Patent Description:
For high power charging of electric vehicles, EVs, typically a liquid cooled charging arrangement is used to provide adequate heat removal during charging. Such a charging arrangement generally comprises a charging cable, including a plurality of conductors and a charging connector, wherein power contacts are located.

The cable itself comprises multiple conductors, specifically three conductors per DC polarity and additionally one conductor providing a ground connection. The conductors are insulated to prevent mutual contact of conductive parts. For dielectric or mechanical reasons the charging cable may comprise additional parts.

To remove heat generated by Joule effect both in the charging cable and in the charging connector, it is known to provide a cooling by guiding a flow of cooling liquid from a cooling unit, typically located inside or outside a charge post, through the charging cable and the connector back to the cooling unit, where the heat provided to the coolant by Joule effect is preferably dissipated to the surrounding ambient air or alternatively for example to cooling water, to a refrigeration circuit, or to external heat load as waste heat utilization. For this reason, in a known charging cable the conductors are arranged in an inner part of the cable, which inner part provides a first cooling channel for the cooling fluid. The inner part is enclosed by a tight sheath. On the outer side of the sheath the charging cable comprises a second channel for the cooling fluid, which second channel again is enclosed by a sheath surrounding the entire cable. The flow of the cooling fluid is primarily assumed to be directed so that the outer fluid space is used for the fluid to flow from a charging post towards the end connector, and back through the inner fluid volume. However, an opposite orientation of the fluid flow generally may also be provided.

Such liquid cooling is necessary for high-current fast EV chargers, mainly because the liquid cooling avoids other necessary use of bulky charging conductors which would make the charging cable very difficult to handle. Furthermore, the liquid cooling in the charging cable must be designed to meet the clause reported in standard IEC <NUM>-<NUM>, which limits temperature rise of electrical terminals in the charging connector to <NUM> maximum.

For example, <CIT> discloses a heavy-current charging cable which has an outer jacket, a number of heavy current cores which extend in the longitudinal direction, and at least one cooling jacket with at least one hollow chamber extending in the longitudinal direction for conducting a coolant.

<CIT> discloses a vehicle conductor for use with an electric automobile, comprising a protection pipe, including at least one wire in the protection pipe capable of supplying power, and a cooling pipe positioned proximate the at least one wire in the protection pipe.

In a liquid cooled charging cable, within a common charging cable length range from <NUM> to <NUM>, the contact resistance between the power contacts of the charging cable's connector and mating contacts in a car socket is typically a few percent of the ohmic resistance of the conductors. Hence, when charging an EV at <NUM> A, heat generated in each power contact of the charging connector is negligible as compared to the total heat generated through the conductors' length. Nevertheless, in prior art, for cost-effectiveness reasons, geometry of the power contacts did not change in low power charging cables such as up to <NUM> A and in high power charging cables such as up to <NUM> A as of today. When charging an EV at <NUM> A, even in a cooled charging cable, a very high temperature gradient between <NUM> and <NUM> is expected along the power contacts in the charging connector.

Moreover, in existing solutions, the power contacts are electrically connected to the conductors through a very small area, for example crimped, and the coolant path surrounds or is embedded within that small area. This means that, in existing configurations, when charging at high currents, a very large heat flux, i.e. heat load divided by area, must be removed from the power contacts. As a consequence, there is a need for cooling not only the charging cable, but also the charging connector.

In this regard <CIT> discloses a charging connector which has at least one liquid cooled power contact arranged in a charging connector housing. The liquid cooled power contact has a first connection area, accessible via a contact side of the charging connector housing, for direct electrical connection to an electrical power recipient and a second connection area directly electrically connected to a charging cable. The connector additionally has at least one charging cable cooling device that is fluid-connected to a cooling fluid line. The charging connector has a bypass supply line and a bypass return line fluid-connected thereto. The bypass supply line and the bypass return line are respectively fluid-connected to the cooling fluid line, so that a stream of cooling fluid from the cooling fluid line via the bypass supply line to the bypass return line back to the cooling fluid line is made possible. The bypass ports allow the flow into a power contacts cooling device.

