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AUTOMATIC TRANSMISSION
AUTOMATIC TRANSMISSION
• Automatic transmission and transaxles have similar
   components. Three basic parts include:
1. Torque Converter.
2. Gear train: planetary gear sets
3. Hydraulic system
• Torque converter connects to the crankshaft and transmits
   engine power to the gear train.
• Hydraulic pressure acting through the automatic-transmission
   fluid (ATF) in the transmission or transaxle produces the
   shifts.
Automatic Transmission
Gear-Shift Mode
A/ T OPERATION
• Most A/T have 3 or four forward speed.
• They also have PARK, NEUTRAL, and REVERSE.
• 4th speed is usually has overdrive ratio. Some
  others have fifth gear which is an overdrive.
• A typical A/T move the vehicle in 1st gear. Then
  it shifts to 2nd, 3rd & 4th without assistance from
  driver . They happen automatically as vehicle
  speed increases & the engine load or throttle
  opening decreases.
• To slow and stop the vehicle the driver only
  needs to release accelerator pedal or apply
  brake.
• The A/T disengages the torque converter
  clutch & automatically downshifts until 1st gear
  when the vehicle stops.
• Slippage in the torque converter allows the
  engine to idle with the transmission in gear.
TORQUE CONVERTER
•  Torque converter is a form of fluid coupling.
•  It uses a fluid ( such as ATF) and vaned rotors to transmit power between shafts.
   The torque converter is filled with ATF.
• When the engine runs, power flows from the crankshaft trough the fluid to the
   transmission input shaft.
• Torque converter can be divided into 3 main members:
a. Impeller: The impeller, also known as the pump, is the driving member and
   rotates with the engine.
b. Turbine: The impeller vanes pick up fluid in the converter housing and direct it
   toward the turbine. Unless the torque converter is locked, the turbine is normally
   turns slower than the impeller.
c. Stator: Fluid flow drives the turbine, and when the flow between the impeller and
   turbine is adequate, the turbine rotates and turns the transmission input shaft. A
   torque converter contains the stator, or reactor, a reaction member mounted on a
   one-way clutch.
• The vanes used in each of the three elements of a torque converter are curved to
   increase the diversion angle of the fluid. This also increases the force exerted by
   the fluid and improves the hydraulic advantage.
Automatic Transmission
Automatic Transmission
• The Pump
  Automatic transmissions have a neat pump, called a gear
  pump. The pump is usually located in the cover of the
  transmission. It draws fluid from a sump in the bottom of the
  transmission and feeds it to the hydraulic system. It also feeds
  the transmission cooler and the torque converter.
• The inner gear of the pump hooks up to the housing of the
  torque converter, so it spins at the same speed as the engine.
  The outer gear is turned by the inner gear, and as the gears
  rotate, fluid is drawn up from the sump on one side of the
  crescent and forced out into the hydraulic system on the
  other side.
Automatic Transmission
•   When the engine runs, the fluid
    between the vanes in the impeller
    is thrown outward by the
    centrifugal force.
•   The fluid strikes the turbine vanes.
    This action produce rotating force
    on the turbine and the transmission
    input shaft attached to it.
•   The vanes then directs the fluid
    toward the centre of the turbine
    and back toward the centre of the
    impeller.
• STATOR:
• To make the torque converter more efficient, a 3 rd member or
  stationary reactor called stator is placed between the impeller
  & turbine.
• The stator have curve vanes that change the direction of the
  fluid after it leaves the turbine. This causes the fluid to pass
  trough the impeller & then push on the turbine vanes again
  with a helping force that aid rotation. The result is torque
  multiplication under certain condition.
• Torque multiplication: in many torque converter the torque is
  more than double.e.g, 1.35N.m of torque entering the
  impeller, the turbine delivers more than 2.7N.m of torque to
  the transmission input shaft. Torque multiplication occurs only
  when the impeller turns faster than the turbine.
Fluid flow within a torque converter. The stator redirects
   the fluid that is thrown out by the turbine, thereby
                    improving efficiency.
Automatic Transmission
Fluid pumped into the turbine by the impeller not
only creates rotary fluid flow but also vortex flow that
   increases the efficiency of the torque converter.
STATOR ONE- WAY CLUTCH
• As the vehicle approaches cruising speed, the turbine
  begins to catch up with the impeller (coupling point).
