to the Zeroshift Electric Vehicle Transmissions brochure

Zeroshift transmission for
electric vehicles
The World’s Most Efficient Automatic Transmission
Milton Keynes Headquarters (UK)
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Batteries are the Achilles heel of
electric vehicles
• High cost (ca $10,000 for
Leaf)
• Low range – theoretical
max 100 miles
– Range anxiety
• Recharge
– 8 hours standard power
– 45 kw for rapid charge
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Efficiency of electric cars
• Efficiency of motor falls off at low and high speeds.
• Poor on stop-start urban cycle and cruise / range.
• Require over-size motor to compensate for lack of ratios.
Sweet
spot
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Motor speed
Benefits of Transmissions in
electric vehicles
• Gear ratios can keep the motor of an electric
vehicle in its ‘sweet spot’ of highest power and
efficiency.
• 10 % improved efficiency….
– Smaller / cheaper battery
– Smaller / lighter motor
• Better performance
–
–
–
–
–
Better launch
Greater range
Better ability on gradients
Faster acceleration
Faster cruise speed in overdrive
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Problems with transmission for
electric vehicles
• Conventional automatics introduce 10 %
losses and extra weight, plus cost,
negating benefit.
• Manual gearboxes are efficient but
interrupt torque during gear changes.
Need a clutch.
• Zeroshift provides seamless automatic
transmission with minimal efficiency losses
and no clutch.
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7
No Clutch
The E Machine does not require a clutch for launch.
Zeroshift does not require a clutch to shift.
The dampers in the hub cater for E machine inertia.
E machine assists to modify it’s speed.
The result is low cost low losses.
The losses when in gear are nil.
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DAMPER ANALYSIS
55
Solid
50
45
40
35
Force (kN)
Elastomer
30
25
20
15
10
ATF
5
0
0.23
0.24
0.25
0.26
0.27
0.28
0.29
0.3
0.31
0.32
Tim e(s)
• Linear impact testing replicating the impact force of a max rpm 1-2 shift
showed fluid damping at source to be a viable shock mitigating solution.
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DAMPER ANALYSIS
Undamped
Damped
• The damped system was applied to a complete driveline model developed using
Matlab/Simulink software.
• The dynamic response of all sub-elements were all independently correlated to the
development vehicle.
• The sub-elements were assembled in a model-in-the-loop scenario whereby the same
controller on the vehicle was used to control the model.
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DAMPER DESIGN
• Annular clearance output shaft mounted dampers.
• Dampers are passive, though tuneable for different
applications.
• Damper functionality includes return to centre and a
patented secondary interlock system.
• Re-circulated transmission fluid is pumped into
damped gears through the shaft.
• Sealed dampers use silicone fluid and are sealed
for life.
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DAMPER OPTIMISATION
Input shaft damper at 300 Nm
07-May-2009 16:37:00
Input shaft damper at 300 Nm
DUAL PISTON HANDOVER PRESSURE v PCR, Piston area
07-May-2009 16:37:00
SINGLE PISTON SLOWDOWN SPEED v clearance
200 bar
150
100 bar
200
70 bar
250
300
50 bar
350
400
35 bar
450
• The models can analyse damper performance
for different transmission architectures.
500
50
10
Piston xarea*PCR mmcu x 1000
• Damper sizing and optimisation is achieved
using a set of complex simulation models.
SINGLE PISTON x-sec area sq mm
100
90 rpm
70 rpm
15
50 rpm
20
30 rpm
25
30
20 rpm
55
60
65
70
75
80
PCR mm
85
90
95
100
0
0.5
1
1.5
flowarea sqmm
2
2.5
• Peak pressures and steady state end of travel
speeds are tuneable through piston vs. flow
area adjustment.
• Bulk modulus, dynamic viscosity vs.
temperature and density of the damping
medium are considered.
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3
Test Drive…
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