<CIT> discloses a vehicle connector plug wherein cooling devices in form of a refrigerator and coolant pipes are thermally coupled with the plug for cooling a portion of the plug. The cooling devices are closed when separated from the plug. The plug has a coupling portion and a handle portion. The cooling devices comprise channels that are guided through the handle portion. The cable is held at partially tube-like channels of the cooling devices by a common cover.

<CIT> discloses an electrically conductive contact element for an electrical plug connector, which contact element comprises a cooling cavity having a distal opening to be fluidic connected to a distal opening of a radially inner tube of a charging cable.

Document <CIT> relates to a cable assembly with a temperature regulating means.

Document <CIT> relates to a cable head of a high-current multiple cable for use in direct-current applications, in which the ends of the cable cores are inserted into bore holes extending concentrically with respect to the axis of a cylindrical section of a cable lug. A central cooling-water channel is provided in the center of the cable lug.

Document <CIT> relates to a charging plug comprising a cooling mechanism for the charging cables.

Document <CIT> relates to an electrically conductive contact element for an electric plug connector.

A drawback of prior art liquid cooled charging connectors is an insufficient thermal performance of the cooling system.

It is therefore an object of the invention to provide a charging connector for charging an electrical vehicle that overcomes the drawbacks explained before, in particular to provide a charging connector which topologically matches the charging cable described in this document and enables an appropriate dielectric design and the required electric properties. Additionally, the invention should provide a suitable, ideally very good, cooling of the cable and the connector itself, ensuring that the temperature of the charging connector and its contacts meets the requirements, as well as good manufacturability, reasonable price, weight, reliability and other operation properties.

The object of the invention is solved by the features of the independent claims. Preferred embodiments are detailed in the dependent claims.

Thus, the object is solved by liquid cooled cable arrangement for high-power fast charging of electric vehicles, comprising.

wherein the first connecting element and the second connecting element each are thermally connected to the inner channel and the outer channel of the charging cable, such that heat generated in the contacts during charging can be removed by the liquid coolant.

Therefore it is a key point of the invention that a maximum operating temperature of the contact elements is reduced as compared to existing solutions known from prior art. In the charging connector by said first connecting element and said second connecting element a heat transfer area between the contacts and the coolant fluid is increased and removal of heat from the contact elements advantageously can be maximized. In result, said first and second connecting elements each act as a very effective heat sink, removing heat energy form the contact elements and guiding the heat very effectively to the coolant fluid. The contacts, also referred to as power contacts, are for this purpose not directly electrically connected to the conductors but rather indirectly through the first and the second connecting elements, provided for example as metal blocks. The first and the second connecting elements are preferably made by copper or aluminium. Thus, use of first and the second connecting elements enhances the heat transfer area between the contacts and the coolant, thereby allowing higher current rates such as 600A that could be considered in future standards for liquid cooled charging cables. The solution advantageously reduces contacts resistance and thermal losses, while durability of the contacts over time is increased. Lower temperature also leads to the use of a more reliable, compact and cost-effective cooling unit in a charge post, such as an EVSE, while complying with present limitation imposed by IEC <NUM> standard on the maximum temperature rise of electrical terminals/contacts in a charging cable's charging connector.

The proposed solution for reducing the maximum temperature on the contacts is beneficial for in particular three main reasons. First, since electrical resistance of the contacts increase with temperature, a lower temperature of the contacts implies lower thermal losses due to Joule effect. Second, a lower maximum working temperature increases the reliability and durability of the contacts, which must survive a high number of mating cycles. The higher the maximum working temperature, the softer the copper of the contacts becomes over time. If the material of the contacts becomes softer, their elastic behaviour is affected, and the contact provided with pins of an electric vehicle socket during charging becomes weaker. This in turns increases the electrical resistance and the thermal losses. Third, no performance derating is needed at high ambient air temperature.

