Today we discuss about automatic transmission. We all use bikes and cars. We all know that we need
transmission box or gear box to change the torque according to driving
condition. In earlier we used manual gear box in which there is a hand or foot
operated lever and clutch through witch we shift the gear according driving conditions. But
know the trade is changing and the vehicle moving towards automatic
transmission.
Now days many cars and scooters used automatic transmission
which are easy to handle and user friendly. But a question is arising that how
the automatic transmission works? Are we using the conventional gearbox in
automatic transmission or there is other arrangement? Will we change our manual
transmission vehicle into automatic transmission without changing the gearbox?
Today I will discuss on that topic and if any question arise
in your mind kindly put in comment box. I will revert back you soon. Before
starting this post fist you read the following post.
Principle of Automatic Transmission:
In the manual transmission
we used sliding mesh or synchromesh gearbox but in automatic transmission we
used epicyclical gear box. This type of gear box uses no sliding dogs or gears to engage
but different gear speeds are obtained by merely tightening brake bands on gear
drum. It consists of a sun gear, pinion or planet gear and the ring gear.
The ring gear contains teeth on it inner circumference and it surrounded
by a brake band. The brake band is operated by the hydraulic pressure exerted
by the hydraulic oil. This is control by the electronic sensor or the movement
to vehicle speed, load and the accelerator valve opening. The planet gears are
in constant mesh with both thee sun gear and ring gear and are free to rotate
on their axes carried by the carrier frame which in turn is connected to the
driver shaft.
When the ring gear is locked by the brake band, the rotating sun
gear causes the planet gears to rotate. Since the ring gear cannot move. The
planet gears are forced to climb over it. During this position, the ring gear
acts as track for the planet gears to move over. The driven shaft which is
connected to the planet gear carrier is thus rotate. When the ring gear is
released, it is free to move in consequence to the rotation of planet gears
which rotate around their axis. During this position, there is no movement of
planet carries and hence the driven shaft remains stationary. A planetary gear
box contains a numbers of such units to obtain various speed reductions.
Component of Automatic Transmission:
The main component of the automatic transmission is the
converter housing case, oil pan and the extension housing. The converter housing encloses the torque
converter and the case contains epicyclical gear train while the extension
housing encloses the output shaft. The oil pan is bolted to the case. The
entire transmission unit is attached to the engine block by means of bolts
through holes in the converter housing flange.
Working of Automatic Transmission:
The automatic transmission is same work as the manual
transmission except it is control by the brake arrangement operated hydraulically.
In the automatic transmission the engine shaft is connected to the clutch and
the further connected to the turbine of the torque converter. The torque
converter drives the ring gear of first gear train through a free wheel. The drive
of the ring gear of the second gear train is then taken form the planet carrier
of the first gear train so that the two act in series. This arrangement gives three forward and one
reverse speed by subsequently application of brake.
The selection of the particular gear and application of
corresponding clutch and brake is done hydraulically. The hydraulic pressure I regulated
by the car speed that control oil pressure on one side of the shift valve and
the throttle opening controlled by the driver through the accelerator pedal
which controls oil pressure on other side of the shift valve.
Today we have discussed about Automatic Transmission : Principle and Working. If you got any query kindly ask by commenting.
Today we have discussed about Automatic Transmission : Principle and Working. If you got any query kindly ask by commenting.