• The fluid leaving the turbine is moving at about the
  same speed as the impeller. This fluid could pass
  directly into the impeller without stator action. In
  fact, the stator vane are now in the way. The fluid is
  striking the back sides of the stator vanes.
• To allow the stator vanes to move out of the way,
  the stator mounts on a one- way clutch (overrunning
  clutch)
One- way Clutch
• A mechanical device that tranmits torque in one direction &
  permits free rotation in the opposite side.
• When the speed difference between the impeller & the
  turbine is large, the fluid from the turbine tries to spin the
  stator backward. This causes the one- way clutch to lock the
  stator to its shaft. When the speed difference is small, the
  clutch unlocks & allows the stator to freewheel. 2 types of
  one way clutch are roller clutch & sprag type clutch.
Automatic Transmission
Automatic Transmission
TORQUE CONVERTER CLUTCH
            (TCC)
• Function:
A lockup torque converter eliminates the 10%
  slip that takes place between the impeller and
  turbine at the coupling stage. The
  engagement of a clutch between the impeller
  and the turbine assembly greatly improves
  fuel economy and reduces operational heat
  and engine speed.
Automatic Transmission
Automatic Transmission
• The lock- up torque converter (TCC) has a
  lock- up or clutch piston with a lining of
  friction material.
• The piston or plate attaches to the turbine
  hub.
• Isolator springs helps dampen the shock of
  engagement as the torque converter locks.
  They also dampen out the power pulse from
  the engine while the torque converter is
  locked.
TCC operation
• The clutch is controlled by hydraulic valves, which are
  controlled by the PCM. The PCM monitors operating conditions
  and controls lockup according to those conditions.
• When the converter is not locked (clutch disengage), fluid
  enters the converter and moves to the front side of the piston,
  keeping it away from the shell or cover. Fluid flow continues
  around the piston to the rear side and exits between the neck
  of the torque converter and the stator support.
• During the lockup mode ( clutch engage), the switch valve
  moves and reverses the fluid path. This causes the fluid to
  move to the rear of the piston, pushing it forward to apply the
  clutch to the shell and allowing for lockup. Fluid from the front
  side of the piston exits through the turbine shaft that is now
  vented at the switch valve.
• Reduction in engine speed
  and the elimination of the
  normal slippage in the
  torque converter improves
  fuel economy.
• The torque converter clutch
  is released during rapid
  acceleration for maximum
  torque multiplication
  through the torque
  converter for best
  acceleration.
HYDRAULIC CIRCUIT (HOMEWORK)
• Revise a basic hydraulic circuit components:-
a.   Hydraulic pump
b.   Control valves (directional control)
-    Pressure relief valves
-    Pressure regulators
-    Shuttle valves
-    Check valves
c. Actuators( Hydraulic cylinder, Swashplates, Hydraulic motor , hydrostatic
     transmission, Brakes)
d. Reservoir
e. Accumulators
f. Hydraulic fluid
g. Filters
h. Tubes, pipes and hoses
i. Seals, fittings and connections
A/T GEAR- TRAIN
A/T GEAR- TRAIN
• Gear-train consist of the following:-
a. Planetary gearset: A compound epicyclic planetary gearset,
   whose bands and clutches are actuated by hydraulic servos
   controlled by the valve body, providing two or more gear
   ratios.
b. Clutches and bands: to effect gear changes, one of two types
   of clutches or bands are used to hold a particular member of
   the planetary gearset motionless, while allowing another
   member to rotate, thereby transmitting torque and producing
   gear reductions or overdrive ratios. These clutches
   (overrunning clutch) are actuated by the valve body (see
   below), their sequence controlled by the transmission's
   internal programming.
C. Valve body: hydraulic control center that receives pressurized fluid from
the main pump operated by the fluid coupling/torque converter. The
pressure coming from this pump is regulated and used to run a network of
spring-loaded valves, check balls and servo pistons. The valves use the pump
pressure and the pressure from a centrifugal governor on the output side (as
well as hydraulic signals from the range selector valves and the throttle valve
or modulator) to control which ratio is selected on the gearset; as the vehicle
and engine change speed, the difference between the pressures changes,
causing different sets of valves to open and close. The hydraulic pressure
controlled by these valves drives the various clutch and brake band actuators,
thereby controlling the operation of the planetary gearset to select the
optimum gear ratio for the current operating conditions. However, in many
modern automatic transmissions, the valves are controlled by electro-
mechanical servos which are controlled by the electronic engine control unit
(ECU) or a separate transmission control unit (TCU, also known as
transmission control module (TCM).
a. PLANETARY GEARS
• Any planetary gearset has three main components:
a. The sun gear
b. The planet gears and the planet gears' carrier
c. The ring gear
• Each of these three components can be the input,
   the output or can be held stationary. Choosing which
   piece plays which role determines the gear ratio for
   the gearset.