The liquid cooled cable arrangement can be used as part of an electric vehicle supply equipment, EVSE, also referred to as electric vehicle, EV, charging station, electric recharging point, charging point, charge point, charge post or electronic charging station, ECS. The EVSE is an element in an infrastructure that supplies electric energy for recharging of electric vehicles, including electric cars, neighbourhood electric vehicles and plug-in hybrids. EVSEs usually comply with standards for electric vehicle fast charging, such as the so-called Combined Charging System, CCS, protocol according to IEC <NUM>-<NUM> and SAE J1772 standard for charging electric vehicles both in the US and in the European Union, EU. The Combined Charging System, CCS, protocol is a fast charging method for charging electric vehicles delivering high-voltage direct current via a charging connector derived from SAE J1772 standard (IEC Type <NUM>) or IEC Type <NUM> connector. Automobile manufactures that support CCS include Jaguar, Volkswagen, General Motors, BMW, Daimler, Ford, FCA, Tesla and Hyundai. The CSS standard is controlled by the so called CharIN consortium. Besides other protocols such as, for example, CHAdeMO, as abbreviation of CHArge de Move, or GB/T, in particular according to <NUM>-<NUM> standard. The proposed solution can be advantageously used with even higher charging currents such as more than 500A or 600A and/or in combination with newer standards not yet defined requiring higher currents. Numerical analysis on thermal performance of the proposed arrangement showed that a maximum temperature rise of the contacts, which are also referred to as power contact elements, during a charge session at 500A to <NUM> A is below <NUM> in an ambient temperature range from -<NUM> to +<NUM>. With low viscosity synthetic fluids as cooling liquids, in the foreseen flow rate range, the maximum pressure drop in the charging connector is around <NUM> or even below <NUM>,<NUM> bar.

According to a preferred implementation, the first connecting element and the second connecting element each comprise fluid channels fluidically connecting the inner fluid channel and the outer fluid channel of the charging cable, such that heat generated in the contacts during charging can be removed by the liquid coolant. The fluid channels of the first connecting element and/or the second connecting element are preferably connected to the outer fluid channel and/or the inner fluid channel by means of gluing, through push-in fittings and/ or compression fittings. The fluid channels of the first connecting element and/or the second connecting element preferably are machined, which does not provide a significant cost addition for manufacture, as generally the contact elements require machining. Alternatively, the first connecting element and the second connecting element may each be 3D-printed, which is an advantageous solution if they are to be manufactured with complex internal channels for a very efficient heat transfer. The same applies to the contact elements.

According to a preferred implementation, the first connecting element and the second connecting element each comprise a charging cable mating part for connection with the charging cable and a contact element mating part for connection with the concerning contact element, wherein the contact element mating part has a wider radial extension than the charging cable mating part. Further, the mating parts may each be in essentially half-cylindrical formed. By providing the contact element mating part with a large radial extension, there is a large surface area available for heat transfer from the contact elements to the connecting elements.

In a further preferred implementation, the fluid channels in the first connecting element and/or the second connecting element each consist of an axial channel part and a radial channel part. The axial channel part preferably is open towards an axial surface of the connecting element. The radial channel part preferably is open towards a radial surface of the connecting element. Additionally, the axial channel part and the radial channel part are fluidically connected to each other. By providing such channel geometry the surface / part / section of the connecting element contacting the electric contact to be cooled very effectively.

According to a preferred implementation, the liquid cooled cable arrangement further comprises an insulating casing, which houses the first connecting element and the second connecting element. The insulating casing electrically insulates said connecting elements from each other. Additionally, the insulating casing may also house the positive contact element and/or the negative contact element. It also may electrically insulate said contact elements from each other. The insulating casing optionally may provide a connector housing insulating the connector from the surrounding.

According to a further implementation, a gap is formed between the insulating casing and each connecting element. Said gap preferably forms a fluid channel fluidically connecting the radial channel parts with the outer fluid channel of the charging cable. Alternatively, instead of a gap there may be provided a number of fluid channels or fluid grooves in the insulating casing that connect the radial channel parts with the outer fluid channel of the charging cable. By such a design the area of the connecting element which is cooled by the trough flowing coolant fluid advantageously can be very large.

