Automotive Engineering - April 2022 - 24

Engineering a
'MAVERICK' HYBRID
TRANSMISSION
ELECTRIFICATION FEATURE
Hybrid-powertrain
engineer Manny
Barbarena's team
focused on the revised
HF45's vehicle-level
functionality.
HF45's Ford-Aisin-TRW heritage
The HF45 has an interesting heritage, according to Craig Renneker,
VP product engineering at American Axle & Manufacturing. Its predecessor
HF35 was one of 18 transmissions launched by Ford between
2000 and 2018, when Renneker was a chief engineer in the
company's Transmission & Driveline Engineering.
" The HF35 was one of the great successes, " he said proudly. It was
based on the Aisin AW PowerSplit architecture (itself inspired by early1970s
TRW technology) enabled by an agreement between Ford and
Toyota. The deal allowed Ford to use the powerflow of the first-generation
Aisin AW models HD-10 and HD-20 for their own product.
According to Renneker, the powerflow of the Aisin and Ford HF35 " are
nearly identical, as are the motors and Denso inverter architecture. "
Ford Escape taxi cabs operating in New York City proved the
basic design's durability. Renneker recalled getting a hybrid Escape
cab back from the field with 450,000 miles (724,205 km) on it that
" was still running fine with the original battery. " A full teardown
revealed transmission internal parts that looked perfect, " good for
many more miles, " he said.
Renneker points out that contrary to some media articles, the
The collaboration
between Design
and Manufacturing
engineering
to support the
Maverick HF45
was an engineer's
ideal, said Abdul
Hajiabdi.
HF35/HF45 design is " not a typical CVT in which the torque multiplication
ratio between the engine and the wheels can be varied continuously. "
He noted that with the Toyota/Aisin PowerSplit concept,
the ratios themselves are fixed, but in Ford's unit, one of the electric
motors is used to control engine speed to optimize best-fuel-economy
or best-power conditions. All of this is managed by the software,
with no driver input required. " This speed control is continuously
variable, so the 'CVT' terminology is still okay, " he said.
Lindsay Brooke
Close collaboration between the Design and Manufacturing
engineering groups made it happen.
" Until the in-house motor and Maverick program came along,
the relationship between the Design team that I represent and
the Manufacturing team at Van Dyke [Ford's Electric Powertrain
Center factory] was typically a three-way conversation that
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included suppliers, " Hajiabdi noted. " That changed with the
introduction of the in-house program, because now the full
design ownership is with Ford. The full manufacturing ownership
is still with Ford. So now we have a full in-house team that
works with what we call PTME, the manufacturing-engineering
team, producing the parts together.
" We were able to come up with the design, take it to the
shop, prototype build it, check it for process and quality
prove-out, " he continued. " In doing so, we noticed that there
are certain design criteria that looked good on paper but
were not manufacturable. " The result was " what the true
engineer looks for, " he said: the 'sweet spot' between the
high function sought by the designers, and manufacturability
at scale, with high quality and low cost. " It's the start of
in-house electric machines to come, including F-150
Lightning, " he asserted.
The Maverick hybrid's 2,000-lb (907-kg) trailer-tow capability
put transmission thermal management into focus. Initially
this presented a challenge, the engineers recalled, because taking
an all-new electric machine with its own heat-rejection signature
and cooling it in the carryover HF45 " was not a straight
plug-and-play, " Barbarena noted. Clever internal " tuning " and
attention to lubricant flow ensured the hybrid pickup withstands
SAE J2807 tow testing and has helped the powertrain
team close the tow-capacity gap with Maverick turbo gas-engine
models, which is 4,000 lb. (1814 kg).
AUTOMOTIVE ENGINEERING
FROM TOP: FORD; LINDSAY BROOKE
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Automotive Engineering - April 2022

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