat exchanger <NUM>, heat of the coolant is transferred to the refrigerant of the refrigeration cycle <NUM>, so that the coolant is cooled.

After the interconnecting heat exchanger <NUM>, the coolant is transported to a coolant tank <NUM>, where the coolant is stored. A coolant pump <NUM> is arranged downstream to the coolant tank <NUM>. From the coolant pump <NUM>, the coolant is pumped to the coolant lines <NUM>. In this embodiment, the coolant lines <NUM> are provide in the charging cable <NUM> and the charging connector <NUM> for cooling the charging cable <NUM> and the electrical contacts <NUM> in the charging connector <NUM>.

Additionally to the interconnecting heat exchanger <NUM>, the refrigeration cycle <NUM> comprises downstream to the interconnecting heat exchanger <NUM> the compressor <NUM> for compressing the refrigerant. The air-cooled heat exchanger <NUM>, is arranged after the compressor <NUM> for cooling the refrigerant. Upstream to the interconnecting heat exchanger <NUM> the expansion valve <NUM> is provided for expanding the refrigerant in the refrigeration cycle <NUM>.

In a further embodiment, not shown in the figures, the air-precooling heat exchanger <NUM> provided in the cooling cycle <NUM> for precooling the coolant is omitted.

Claim 1:
Electric vehicle charging system (<NUM>) comprising a charging connector (<NUM>) configured to receive a charging cable (<NUM>), wherein the charging cable (<NUM>) and/or the charging connector (<NUM>) provide means (<NUM>) for guiding a coolant, cooling the charging cable (<NUM>) and/or the charging connector (<NUM>), and a thermal management unit (<NUM>) for cooling the coolant,
wherein the thermal management unit (<NUM>) comprises a vapour-compression refrigeration system (<NUM>) for cooling the coolant below ambient temperature,
characterized in that,
the vapour-compression refrigeration system (<NUM>) comprises an expansion valve (<NUM>) for expanding the refrigerant, arranged in the charging connector (<NUM>), and that the coolant cools electric contacts (<NUM>) of the connector (<NUM>).