The insulating casing particularly may be injection molded. It may be designed monolithically or it may consist of a plurality of distinct casing parts that are assembled to provide the connector housing. The insulating housing may be assembled with the other parts of the connector, in particular with its conducting parts as for example the first and/or the second connecting elements and/or the contacts. Alternatively, the insulating casing can be cast around or molded around the first connector element and/or the second connector element.

A very safe and simple way of electrically insulating the current leading elements of the connector can be achieved by providing the liquid coolant as a dielectric fluid.

In one implementation the outer fluid channel of the charging cable provides a flow of coolant liquid from the charging station to the connector, specifically to the fluid channels provided in the first connecting element and in the second connecting element, and the inner fluid channel of the charging cable provides a flow of coolant liquid from the connector, specifically from the fluid channels of the first and the second connecting elements, back to the charging station. This ensures that the outside of the charging cable as well as the outside of the connector are at a low temperature, as they are in contact with fresh coolant liquid coming from the charging station, such that even under high loads a user can touch and handle the cable and the connector very comfortably. Additionally, the charging cable may comprise an outer layer of soft material for protection at very low temperatures.

The positive conductors and/or the negative conductors may be crimped and/or welded or soldered to the concerning connecting element. Additionally or alternatively, the contact elements may be connected to the concerning connecting element by a push-in mechanism, by screwing and/or by welding or soldering or brazing and/or by gluing.

The contacts may comprise pockets for thermocouples, pockets for contact springs close to tips of the contacts and/or stress relief openings at joints between different contacts and/or cooling channels connected to the fluid channels. The connecting elements may be directly or indirectly connected with the contact. Alternatively, the contacts and the connecting elements may be monolithically formed, in particular as a single block of copper.

The object is further solved by a method for liquid cooling a charging connector connected to a liquid cooled charging cable for high-power fast charging of electric vehicles, whereby.

The proposed method allows for advantageously reducing a maximum temperature on the contacts such that higher charging current can be used for charging the electric vehicle.

In a preferred implementation of the method, the first connecting element and the second connecting element each comprise fluid channels fluidically connecting the inner fluid channel and the outer fluid channel of the charging cable, comprising the step of conveying liquid coolant through the fluid channels of the first connecting element and the second connecting element for removing heat generated during charging in the contacts.

In a further preferred implementation of the method a gap is formed between the insulating casing and each connecting element, comprising the step of conveying liquid coolant through the gap for removing heat generated during charging in the contacts.

Further embodiments and advantages of the method are directly and unambiguously derived by the person skilled in the art from the system as described before.

<FIG> shows a part of a liquid cooled cable arrangement according to a preferred implementation in a schematic sectional view along the longitudinal axis for high-power fast charging of electric vehicles. The arrangement comprises a charging connector <NUM> and a liquid cooled charging cable <NUM>. <FIG> shows a sectional view through the liquid cooled charging cable <NUM> in a direction orthogonal to the longitudinal axis of the cable <NUM>. The liquid cooled charging cable <NUM> comprises three positive conductors <NUM> and three negative conductors <NUM> for supplying charging current. It further comprises an insulated ground line <NUM>, which is arranged in the middle of the section of the charging cable <NUM>. The positive conductors <NUM>, the negative conductors <NUM> and the ground line <NUM> are each individually insulated to prevent mutual contact.

The charging cable further comprises an inner fluid channel <NUM> and an outer fluid channel <NUM> surrounding the inner fluid channel <NUM>. The inner fluid channel <NUM> and the outer fluid channel <NUM> together provide a supply path <NUM> and a return path <NUM> for a liquid coolant. The inner fluid channel <NUM> is enclosed by a tight sheath <NUM>, which at the same time divides the inner fluid channel <NUM> from the outer fluid channel <NUM>. The outer fluid channel <NUM> again is enclosed by an outer sheath <NUM> surrounding the entire cable <NUM>. The three positive conductors <NUM>, the three negative conductors <NUM> and the ground line <NUM> are each arranged within the inner fluid channel <NUM>. The ground line <NUM> connection is not dealt with in detailed in this disclosure, as the charging cable <NUM> fits to a standardized connector layout.

