The
possibilities gained by these thermoplastic compounds are demonstrated in a new
design concept from Lanxess for charging inlets. These are installed in battery
electric vehicles and accommodate the charging coupler of the external charging
station.
“Our
approach is aimed at using a modular configuration to get the right material in
the right place to meet the complex requirements applicable to the various
components with the utmost precision,” explains Gregor Jaschkewitz, application
developer at the High Performance Materials (HPM) business unit, who devised
the design, adding that “At the same time, a high level of functional integration
is intended to make it as easy as possible to assemble the entire unit, which
means screwless assembly and minimal components in order to keep costs low.”
Transfer of
expertise from projects
The
design is the product of collaborative discussions with manufacturers of
charging systems and incorporates the experience that Lanxess has already
accumulated in numerous charging infrastructure development projects. “This
means that it also satisfies a desire expressed by many manufacturers to have
the ability to be as flexible as possible when it comes to charging inlet
sealing,” says Jaschkewitz. O-rings, sealing cords or family seals can be used,
for example, as can be employed lip seals manufactured in a two-component
injection molding process.
Integrated thermal
management
The
key elements of this charging inlet design are the front and rear housings, a
socket for the connector from the charging station and an actuator. The latter
locks the connector in place to prevent it from being accidentally or
deliberately pulled out during the charging process.
The pin holder is another
essential element. It holds the metallic connector pins in place, as well as a
printed circuit board (PCB) with cables for charging with direct or alternating
current, among others. Particular attention was paid to the design of the pin
holder.
It positions the cables such that the heat produced during charging is
dissipated not only through them but also via the other cables not in use.
“This means that the pin holder supports the thermal management and thus makes
fast charging at high currents easier,” says Jaschkewitz.
Once
the cables and contact pins have been placed in the holder and the PCB has been
clipped in, all the charging inlet components are put together with the aid of
snap fits. The cables are fastened in place under minimum strain so that they
cannot become detached in the housing. Jaschkewitz adds, “The ability to join
the components without the need for screws simplifies the assembly process and
associated logistics, which, in turn, cuts manufacturing costs.”
High material
requirements fulfilled
Plastics
for charging inlets are required to comply with the IEC 62196-1 standard and
deliver high electrical insulation resistance as well as high dielectric
strength and tracking resistance. Good fire-retardant properties are also
essential. Parts that come into direct contact with live components must pass a
glow-wire end product test (GWEPT) in accordance with IEC 60695-2-11 at a
glow-wire ignition temperature of 850 °C.
After being stored at 80 °C for seven
days, the plastic parts must not exhibit any surface changes – such as cracks –
caused by aging. High-grade mechanical properties (e.g. good toughness) are
also required to ensure that the charging inlet is not susceptible to bumps or
vandalism. “Our material solutions include compounds that are ideally suited to
this range of requirements. In some cases, versions developed specifically for
electric vehicles are also available,” says Sarah Luers, application developer
at HPM.
“This
includes, for example, highly weather- and UV-resistant products for housings
as well as materials exhibiting low shrinkage and warpage for components that
need to be particularly dimensionally stable. Thermally conductive polyamide 6
compounds with good mechanical properties are intended for use in the pin
holder, which is subject to heavy thermal loads. This also includes product
types that pass the UL 94 flammability test prescribed by the US Underwriters
Laboratories Inc. testing institute with a V-0 rating,” she adds.
Lanxess
assists charging system manufacturers with an extensive range of services
through its HiAnt service brand. On behalf of its project partners, for
example, it calculates and simulates how component geometry and material will
affect the generation of heat in the component. Other services include
performing important flammability testing in compliance with standards and
conducting mechanical testing such as ball drop tests.
Lanxess
is currently considering applying the new design to further assemblies of the
charging infrastructure – such as the charging plug. The design and materials
expertise built up during work on the vehicle charging inlets can be deployed
to a large extent here because the requirements are very similar.