How does a torque converter work?
Discussion
automatic gearboxes = black art and pixies
wikipedia says
http://en.wikipedia.org/wiki/Torque_converter
A torque converter has three stages of operation:
Stall. The prime mover is applying power to the impeller but the turbine cannot rotate. For example, in an automobile, this stage of operation would occur when the driver has placed the transmission in gear but is preventing the vehicle from moving by continuing to apply the brakes. At stall, the torque converter can produce maximum torque multiplication if sufficient input power is applied (the resulting multiplication is called the stall ratio). The stall phase actually lasts for a brief period when the load (e.g., vehicle) initially starts to move, as there will be a very large difference between pump and turbine speed.
Acceleration. The load is accelerating but there still is a relatively large difference between impeller and turbine speed. Under this condition, the converter will produce torque multiplication that is less than what could be achieved under stall conditions. The amount of multiplication will depend upon the actual difference between pump and turbine speed, as well as various other design factors.
Coupling. The turbine has reached approximately 90 percent of the speed of the impeller. Torque multiplication has essentially ceased and the torque converter is behaving in a manner similar to a simple fluid coupling. In modern automotive applications, it is usually at this stage of operation where the lock-up clutch is applied, a procedure that tends to improve fuel efficiency.
wikipedia says
http://en.wikipedia.org/wiki/Torque_converter
A torque converter has three stages of operation:
Stall. The prime mover is applying power to the impeller but the turbine cannot rotate. For example, in an automobile, this stage of operation would occur when the driver has placed the transmission in gear but is preventing the vehicle from moving by continuing to apply the brakes. At stall, the torque converter can produce maximum torque multiplication if sufficient input power is applied (the resulting multiplication is called the stall ratio). The stall phase actually lasts for a brief period when the load (e.g., vehicle) initially starts to move, as there will be a very large difference between pump and turbine speed.
Acceleration. The load is accelerating but there still is a relatively large difference between impeller and turbine speed. Under this condition, the converter will produce torque multiplication that is less than what could be achieved under stall conditions. The amount of multiplication will depend upon the actual difference between pump and turbine speed, as well as various other design factors.
Coupling. The turbine has reached approximately 90 percent of the speed of the impeller. Torque multiplication has essentially ceased and the torque converter is behaving in a manner similar to a simple fluid coupling. In modern automotive applications, it is usually at this stage of operation where the lock-up clutch is applied, a procedure that tends to improve fuel efficiency.
HustleRussell said:
Secondary question- what's the difference between a torque converter and a fluid coupling? I understand how a fluid coupling works...
I believe the key difference is that the "stator" is essentially a very clever piece of engineering which lives inside a fluid coupling, turning it into a torque converter. It is machined in such a way that transmission fluid is deployed highly effectively as it circulates inside and it can actually multiply the torque of the engine by as much as 2 or 3 times, notably when moving off from rest. This is part of the reason dragsters tend to have auto boxes.doogz said:
That's not a bad link, thanks for sharing.Does the E46 transmission feature a "lock up clutch"?
mrmr96 said:
Does the E46 transmission feature a "lock up clutch"?
Every recent auto of any quality features a lock-up clutch.If you drive a 5-speed auto and listen/watch the rev counter carefully you will hear/see the transmission work through its ratios. And Hey Presto! It will sound/look as though you have a 6-speed! The transmiision will work through its 5 ratios and then at the appropriate speed you will think you hear/see another gearchange. That's just the clutch locking up and engine rpm will drop slightly as the mechanical clutch eliminates the small loss in the torque converter.
Ozzie Osmond said:
mrmr96 said:
Does the E46 transmission feature a "lock up clutch"?
Every recent auto of any quality features a lock-up clutch.If you drive a 5-speed auto and listen/watch the rev counter carefully you will hear/see the transmission work through its ratios. And Hey Presto! It will sound/look as though you have a 6-speed! The transmiision will work through its 5 ratios and then at the appropriate speed you will think you hear/see another gearchange. That's just the clutch locking up and engine rpm will drop slightly as the mechanical clutch eliminates the small loss in the torque converter.
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