Torque Converter Centrifugal Pendulum Absorber

A centrifugal pendulum absorber is a type of

Tuned mass damper A tuned mass damper (TMD), also known as a harmonic absorber or seismic damper, is a device mounted in structures to reduce mechanical vibrations, consisting of a mass mounted on one or more Damping ratio, damped springs. Its oscillation frequ ...

. It reduces the amplitude of a

Torsional vibration Torsional vibration is angular vibration of an object—commonly a shaft along its axis of rotation. Torsional vibration is often a concern in power transmission systems using rotating shafts or couplings where it can cause failures if not contr ...

in drive trains that use a combustion engine.

History

The centrifugal pendulum absorber was first patented in 1937 by R. Sarazin and a different version by R. Chilton in 1938. Generally, both Sarazin and Chilton are credited with the invention. Sarazin's work was used during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

by Pratt & Whitney for aircraft engines with increased power output. The power increase caused an increase in torsional vibrations which threatened the durability. This resulted in the Pratt & Whitney R-2800 engine that used pendulum weights attached to the crank shaft. The use of centrifugal pendulum absorbers in land vehicles did not start until later. Although internal combustion engines had always caused torsional vibrations in the drive train, the vibration amplitude was generally not high enough to affect durability or driver comfort. One application existed in tuned racing engines where torsional crank shaft vibrations could cause damage to the cam shaft or valves. In this application, a centrifugal pendulum absorber, the Rattler® absorber, is directly attached to the crank shaft. Although the design differs from that of Sarazin or Chilton, the Rattler® still follows the same physical principle. In 2010, centrifugal pendulum absorbers following the patents of Sarazin and Chilton were introduced in a BMW 320D. The reason for it was again the increase in torsional vibrations from higher power engines. In this case, the 4-cylinder diesel engine

BMW N47 BMW N47 is a four-cylinder common rail diesel engine that has many improvements over its predecessor, the M47. In 2014 it was replaced with the B47. First use The N47 engine debuted in March 2007 in the facelifted 1 Series BMW E87 and E81 and w ...

. Unlike the previous designs, the centrifugal pendulum absorber was not attached to the combustion engine but attached to a dual mass flywheel.

Function

The function of a centrifugal pendulum absorber is as with any tuned mass absorbers based on an absorption principle rather than a damping principle. The distinction is significant since dampers reduce the vibration amplitude by converting the vibration energy into heat. Absorbers store the energy and return it to the vibration system at the appropriate time. Centrifugal pendulum absorbers like tuned mass absorbers are not part of the force/torque flow. The centrifugal pendulum absorber differs from the tuned mass absorber in the absorption range. It is effective for an entire order instead of a narrow frequency range.

Modern Applications

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 co ...

s follow a development trend towards a reduction in the number of cylinders, increased energy output per cylinder and driving at lower engine speeds. This leads to an increased engine efficiency but causes the engine's torsional vibrations to increase. The vibrations lead to durability concerns as well as a comfort reduction for the passengers and have to be avoided through the use of

torsion damper Torsion may refer to: Science * Torsion (mechanics), the twisting of an object due to an applied torque * Torsion of spacetime, the field used in Einstein–Cartan theory and ** Alternatives to general relativity * Torsion angle, in chemistry ...

s and absorbers. This situation moves the balance between the cost of the centrifugal pendulum absorber technology and the benefit for the drive train efficiency. The following cars use centrifugal pendulum absorbers * BMW 320D * Mercedes E250 Diesel * Chevrolet Colorado Diesel * GM Products Equipped with the 2.7L L3B Engine * Chevrolet Corvette (C8)

References

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External links

Schaeffler Media Library - Centrifugal Pendulum Absorber
- video depicting a dual mass flywheel with a centrifugal pendulum absorber
EPI Crankshaft Torsional Absorbers
- centrifugal pendulum absorber on the crankshaft of an airplane engine
Engine History R-2800
- development of an engine crank shaft with centrifugal pendulum absorber Mechanical vibrations Pendulums Engine technology Mechanical engineering