The charging connector <NUM> comprises a positive contact <NUM>, a first connecting element <NUM>, a negative contact <NUM> and a second connecting element <NUM> for connecting to respective socket of an electric vehicle, not shown. The positive contact <NUM> is electrically connected to the positive conductors <NUM> by the first connecting element <NUM>. The negative contact <NUM> is electrically connected to the negative conductors <NUM> by the second connecting element <NUM>. The first connecting element <NUM> and the second connecting element <NUM> each are copper blocks. The connection between the positive conductors <NUM> / negative conductors <NUM> and the first connecting element <NUM> / second connecting element <NUM> needs to be reliable, but does not present high electric insulation requirements since the conductors <NUM>, <NUM> insulation prevents electrical contact of the positive and the negative conductors <NUM>, <NUM>. Since at the respective connection to the copper blocks of the first connecting element <NUM> and the second connecting element <NUM>, respectively, the conductors <NUM>,<NUM> position is fixed, touching of the conductors <NUM>, <NUM> is prevented in the area. The space for connection (e.g. soldered) can be formed inside of the copper blocks of the first connecting element <NUM> and the second connecting element <NUM> themselves.

The first connecting element <NUM> and the second connecting element <NUM> each are embodied / arranged in an electrically insulating casing <NUM>. The insulating casing <NUM> prevents accessibility of the live parts, i.e. to those parts energized during charging, from outside. Further, the insulating casing <NUM> provides an insulating separation of the first connecting element <NUM> and the second connecting element <NUM> by an insulating wall <NUM> arranged in between. This separation, i.e. the creepage distance between the first and the second connecting elements <NUM>, <NUM> advantageously is as large as possible.

The first connecting element <NUM> and the second connecting element <NUM> are identically formed, such that the following description of the first connecting element <NUM> also is applicable to the second connecting element <NUM>. The first connecting element <NUM> consist of a charging cable mating part <NUM> for connection with the charging cable <NUM> and a contact mating part <NUM> for connection with the concerning contact <NUM>, <NUM>. It further comprises fluid channels <NUM>, which fluidically connect the inner fluid channel <NUM> and the outer fluid channel <NUM> of the charging cable <NUM>. Each fluid channel <NUM> comprises an axial channel part <NUM> and a radial channel part <NUM>. Each axial channel part <NUM> is open towards an axial surface <NUM> of the connecting element <NUM> located at its charging cable mating part <NUM>. Further, each radial channel part <NUM> is open towards a radial surface <NUM> of the connecting element <NUM> located at its contact mating part <NUM>. The axial channel part <NUM> and the radial channel part <NUM> of each fluid channel <NUM> are fluidically connected to each other. By this way, there is provided a flow path for coolant liquid, which is described later.

The charging cable mating part <NUM> and the contact mating part <NUM> each are formed essentially as half-cylinders, wherein the contact mating part <NUM> has a wider radial extension than the charging cable mating part <NUM>. Therefore, there is a large contact area between the concerning contact <NUM>, <NUM> and the contact mating part <NUM>, such that a very effective heat transfer from the contact <NUM>, <NUM> to the connecting element <NUM> can be established. The insulating casing <NUM> is slightly larger than the first connecting element <NUM> and the second connecting element <NUM>, such that there is a gap <NUM> between the first and second connecting elements <NUM>, <NUM> and the insulating casing <NUM>, which gap <NUM> provides a fluid channel <NUM> fluidically connecting the radial channel parts <NUM> with the outer fluid channel <NUM> of the charging cable <NUM>.

