A torque converter is a type of
fluid coupling
A fluid coupling or hydraulic coupling is a hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power. that transfers rotating power from a
prime mover
Prime mover may refer to:
Philosophy
*Unmoved mover, a concept in Aristotle's writings
Engineering
* Prime mover (engine), motor, a machine that converts various other forms of energy (chemical, electrical, fluid pressure/flow, etc) into energy ...
, like an
internal combustion engine
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...
, to a rotating driven load. In a vehicle with an
automatic transmission
An automatic transmission (sometimes abbreviated to auto or AT) is a multi-speed transmission used in internal combustion engine-based motor vehicles that does not require any input from the driver to change forward gears under normal driving c ...
, the torque converter connects the power source to the load. It is usually located between the engine's
flexplate A flexplate (or flex plate) is a metal disk that connects the output from an engine to the input of a torque converter in a car equipped with an automatic transmission. It takes the place of the flywheel found in a conventional manual transmission s ...
and the transmission. The equivalent location in a manual transmission would be the mechanical
clutch
A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...
.
The main characteristic of a torque converter is its ability to increase
torque
In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...
when the output rotational speed is so low that it allows the fluid coming off the curved vanes of the turbine to be deflected off the stator while it is locked against its one-way clutch, thus providing the equivalent of a
reduction gear
A gear train is a mechanical system formed by mounting gears on a frame so the teeth of the gears engage.
Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission ...
. This is a feature beyond that of the simple fluid coupling, which can match rotational speed but does not multiply torque and thus reduces power.
Hydraulic systems
By far the most common form of torque converter in
automobile transmissions
A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods.
The year 1886 is regarded as t ...
is the hydrokinetic device described in this article. There are also
hydrostatic
Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body "fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an imme ...
systems which are widely used in small machines such as
compact excavators.
Mechanical systems
There are also mechanical designs for
continuously variable transmission
A continuously variable transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. T ...
s and these also have the ability to multiply torque. They include the pendulum-based
Constantinesco torque converter, the
Lambert friction gearing disk drive transmission
The Lambert friction transmission (or friction disk drive or friction-drive transmission) was a mechanism devised and patented by John W. Lambert in 1904. It was a mechanical transmission that consisted of a friction wheel pressed against the b ...
and the
Variomatic
Variomatic is the continuously variable transmission (CVT) of the Dutch car manufacturer DAF, originally developed by Hub van Doorne. It is a stepless, fully-automatic transmission, consisting of a V-shaped drive-belt, and two pulleys, each o ...
with expanding pulleys and a belt drive.
Usage
*
Automatic transmission
An automatic transmission (sometimes abbreviated to auto or AT) is a multi-speed transmission used in internal combustion engine-based motor vehicles that does not require any input from the driver to change forward gears under normal driving c ...
s on
automobile
A car or automobile is a motor vehicle with Wheel, wheels. Most definitions of ''cars'' say that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, pe ...
s, such as cars, buses, and on/off highway trucks.
*
Forwarder
A forwarder is a forestry vehicle that carries big felled logs from the stump to a roadside landing. Unlike a skidder, a forwarder carries logs clear of the ground, which can reduce soil impacts but tends to limit the size of the logs it c ...
s and other heavy duty vehicles.
*
Marine propulsion systems.
* Industrial power transmission such as
conveyor
A conveyor system is a common piece of mechanical handling equipment that moves materials from one location to another. Conveyors are especially useful in applications involving the transport of heavy or bulky materials. Conveyor systems allow ...
drives, almost all modern forklifts,
winches
A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension of a rope or wire rope (also called "cable" or "wire cable").
In its simplest form, it consists of a spool (or drum) attach ...
,
drilling rig
A drilling rig is an integrated system that drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to drill wat ...
s,
construction equipment
Heavy equipment or heavy machinery refers to heavy-duty vehicles specially designed to execute construction tasks, most frequently involving earthwork operations or other large construction tasks. ''Heavy equipment'' usually comprises five e ...
, and
railway locomotive
A locomotive or engine is a rail transport vehicle that provides the motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, motor coach, railcar or power car; the us ...
s.
Function
Theory of operation
Torque converter equations of motion are governed by
Leonhard Euler
Leonhard Euler ( , ; 15 April 170718 September 1783) was a Swiss mathematician, physicist, astronomer, geographer, logician and engineer who founded the studies of graph theory and topology and made pioneering and influential discoveries in ma ...
's eighteenth century turbomachine equation:
: