The thin design motor is located
between the 3-cylinder engine and the transmission. The IMA motor
serves a number of functions:
- It assists in vehicle propulsion
when needed, allowing the use of a smaller internal combustion engine.
- It operates as a generator,
allowing excess energy (such as during braking) to be used to recharge
the IMA Battery
Module, and later be used to provide assist.
- It takes the place of the conventional
alternator, providing energy that ultimately feeds the Insight's
conventional 12v electrical system.
- It is used to start the internal
combustion engine very quickly and quietly. This allows the internal
combustion engine to be turned off when not need, without any delay
in restarting on demand.
- It is used to dampen
crankshaft speed variations, leading to smoother idle.
The IMA motor is located between
the internal combustion engine (ICE) and clutch. One end of the IMA
motor rotor is bolted to the ICE crankshaft, and the other end of
the rotor is bolted to the flywheel. Because of the IMA motor adds
rotational mass, the weight of the flywheel can be reduced by an amount
equal to the weight of the IMA motor rotor.
The flywheel retains gear teeth
for the backup 12v starter motor to mesh with when it is engaged.
In manual transmission Insights, as with other manual transmission
vehicles, the clutch also serves as a surface for the clutch.
The IMA motor is
a permanent-magnet type, brushless DC motor.
The only moving part in this type
of motor, the rotor, consists of nothing but permanent magnets. The
electromagnets are located around the perimeter of the stator. There
are several key attributes of this type of motor:
- Because the electromagnets are
located around the perimeter, the electromagnets can be cooled by
conduction to the motor casing, requiring no airflow inside the
motor for cooling. This in turn means that the motor's internals
can be entirely enclosed and protected from dirt or other foreign
- With no windings on the rotor,
they are not subjected to centrifugal forces.
- Commutation (switching current
between different sets of electromagnets to produce rotation) is
not accomplished by any sort of physical switching, such as brushes
that wear out. Instead, this switching is accomplished by an electronic
controller - the Motor
Drive Module. This allows electronic control over torque and
magnet field slip angle, which makes it easy to operate the motor
as a generator.
- Inefficiencies caused by brush
material resistance, and brush drag friction are eliminated.
The IMA motor's disc shaped design
allows it to fit into the same space that would otherwise have been
occupied by a fourth cylinder. The thin, relatively large diameter
shape means that it produces a great deal or torque.