The entire flow path for the coolant fluid is as follows (see in particular <FIG>, section A and <FIG>): The coolant fluid flows first along the whole length of the charging cable <NUM> through the outer fluid channel <NUM> of the cable <NUM>. At the connection of the charging cable <NUM> to the charging connector <NUM>, the coolant fluid enters into the gap <NUM> and continues to flow along the outer surfaces of the first and second connecting elements <NUM>, <NUM>. At the radial surface <NUM> the fluid enters into the concerning radial channel part <NUM> and flows through the radial channel parts <NUM> and the axial channel parts <NUM> of the fluid channels <NUM>. The fluid exits the axial channel parts <NUM> at the axial surface <NUM> of the charging cable mating part <NUM> and enters into the inner fluid channel <NUM> of the charging cable <NUM>. Therefore, in this example, the outer fluid channel <NUM> provides a supply path for the coolant fluid, while the inner fluid channel <NUM> provides a return path for the coolant fluid.

As the flow path first is through the outer fluid channel <NUM>, the fresh and cool coolant fluid first cools the outer surface of the charging cable <NUM>, such that a very good injury prevention for a user is achieved. The highest thermal duty stems from the conductor cooling, which can be handled very easy due to the large contact area between the connecting elements <NUM><NUM> and the contacts <NUM>, <NUM>, such that heat generated in the contacts <NUM>, <NUM> during charging can effectively be removed by the liquid coolant. The highest heat flux is expected at the base of the connector <NUM>. The highest temperature of the cooling fluid is to be expected at the return to the charging post, which is uncritical, as the hot cooling fluid is contained in the inner fluid channel <NUM> of the charging cable and is therefore effectively shielded from the user.

<FIG> and <FIG> show a partially cut perspective view of an example of the connector <NUM>, in principle. The set of axial/radial channel parts <NUM>, <NUM> in the copper block of the connecting element <NUM>, <NUM> is visualized. The number, position and diameter of the channels <NUM>, <NUM> is a matter of optimization of thermal performance, manufacturing costs, as well as space constraints due to interface of the channels <NUM>, <NUM> to the cable <NUM>.

Claim 1:
A liquid cooled cable arrangement for high-power fast charging of electric vehicles, comprising
a charging connector (<NUM>) and a liquid cooled charging cable (<NUM>), wherein
the liquid cooled charging cable (<NUM>) comprises several insulated positive conductors (<NUM>) and several insulated negative conductors (<NUM>) for supplying charging current and an inner fluid channel (<NUM>) and an outer fluid channel (<NUM>) surrounding the inner fluid channel (<NUM>), the inner fluid channel (<NUM>) and the outer fluid channel (<NUM>) together providing a supply path (<NUM>) and a return path (<NUM>) for liquid coolant, wherein
the positive conductors (<NUM>) and the negative conductors (<NUM>) are arranged within the inner fluid channel (<NUM>), wherein
the charging connector (<NUM>) comprises at least a positive contact (<NUM>) electrically connected to the positive conductors (<NUM>) by a first connecting element (<NUM>) and a negative contact (<NUM>) electrically connected to the negative conductor (<NUM>) by a second connecting element (<NUM>), wherein
the first connecting element (<NUM>) and the second connecting element (<NUM>) each consist of a thermally conductive and electrically conductive material and are electrically isolated from each other, wherein
the first connecting element (<NUM>) and the second connecting element (<NUM>) each are thermally connected to the inner channel (<NUM>) and the outer channel (<NUM>) of the charging cable (<NUM>), such that heat generated in the contacts (<NUM>, <NUM>) during charging can be removed by the liquid coolant,
characterized in that
the first connecting element (<NUM>) and the second connecting element (<NUM>) are designed as metal blocks, which each comprise fluid channels (<NUM>) fluidically connecting the inner fluid channel (<NUM>) and the outer fluid channel (<NUM>) of the charging cable (<NUM>),
wherein the metal blocks of the connecting elements (<NUM>, <NUM>) are made of copper or aluminium, and
the contacts (<NUM>, <NUM>) and the connecting elements (<NUM>, <NUM>) are monolithically formed.