Environmental Engineering Reference
In-Depth Information
Table 1.12 Hybrid propulsion system component inertias
Value (kg m
2
)
Component
Automotive Lundell alternator, 14 V, 120 A, belt driven, air cooled
0.001
42 V PowerNet Integrated Starter-Alternator, 10 kW, 180 Nm,
280 mm OD for transmission integration
0.082
Automatic transmission torque converter, impeller (attached to engine
crankshaft)
0.12
Automatic transmission torque converter, turbine (attached to
transmission input shaft)
0.04
Transmission gearbox
0.0001
Engine crankshaft
0.00015
Engine crankshaft mounted flywheel plus ring gear (gasoline engines)
0.14
Engine crankshaft mounted flywheel plus ring gear (CIDE-diesel
engines)
0.18
Wheel (each)
0.31
rotor diameter of 235 mm and the approximation for average mass density noted
above. In this case the polar moment of inertia becomes
J
0
= 0.082 kg m
2
.
The remaining inertia to be evaluated in the mass factor expression is wheel
inertia. In order to estimate wheel inertia, some knowledge of the wheel mass is
required. Wheel mass includes tyre, rim and hub, and disc- or drum-rotating portion
of brake assembly. If these data are available it should be used. Otherwise the
following procedure yields some useful approximations. Start with a breakdown of
the vehicle's major assemblies.
In Table 1.13 the ratio of sprung to unsprung mass turns out to be 3.56:1
empty. At the design mass, gross vehicle mass, this ratio becomes 6.74:1. Now, for
a further approximation of the total unsprung mass, about 60% of this is linkages,
strut components, brake calipers etc. This leaves 94.4 kg for four wheels, or 23.6 kg
each. Using the same mass density approximation as the Lundell alternator and the
stated rolling radius (0.284 m), the wheel inertia is 0.952 kg m
2
. The equivalent
mass due to wheels in this case is 47.2 kg (relatively close to the generic value
Table 1.13 Vehicle mass breakdown (Focus 5 door)
Component
Value (kg)
(%) Total
Body in white (BIW)
437
40.5
Powertrain (engine + transmission + propeller shaft + axles)
197
18.3
Interior trim (seats, console, all upholstery, lighting)
137
12.7
All electrical (harnesses, modules, switches) and fuel
system
35
3.25
Fuel system (tank, lines, filters and ½ tank gasoline)
13.5 gallons tank
35
3.25
Total of all sprung components
841
78
Vehicle curb mass (Table 1.10)
1,077
100
Unsprung mass (curb - sprung mass),
m
us
236
21.9