Automatic Transmission

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Automatic Transmission

  • 2. AUTOMATIC TRANSMISSION • Automatic transmission and transaxles have similar components. Three basic parts include: 1. Torque Converter. 2. Gear train: planetary gear sets 3. Hydraulic system • Torque converter connects to the crankshaft and transmits engine power to the gear train. • Hydraulic pressure acting through the automatic-transmission fluid (ATF) in the transmission or transaxle produces the shifts.
  • 5. A/ T OPERATION • Most A/T have 3 or four forward speed. • They also have PARK, NEUTRAL, and REVERSE. • 4th speed is usually has overdrive ratio. Some others have fifth gear which is an overdrive. • A typical A/T move the vehicle in 1st gear. Then it shifts to 2nd, 3rd & 4th without assistance from driver . They happen automatically as vehicle speed increases & the engine load or throttle opening decreases.
  • 6. • To slow and stop the vehicle the driver only needs to release accelerator pedal or apply brake. • The A/T disengages the torque converter clutch & automatically downshifts until 1st gear when the vehicle stops. • Slippage in the torque converter allows the engine to idle with the transmission in gear.
  • 7. TORQUE CONVERTER • Torque converter is a form of fluid coupling. • It uses a fluid ( such as ATF) and vaned rotors to transmit power between shafts. The torque converter is filled with ATF. • When the engine runs, power flows from the crankshaft trough the fluid to the transmission input shaft. • Torque converter can be divided into 3 main members: a. Impeller: The impeller, also known as the pump, is the driving member and rotates with the engine. b. Turbine: The impeller vanes pick up fluid in the converter housing and direct it toward the turbine. Unless the torque converter is locked, the turbine is normally turns slower than the impeller. c. Stator: Fluid flow drives the turbine, and when the flow between the impeller and turbine is adequate, the turbine rotates and turns the transmission input shaft. A torque converter contains the stator, or reactor, a reaction member mounted on a one-way clutch. • The vanes used in each of the three elements of a torque converter are curved to increase the diversion angle of the fluid. This also increases the force exerted by the fluid and improves the hydraulic advantage.
  • 10. • The Pump Automatic transmissions have a neat pump, called a gear pump. The pump is usually located in the cover of the transmission. It draws fluid from a sump in the bottom of the transmission and feeds it to the hydraulic system. It also feeds the transmission cooler and the torque converter. • The inner gear of the pump hooks up to the housing of the torque converter, so it spins at the same speed as the engine. The outer gear is turned by the inner gear, and as the gears rotate, fluid is drawn up from the sump on one side of the crescent and forced out into the hydraulic system on the other side.
  • 12. When the engine runs, the fluid between the vanes in the impeller is thrown outward by the centrifugal force. • The fluid strikes the turbine vanes. This action produce rotating force on the turbine and the transmission input shaft attached to it. • The vanes then directs the fluid toward the centre of the turbine and back toward the centre of the impeller.
  • 13. • STATOR: • To make the torque converter more efficient, a 3 rd member or stationary reactor called stator is placed between the impeller & turbine. • The stator have curve vanes that change the direction of the fluid after it leaves the turbine. This causes the fluid to pass trough the impeller & then push on the turbine vanes again with a helping force that aid rotation. The result is torque multiplication under certain condition. • Torque multiplication: in many torque converter the torque is more than double.e.g, 1.35N.m of torque entering the impeller, the turbine delivers more than 2.7N.m of torque to the transmission input shaft. Torque multiplication occurs only when the impeller turns faster than the turbine.
  • 14. Fluid flow within a torque converter. The stator redirects the fluid that is thrown out by the turbine, thereby improving efficiency.
  • 16. Fluid pumped into the turbine by the impeller not only creates rotary fluid flow but also vortex flow that increases the efficiency of the torque converter.
