190303B Flashcards
Torque Converter Fundamentals and Service
What do torque converters act as?
coupling devices, increase torque received from engine
What is the principle behind hydrodynamic drives?
energy transfer from one component to another through fluid motion
what are other names for hydrodynamic drive?
fluid couplings or fluid clutches
What is the principle behind hydrostatic drives?
use fluid under pressure to achieve drive
Energy transfer in a fluid coupling depends on three things:
Volume, Velocity, Viscosity Rating
What is volume controlled by in an energy transfer?
physical size of impeller (pump) vane size, number of vanes, structure of vanes
What is velocity controlled by in an energy transfer?
physical size of converter, actual size of the vanes and angles of vanes, speed of impeller
What are the two elements that make up a fluid clutch?
impeller and turbine
how does an impeller and turbine work as a coupling device?
transmits torque from an engine to driveline or directly to a tranny through moving fluid (kinetic)
What is kinetic energy?
energy of motion
how is kinetic energy created in a fluid coupler?
from the impeller
what energy conversions does the turbine create?
kinetic to mechanical
Where does the impeller receive torque from>
the engine flywheel, driven by flywheel.
What causes the oil brought into the impeller to be moved outward?
centrifugal force
what energy conversions does the impeller create?
mechanical to hydraulic/fluid energy
Advantages of fluid couplers?
No mechanical connection
Shock absorption (created from sudden engine torque)
Gradual start up of a load
Where is slippage the highest in a fluid coupler?
at low speeds
why does slippage occur?
from the use of oil as a torque transfer medium
Disadvantages of fluid couplers?
Efficiency lost from slippage
Slippage creates heat
Can’t get to a 1:1 ratio bc of slippage
Fluid couplings can transmit torque, but can’t increase or multiply
Why does a fluid coupling unit not transfer 100% of the input torque?
bc both members in a fluid coupling have straight radial blades
All torque converters are fluid couplings, but
all fluid couplings are not torque converters
What is vortex flow?
flow of oil from impeller to turbine, back to impeller. circular movement like a spiral
When does vortex flow happen?
when turbine is turning at a lower speed than the impeller.
characteristics of vortex flow?
high heat, low output speed, high torque
what phase is vortex flow?
converter
What is rotary flow?
oil flows in same direction as the impeller is turning.
When does rotary flow happen?
when impeller and turbine are turning at almost the same speed. when impeller, turbine, and oil move together
characteristics of rotary flow?
low heat, high output speed, low torque
what phase is rotary flow?
coupling
Where is a split guide ring?
in the impeller and turbine, its a half shaped donut in the middle of the unit above the vanes (oil passes beneath it)
Purpose of a split guide ring?
prevent turbulence within the unit (smooths and directs oil flow)- laminar flow
What is a torque converter?
a fluid coupler with a third element: a stator
Can a torque converter multiply torque received by engine?
yes no shit
What are the energy conversions when using a torque converter?
mechanical (engine), into kinetic fluid energy, into mechanical energy (tranny or driveline)
What is a remote torque converter?
a torque converter not mounted directly to the engine, uses a short drive shaft in-between
what is the impeller element often referred to as?
pump element
How is the impeller connected?
to the engine flywheel (input). turns whenever flywheel is turning
purpose of having angled vanes on the impeller?
increases force and accuracy of fluid flow onto vanes in turbine element
how is the turbine connected?
bearing mounted in rear of torque converter housing, drives output shaft. physically sits closer to the flywheel
What’s another name for a stator?
reaction member
purpose of a stator?
change direction of oil flow to assist in torque multiplication
what does increasing torque multiplication do for the torque converter?
increases efficiency
how does the change in direction allow kinetic energy to be used?
if energy isn’t used in first pass of oil, that kinetic energy in oil goes back to impeller and gains even more energy as it’s flung around again to increase the velocity of the oil
what does increasing the velocity of oil do in relation to torque?
