Automobile self
starter
An automobile self-starter
(commonly "starter motor" or simply "starter") is an electric motor that
initiates rotational motion in a car's internal combustion engine before
it can power itself.
Electric starter
The modern starter motors are
called truck parts
which is made of either a permanent-magnet or a series- or
series-parallel wound direct current electric motor with a solenoid
switch (similar to a relay) mounted on it. When current from the
starting battery is applied to the solenoid, usually through a
key-operated switch, it pushes out the drive pinion on the starter
driveshaft and meshes the pinion with the ring gear on the flywheel of
the engine.
The solenoid also closes
high-current contacts for the starter motor, which begins to turn. Once
the engine starts, the key-operated switch is opened, a spring in the
solenoid assembly pulls the pinion gear away from the ring gear, and the
starter motor stops. In this manner, drive is transmitted through the
pinion to the flywheel ring gear, but if the pinion remains engaged (as
for example because the operator fails to release the key as soon as the
engine starts), the pinion is spin independently of its driveshaft.
This
prevents the engine driving the starter, for such back drive would cause
the starter to spin so fast as to fly apart. However, this sprig clutch
arrangement would preclude the use of the starter as a generator if
employed in hybrid scheme mentioned above; unless modifications are
made.
The Bendix system places the
starter drive pinion on a helically-cut driveshaft. When the starter
motor begins turning, the inertia of the drive pinion assembly causes it
to ride forward on the helix and thus engage with the ring gear. When
the engine starts, back drive from the ring gear causes the drive pinion
to exceed the rotative speed of the starter, at which point the drive
pinion is forced back down the helical shaft and thus out of mesh with
the ring gear.
The Folo-Thru drive contains a
latching mechanism and a set of flyweights in the body of the drive
unit. When the starter motor begins turning and the drive unit is forced
forward on the helical shaft by inertia, it is latched into the engaged
position. Only once the drive unit is spun at a speed higher than that
attained by the starter motor itself (i.e., it is backdriven by the
running engine) will the flyweights pull radially outward, releasing the
latch and permitting the overdriven drive unit to be spun out of
engagement. In this manner, unwanted starter disengagement is avoided
before a successful engine start.
Gear-reduction starters
Chrysler Corporation contributed
materially to the modern development of the starter motor. In 1962,
Chrysler introduced a starter incorporating a gear train between the
motor and the driveshaft. Rolls Royce had introduced a conceptually
similar starter in 1946, but Chrysler's was the first volume-production
unit. The motor shaft has integrally-cut gear teeth forming a drive gear
which mesh with a larger adjacent driven gear to provide a gear
reduction ratio of 3.75:1. This permits the use of a higher-speed,
lower-current, lighter and more compact motor assembly while increasing
cranking torque.
This starter formed the design
basis for the offset gear reduction starters now employed by about half
the vehicles on the road, and the conceptual basis for virtually all of
them. Many Japanese automakers phased in gear reduction starters in the
1970's and 1980's. Light aircraft engines also made extensive use of
this kind of starter, because its light weight offered an advantage.
Those starters’ not employing offset gear trains like the Chrysler unit
generally employ planetary epicyclical gear trains instead.
Direct-drive
starters are almost entirely obsolete owing to their larger size,
heavier weight and higher current requirements. Ford also issued a
nonstandard starter, a direct-drive "movable pole shoe" design that
provided cost reduction rather than electrical or mechanical benefits.
This type of starter eliminated the solenoid, replacing it with a
movable pole shoe and a separate starter relay. The Ford starter
operated as follows:
1. The operator closed the
key-operated starting switch.
2. A small electric current
flowed through the starter relay coil, closing the contacts and sending
a large current to the starter motor assembly.
3. One of the pole shoes, hinged
at the front, linked to the starter drive, and spring-loaded away from
its normal operating position, swung into position. These moved a pinion
gears to engage the flywheels ring gears, and simultaneously closed a
pair of heavy-duty contacts supplying current to the starter motor
winding.
4. Starter motor cranked the
engine until it started. An overrunning clutch in the pinion gear
uncoupled the gear from the ring gear.
5. A spring retracted the pole
shoe, and with it, the pinion gear.
6. The operator released the
key-operated starting switch, cutting power to the starter motor
assembly.
Pneumatic starter
Many gas turbine engines and Diesel
engines, particularly on truck partss, use a pneumatic self-starter. The
system consists of a geared turbine, an air compressor and a pressure
tank. Compressed air released from the tank is used to spin the turbine,
and through a set of reduction gears, engages the ring gear on the
flywheel, much like an electric starter. The engine, once running,
powers the compressor to recharge the tank.
Since large truck partss typically
use air brakes (auto part), the system does double duty, supplying
compressed air to the brake system. Pneumatic starters have the
advantages of delivering high torque, mechanical simplicity and
reliability. They eliminate the need for oversized, heavy storage
batteries in prime mover electrical systems.
Second method, for large diesel
engines like truck parts automobiles, uses additional valves in cylinder
heads. Compressed air is let in the cylinders so that its pressure
pushes pistons down when appropriate; at the upward piston movement, air
is discharged through normal exhaust valves.
Auxiliary starter engine
Auxiliary start used where large,
high power Diesel engine, such as those used in off-road heavy
equipment, may have a small gasoline-powered are used.
These were also sometimes called
pony engines. On some applications, they shared the same cooling system
and oil supply. As the pony engine warmed up, it circulated warm coolant
and warm oil in the diesel engine. In addition to making it easier to
crank, it improved the service life.
Static-start engine
Another way to provide for shutting
off a car's engine when it is stopped, then immediately restarting it
when it's time to go, is by employing a static-start engine. Such an
engine requires no starter motor, but employs sensors to determine the
exact position of each piston, then precisely timing the injection and
ignition of fuel to turn over the engine.
Other considerations include
maintenance services on the engine, such as changing spark plugs and
malfunctions in the pistons positioning system, these will release all
the fuel mixture inside the cylinders and render the engine non-startable,
unless there is the starter to provide the necessary assistance.
For
Diesel engines, this concept will requires even higher precisions than
the extremely high tolerances the Spark Ignition Engines already
require; due to their extremely high compression ratios. These
ultra-tight tolerances will be detrimental to the free movement of the
pistons - if not impossible - once the engine reaches operating
temperature, due to metal expansion. Thus, with the current automotive
technologies and engine designs, we will probably not see the starter
disappear anytime soon.