  • 17. STATOR ONE- WAY CLUTCH • As the vehicle approaches cruising speed, the turbine begins to catch up with the impeller (coupling point). • The fluid leaving the turbine is moving at about the same speed as the impeller. This fluid could pass directly into the impeller without stator action. In fact, the stator vane are now in the way. The fluid is striking the back sides of the stator vanes. • To allow the stator vanes to move out of the way, the stator mounts on a one- way clutch (overrunning clutch)
  • 18. One- way Clutch • A mechanical device that tranmits torque in one direction & permits free rotation in the opposite side. • When the speed difference between the impeller & the turbine is large, the fluid from the turbine tries to spin the stator backward. This causes the one- way clutch to lock the stator to its shaft. When the speed difference is small, the clutch unlocks & allows the stator to freewheel. 2 types of one way clutch are roller clutch & sprag type clutch.
  • 21. TORQUE CONVERTER CLUTCH (TCC) • Function: A lockup torque converter eliminates the 10% slip that takes place between the impeller and turbine at the coupling stage. The engagement of a clutch between the impeller and the turbine assembly greatly improves fuel economy and reduces operational heat and engine speed.
  • 24. • The lock- up torque converter (TCC) has a lock- up or clutch piston with a lining of friction material. • The piston or plate attaches to the turbine hub. • Isolator springs helps dampen the shock of engagement as the torque converter locks. They also dampen out the power pulse from the engine while the torque converter is locked.
  • 26. • The clutch is controlled by hydraulic valves, which are controlled by the PCM. The PCM monitors operating conditions and controls lockup according to those conditions. • When the converter is not locked (clutch disengage), fluid enters the converter and moves to the front side of the piston, keeping it away from the shell or cover. Fluid flow continues around the piston to the rear side and exits between the neck of the torque converter and the stator support. • During the lockup mode ( clutch engage), the switch valve moves and reverses the fluid path. This causes the fluid to move to the rear of the piston, pushing it forward to apply the clutch to the shell and allowing for lockup. Fluid from the front side of the piston exits through the turbine shaft that is now vented at the switch valve.
  • 27. • Reduction in engine speed and the elimination of the normal slippage in the torque converter improves fuel economy. • The torque converter clutch is released during rapid acceleration for maximum torque multiplication through the torque converter for best acceleration.
  • 29. • Revise a basic hydraulic circuit components:- a. Hydraulic pump b. Control valves (directional control) - Pressure relief valves - Pressure regulators - Shuttle valves - Check valves c. Actuators( Hydraulic cylinder, Swashplates, Hydraulic motor , hydrostatic transmission, Brakes) d. Reservoir e. Accumulators f. Hydraulic fluid g. Filters h. Tubes, pipes and hoses i. Seals, fittings and connections
  • 31. A/T GEAR- TRAIN • Gear-train consist of the following:- a. Planetary gearset: A compound epicyclic planetary gearset, whose bands and clutches are actuated by hydraulic servos controlled by the valve body, providing two or more gear ratios. b. Clutches and bands: to effect gear changes, one of two types of clutches or bands are used to hold a particular member of the planetary gearset motionless, while allowing another member to rotate, thereby transmitting torque and producing gear reductions or overdrive ratios. These clutches (overrunning clutch) are actuated by the valve body (see below), their sequence controlled by the transmission's internal programming.
  • 32. C. Valve body: hydraulic control center that receives pressurized fluid from the main pump operated by the fluid coupling/torque converter. The pressure coming from this pump is regulated and used to run a network of spring-loaded valves, check balls and servo pistons. The valves use the pump pressure and the pressure from a centrifugal governor on the output side (as well as hydraulic signals from the range selector valves and the throttle valve or modulator) to control which ratio is selected on the gearset; as the vehicle and engine change speed, the difference between the pressures changes, causing different sets of valves to open and close. The hydraulic pressure controlled by these valves drives the various clutch and brake band actuators, thereby controlling the operation of the planetary gearset to select the optimum gear ratio for the current operating conditions. However, in many modern automatic transmissions, the valves are controlled by electro- mechanical servos which are controlled by the electronic engine control unit (ECU) or a separate transmission control unit (TCU, also known as transmission control module (TCM).
  • 33. a. PLANETARY GEARS • Any planetary gearset has three main components: a. The sun gear b. The planet gears and the planet gears' carrier c. The ring gear • Each of these three components can be the input, the output or can be held stationary. Choosing which piece plays which role determines the gear ratio for the gearset.