increases engine torque by approx 2.00:1 to 3.00:1 ratio
what does the exact amount of torque multiplication depend on in a stator?
angle of the vanes in the elements
What torque condition is happening when the impeller rotates faster than the turbine and the stator is stopped?
torque multiplication
how does torque multiplication happen in a torque converter?
kinetic energy in the fluid leaving the stator gets sent back to the impeller and increases torque. recirculating fluid with kinetic energy
why do you need an overrunning clutch?
to prevent oil from turning the stator in the opposite way of impeller motion, reducing the torque
two types of stators?
fixed and freewheeling
how is a fixed stator positioned in the housing?
attached to converter housing stub shaft, does not move. splined to a sleeve.
can a fixed stator achieve rotary flow?
no. that means its a single phase converter
what is a freewheeling stator?
a stator with an overrunning clutch.
what stage is a freewheeling stator turning at and stopped?
freewheels in coupling phase
stationary in converter phase (torque increase required)
When does the freewheeling stator lock up?
when the turbine speed is lower than impeller speed
how many conditions does a freewheel stator have?
two (locked and freewheeling) so its a two phase converter
what does a lockup clutch do?
mechanically connects turbine and impeller to eliminate small amount of slippage.
what is a benefit of using a lockup clutch?
1:1 drive ratio for fuel efficiency.
when should direct drive be used?
when machine is empty, on level ground, or at high speed low torque.
how can the lockup clutch be activated?
manually, pneumatically, hydraulically, electrically
how does a lockup clutch work?
friction surface area pressing together, actuated by hydraulic pressure at the back of the piston pushing them to the turbine
When is maximum ratio accomplished in a torque converter?
at stall
when is minimum ratio accomplished in a torque converter?
when impeller and turbine are at approx the same speed
What is a phase?
relationship of the impeller and turbine relative to energy transfer
what is a stage?
number of times oil strikes the turbine before returning to impeller
3 phases?
converter, coupling, lockup
What is the converter phase?
occurs when turbine is slower than impeller (vortex flow)
what is the coupling phase?
turning turns approx same speed as impeller (rotary flow)
what is lockup phase?
turbine and impeller are locked to each other mechanically
how are stages classed?
number of turbine elements
what kind of stators do multi-stage converters have?
fixed, always in converter (vortex) phase
what is stall speed?
turbine stopped, impeller turning at rated engine speed, or when turbine and impeller at at the greatest difference in speed
What is a downside of stall?
high heat
a coupling phase, converter phase, and stall speed are considered to be what in a torque converter unit?
functional changes
purpose of a variable capacity torque converter?
increase or decrease torque capacity within its ratio range according to torque demand
3 types of variable capacity converters?
multiple impeller, multiple turbine, variable pitch stator
how does a multiple impeller work?
first impeller attaches to flywheel, constantly driven, other freewheels. second one controlled when piston pushes 2 together
when would you use the multiple torque impeller?
for when you need high torque
how is the benefit of using a multiple impeller achieved?
inner impeller send oil to other impeller, more circumference. oil needs to go faster to reach outer blades, so a change in velocity is created
how do multiple turbines work?
2 turbines connect with an overrunning clutch. only use 2 when needing high torque
How do variable pitch stators work?
changing angle of stator vanes changes amount of vortex flow= more or less torque
when is the highest torque produced on a variable pitch stator?
when its in the open position. smaller piston pushes bell crank and opens vanes= proper vortex flow
what does the charge pump do on a torque converter circuit?
deliver oil to converter and tranny
driven by impeller or off flywheel
what does the converter inlet relief valve do?
protects converter from excess pressure
main pressure control
what does the pressure regulating valve do?
maintains working pressure in converter.
normally closed but always open
prevents cavitation and aeration
on converter outlet
where is the temp sender gauge located?
converter outlet port
what kind of oil should be used in a converter?
light oil. ATF, or diesel (early models)
what happens if oil is too heavy in a converter?
