Environmental Engineering Reference
In-Depth Information
Solution:
Using the same expression developed in Example 4 results in
r
W
w
MG1
max
g
fd
g
Low
¼
ð
0
:
327
Þð
1507
:
7
Þ
ð
3
:
769
Þð
3
:
9
Þ
V
Low
¼
¼
33
:
54 m
=
s
¼
75mph
r
W
w
MG1
max
g
fd
k
E2
¼
ð
0
:
327
Þð
1507
:
7
Þ
V
WOT
¼
¼
68
:
8m
=
s
¼
154mph
ð
3
:
769
Þð
1
:
9
Þ
Clearly, the introduction of gear shifting into the single mode eCVT has
enhanced its capability for high speed operation. This, coupled with a higher output
V6 engine and more powerful battery, yields a vehicle net propulsion power of
254 kW sufficient to sustain the high speeds. However, in the production of GS450h
Toyota has introduced a rev-limiter that restricts top end speed to 131 mph.
2.3.3 Continuously variable transmission derived
The driveability concern of torque holes in a step ratio transmission or the corre-
sponding losses in an automatic transmission are partially offset in a CVT. The
CVT adjusts its ratio continuously over its gear shift ratio coverage range,
G
src
.In
the CVT,
G
src
is maximally 6:1.
In Figure 2.26, the belt type CVT has the engine input applied to its primary
side through a mechanical clutch and an M/G connected permanently at the pri-
mary, but outboard of the engine. The secondary side of the CVT is connected via
gears to the transmission final drive as shown. The CVT itself can be either a belt
(Reeves) or a toroidal (Torotrak) system.
CVT
Engine
Motor
Accessory
drive
Figure 2.26 CVT hybrid (from Reference 16)
The Reeves type CVT with a rubber belt is commonly found in snowmobile
transmissions. The steel belt (Van Doorne) CVT having offset axes is ideal for
mounting in small front wheel drive vehicles. The Van Doorne is a steel compression
