Torque limiter

A torque limiter is an automatic device that protects mechanical equipment, or its work, from damage by mechanical overload. A torque limiter may limit the torque by slipping (as in a friction plate slip-clutch), or uncouple the load entirely (as in a shear pin). The action of a torque limiter is especially useful to limit any damage due to crash stops and jams.

Torque limiters may be packaged as a shaft coupling or as a hub for sprocket or sheave. A torque limiting device is also known as an overload clutch.

Disconnect types

Disconnect types will uncouple the drive, with little or no residual torque making its way to the load. They may reset automatically or manually.

Shear pin

A shear pin type sacrifices a mechanical component, the pin, to disconnect the shafts.

Synchronous magnetic

A synchronous magnetic torque limiter uses permanent magnets mounted to each shaft, with an air gap between. They are very fast acting, but may have more backlash than mechanical types. Because there is no mechanical contact between the two shafts, they are also used to transmit torque through a physical barrier like a thin plastic wall. On some models, the torque limit may be adjusted by changing the gap between the magnets.

Ball detent

A ball detent type limiter transmits force through hardened balls which rest in detents on the shaft and are held in place with springs. An over-torque condition pushes the balls out of their detents, thereby decoupling the shaft. It can have single or multiple detent positions, or a snap acting spring which requires a manual reset. There may be a compression adjustment to adjust the torque limit.

Many cordless drills incorporate this type of torque limiter in a planetary gearset. It may be a part of an assembly of multiple gearsets used to primarily reduce speed and multiply torque as well as perform ratio changes. The torque limiter is typically the last gearset in the transmission. It uses the planet carrier as the input with the sun gear as the output, and the annulus normally locked. A series of ball detents act on the annulus to lock it, allowing power to be transmitted from the planet carrier to the sun gear. When the torque transmitted through the gearset reaches a determinate amount, the torque acting on the annulus causes it to unlock from its ball detents and freely rotate, causing power to be diverted from the load on the sun gear to the annulus and thereby stalling the output until torque is reduced to an amount where the ball detents can lock the annulus again. This system equally limits torque in both directions of rotation and also works with the sun gear as the input. The compression of the ball detents (and therefore the amount of torque at which the limiter is utilized) is typically adjusted by means of a rotating collar accessible to the user which is indexed and held in place with its own separate ball detents.

Pawl and spring

This mechanical type uses a spring to hold a drive pawl against a notch in the rotor. It may feature automatic or manual reset. A compression adjustment on the spring determines the torque limit.

Torque limiting types

Torque limiting types will limit the torque by slipping (ie. letting the drive shaft run faster than the driven shaft.) Excess power is dissipated as heat. They don't need to be reset.

Friction plate

This type is similar to a friction plate clutch. Over-torque will cause the plates to slip. A simple example is found in a fixed-spool fishing reel, where the slipping torque is set by means of a large hand nut in order that the reel will turn and allow more line to unwind before the line breaks under the pull of a fish.

Magnetic particle

A magnetic particle clutch can be used effectively as a torque limiter. The torque setting fairly approximates a linear relationship with the current passing through the windings, which can be statically or dynamically set depending on needs.

Magnetic hysteresis

This type is non-synchronous in normal operation, so there is always some slippage.

See also

• Torque converter
• Transmission (mechanics)
• Clutch

References

External links

• Why Use a Torque Limiter?
• How does a Torque Limiter work?

This article about a mechanical engineering topic is a stub. You can help Wikipedia by expanding it.v · Categories: Mechanisms Mechanical engineering stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем написать реферат Desmond Kelly Buzz! Look at other dictionaries: torque limiter — A tool used in conjunction with a plug wrench which allows the controlled tightening of spark plugs by releasing automatically once a preset torque setting is reached …   Dictionary of automotive terms Torque — For other uses, see Torque (disambiguation). Classical mechanics Newton s Second Law …   Wikipedia Torque wrench — A torque wrench is a tool used to precisely set the torque of a fastener such as a nut or bolt. It is usually in the form of a socket wrench with special internal mechanisms. A torque wrench is used where the tightness of screws and bolts is… …   Wikipedia limiter — also See engine speed limiter rev limiter torque limiter …   Dictionary of automotive terms Clutch — For other uses, see Clutch (disambiguation). Rear side of a Ford V6 engine, looking at the clutch housing on the flywheel …   Wikipedia Motor soft starter — Examples of motor soft starters [1] A motor soft starter is a device used with AC electric motors to temporarily reduce the load and torque in the powertrain of the motor during startup. This reduces the mechanical stress on the motor and shaft,… …   Wikipedia Kawasaki Ninja ZX-10R — Infobox Motorcycle name = Kawasaki ZX 10R aka = manufacturer = Kawasaki production = 2004 present predecessor = ZX 9R successor = parent company = class = Sport bike platform = engine = 998 cc, 4 stroke, 4 cylinder, liquid cooled, DOHC, 4 valve… …   Wikipedia Suzuki TL1000S — Infobox Motorcycle name = Suzuki TL1000S aka = Tillis manufacturer = Suzuki production = 1997 2001 predecessor = successor = Suzuki SV1000S parent company = class = Sport bike platform = engine = water cooled DOHC 996 cm³ V twin transmission = 6… …   Wikipedia Slipper clutch — A slipper clutch (also known as a back torque limiter) is a specialized clutch developed for performance oriented motorcycles to mitigate the effects of engine braking when riders decelerate as they enter corners. They are designed to partially… …   Wikipedia Anti-Hopping-Kupplung — Eine Anti Hopping Kupplung (im angelsächsischen Raum: Slipper clutch oder back torque limiter) ist eine ursprünglich im Motorradsport und seit einigen Jahren auch in straßenzugelassenen Sportmotorrädern eingesetzte spezielle Kupplung, welche im… …   Deutsch Wikipedia 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”