it could cause converter to not use a gradual start up method.
do dry housings have PTO’s?
no, wet housings do
Why do you need a scavenge system on a wet housing?
to prevent oil level from contacting outer circumference of converter= loss of power and heat
2 types of scavenging used on wet housings?
gravity (if converter housing above tranny)
pump (if converter housing and tranny are on same plane) driven by impeller
What does the torque divider combine?
single stage torque converter and a planetary gear set
how does a torque divider work?
splits varying percentages between converter and planetary (30% torque, 70%planetary)
functions of a torque divider?
provide auto clutching
multiply engine torque based on output shaft load
absorb power train shocks
in a torque divider, impeller connects to the:
and the turbine connects to the:
the planetary carrier connects to the:
sun gear
ring gear
output shaft
the difference of speed between the impeller (sung gear) and the turbine (ring gear) determines?
output shaft speed
on a torque divider, load or resistance on the output shaft determines the speed and direction of the?
turbine
power transmitted to the output shaft of the torque divider is controlled by ______ that affect the planetary gear set?
conditions
the amount of power applied to the input members will determine the speed and torque transmitted to the output shaft
T or F
True
What is happening in a torque divider when the engine is idling and output shaft stalled?
sun gear + impeller driven at engine speed, vortex flow not fast enough to make turbine + ring gear reactionary. the carrier is stalled, the planets act like reverse idlers. ring gear + turbine are idling in reverse direction bc of the sun gear.
what is happening in a torque divider when the engine is wide open throttle and output shaft speed stalled?
max engine torque multiplication. planet carrier gets max torque from sun gear but stays stationary. impeller at max speed. turbine rotates in reverse. lots of vortex flow
What type of housing does a torque divider have and where does that oil come from?
wet housing, comes from engine driven charge pump
2 types of mounting options for torque converters?
engine (integral) and remote
what does mounting the torque converter directly to the engine reduce?
the need to check proper torque converter/engine alignment
what torque converter gear design can be used to accommodate differences in misalignment between engine and torque converter?
rubber block tooth construction
since torque is transmitted through a fluid instead of a solid device, what vibrations are absorbed within the torque converter and are not passed on to the other powertrain components?
torsion vibrations
Benefit of remote mounting a torque converter?
better access to torque converter and transmission, don’t need to disturb engine/engine mounts when removing converter/tranny
what is critical when installing or replacing a remote mounted torque converter?
proper driveline alignment
What is the first step when determining torque converter problems?
installing pressure and temp gauges at converter/tranny
where is the greatest amount of torque multiplication found?
when impeller is at greatest speed and turbine is stopped (stall condition)
What gear is the tranny in when performing a stall test?
the highest gear
what will happen if you perform a stall test in a low gear?
tranny/driveline damage from high amount of torque
what are 3 conditions that indicate a torque converter problem?
high stall speed
low stall speed
overheating
what does high stall speed indicate?
converter is not multiplying torque as required, or forward clutch in tranny is slipping
what does a slipping tranny clutch also cause?
high temp, look at temp when stall testing.
what does a low stall speed indicate?
engine not developing enough torque required, or a slipping stator overrunning clutch
what does overheating indicate?
operator is dumb and is in too high of a gear for the application
plugged converter oil cooler or fault charge pump
oil low from leakage
high oil level
what should you be aware of when removing a torque converter and tranny?
ensuring the torque converter doesn’t fall off the tranny shaft
why should you check crankshaft end play after reinstalling a torque converter?
to ensure torque converter mounted properly, hasn’t end loaded crankshaft
What are some other checks to make when reinstalling a torque converter?
flywheel housing bore diameter
flywheel housing bore eccentricity
flywheel housing face squareness
crankshaft hub eccentricity
crankshaft hub face squareness
flex plate flatness
converter axial location
crankshaft hub pilot diameter
shift linkages
when the output shaft on a torque divider is stalled and the engine is at max RPM the turbine is:
turning in reverse
