How Does a Torque Converter Work in Automatic Transmissions?

[robotlab]

Hello,
New poster, Re: Torque Converters (automotive drivetrain component.)
1) Can anyone briefly explain the theory of operation of the device?
2) Why is it not present in vehicles with manual shift?
3) Is this a fluid power device?
4) Any on-line resources available for good info, drawings?

Thanks in advance for your time.

 

[S_Happens]

1) It's a modified fluid coupling transferring rotational energy from a pump to a fluid to a turbine, which allows the engine to turn the transmission. This means the vehicle can come to come to a stop (or operate in most any situation with the engine and transmission at different rotational speeds) without manually disengaging the two (ie a clutch).
2) With a manual clutch/pressure plate the driver DIRECTLY controls whether the transmission is "coupled" to the engine/flywheel, so there is no need for a torque converter.
3) I'm not sure about fluid power devices, but it's basically a fluid coupling that can be mechanically coupled at some times. A fluid is the medium through which energy is transferred from the pump to the turbine (when not mechanically coupled).
4) I'd hate to think that you wouldn't check wikipedia, but it is a very good basic write up so here's the link
http://en.wikipedia.org/wiki/Torque_converter"

I have write ups saved on my personal computer, but I'd have to dig them up, see if they are worth reading, and then possibly host them.

 

[Ranger Mike]

Pretty close..automatic transmission have two major components, the torque converter and the transmission
the torque converted is mechanically attached to the engines crankshaft via a flex plate. the other end goes into the input shaft of the automatic transmission. The simple fluid coupling or torque converter has a pump located near the center of the revolving wheels inside the converter. this pump distributes fluid (Automatic Transmission Fluid -ATF..light weight oil) outward through vanes in the torque converted stamped steel housing. As engine rpm drops, below a certain point, near idle speed, hydraulic pressure is not enough to overcome static weight of the car..no movement. As RPMs go up, pressure goes up and ATF thrown across reaction vanes begin to turn the transmission smoothly wit h a CERTAIN AMOUNT OF SLIPPAGE. At High Revs the driving and driven members lock up for a 1: lock up ration..In later years over drive goes to 1/2:1 lock up ration.The Transmission has a set of planetary gear sets connected by clutch packs producing final gear ratios and output spline shaft that connects to the standard drive shaft and hence rear end..or now a days, front wheel drive half shafts and front wheels.

This technology as 1950's vintage ..early models were real slush boxes but no clutch was required and lots were sold to..( I will try to be delicate ) married couples cause the clutch / stick shift thing was not popular with the wife...
Chrysler really upped the Automatic scene in the early 1960s when they Coupled huge 426 cube engines to their bullet proof automatics..one technique soon outlawed by the NHRA as to " Banzi " launch the Super Stock Dodges and Plymouths..i.e. Rev the engine to 7000 RPM in Neutral and punch 1st gear button..(back then they had push buttons not console levers or steering wheel levers to select gears)...it really launched the car with huge amounts of torque multiplication, off the Line...or a few Banzis..'til things broke and AFT was all over the drag strip

One thing we kids used to do was write Js on the country back roads..this was where you put the family grocery getter into Reverse and backed it up about 10 feet at high speed then slammed the trans into low gear..really shocked the valve modulator and torque converter..this was absolute torture to the old 6 cylinder POS used to take you to school..the tire patch was a perfect little J left on the asphalt..
anyway.. now you know