| Arvin Meritor Light Vehicle Systems
has developed a next-generation door latch.
The low-energy release LER Hybrid latch’s electrical actuation provides
low operating forces, quiet operation, improved passive entry function
and ease of customisation.
Design and development was carried out at the firm’s Birmingham,
UK, facility. Production is expected to start in 2010–12 and the
latch will be aimed initially at the C and D segments.
A product range will cover latches for sliding doors, tailgates and boots.
Chief engineer for latches and actuators Gurbinder Singh Kalsi said: “We
want to take passive entry into a wider range of product segments. We
can see the LER Hybrid replacing current remote central locking systems.”
OEMs are increasing door seal compression forces to reduce cabin noise.
These forces, working at the latch claw, must be overcome when the interior
handle is pulled. These are typically 300–400N but rise to 600N
in premium vehicles fitted with power-close doors.
In a crash, seal loads can exceed 4,000N, making it impossible to open
the door from the inside with a conventional latch. The LER, tested with
this load, required an effort of only 32N on the handle.
“The safety benefits are obvious,” said Singh Kalsi. Two European
OEMs are already evaluating prototypes.
The latch has an additional pawl to boost the lever ratio by a factor
of 20, enabling release forces as low as 10N. As a result, door handles
can be made much smaller, improving packaging, positioning and aesthetics.
All locking logic is software-controlled, so extra functions can be added
without changing the lock architecture. Current designs require extra
motors for features such as deadlocking and electrical child safety locking
with obvious size and cost disadvantages.
Full mechanical redundancy ensures fail-safe operation, addressing a weakness
of the previous E-latch, which only worked electrically.
The LER Hybrid is smaller, lighter and contains up to 60 per cent fewer
parts than current designs with equivalent functions.
Arvin Meritor says if parts of the locking system such as actuating cables
are down-gauged in line with the reduced actuation forces, total system
cost reductions of up to 50 per cent are possible.
Passive entry systems can be caught out because it’s possible to
fully actuate the outside door handle before the electronics can register
the input. A second operation of the outside handle is then required.
Singh Kalsi said: “The LER, which employs power release, will release
as the handle is operated, avoiding a double pull.”
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