Clutch Disc

Torsion damper

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Torsion dampers have the task of damping vibrations between the engine and transmission.

Unlike electrical motors and turbines, internal combustion engines do not deliver a constant torque. The constantly changing angular speeds of the crankshaft produce vibrations that are transmitted via the clutch and transmission input shaft to the transmission, where unpleasant rattling noises are the result. Torsion dampers are designed to minimize these vibrations between engine and transmission.

The constant reduction in flywheel mass and the lighter construction of modern vehicles increase these undesirable effects. Accordingly, every vehicle today must be subjected to special tuning, which has led to a wide variety of dampers and designs. Chart 1 therefore shows only a few typical designs.

On the right of the illustration, three types of torsion damper are displayed.

They operate according to the following basic principle:

The hub (15), supported on bushes between the drive disc (17) and the retainer plate (18), is spring-loaded via the hub flange (19) and the damper springs (10-13) against the drive disc and the retainer plate, so that under load large or small angular motion is achieved. The spring compression is dampened by a friction assembly (7, 8, 9, 20). The transfer torque of the damper must always be greater than the engine torque, to prevent the hub flange (19) from striking against the stop pin (6).

In modern vehicle construction, two- and multiple-stage characteristic curves are often required. The stages are produced by springs with various spring rates and variously sized windows. The friction assemblies also differ largely due to different friction and spring washers. The characteristic curves are usually not symmetrical, but display in the direction of drive a steeper line with a higher stop torque than in the ‘coast’ or ‘overrun’ direction.
Single-stage friction control design with spring washer for uniform friction, 2-stage torsion damper

The upper torsion damper has a simple friction device with a friction washer producing constant friction and a two-stage characteristic curve. The hub flange (19) runs between the retainer plate (17) and cover plate (18), and is supported by the main damper springs of the 1st stage (12) and 2nd stage (13). The hub flange (19) can be turned up to 16 degrees against the retainer plate (17) and cover plate (18) before striking the stop pin (6). In this way the coil springs lying in the windows of the clutch and retainer plates, which have different spring rates, are tensioned. Vibration is converted to friction through the spring washer (7).


Single-stage friction control design with spring washer for uniform friction, 2-stage torsion damper
The upper torsion damper has a simple friction device with a friction washer producing constant friction and a two-stage characteristic curve. The hub flange (19) runs between the retainer plate (17) and cover plate (18), and is supported by the main damper springs of the 1st stage (12) and 2nd stage (13). The hub flange (19) can be turned up to 16 degrees against the retainer plate (17) and cover plate (18) before striking the stop pin (6). In this way the coil springs lying in the windows of the clutch and retainer plates, which have different spring rates, are tensioned. Vibration is converted to friction through the spring washer (7).


Single-stage friction control design with 2 friction washers for uniform friction, 2-stage torsion damper
The middle torsion damper is designed similarly to the upper one, but is additionally provided with two friction washers (8). They are made of either organic material or plastic. Organic friction washers offer higher frictional coefficients, while plastic friction washers provide less friction, but excellent wear resistance.


Torsion-angle-dependent, 3-stage friction control design, 2-stage main damper, separate 2-stage idle damper
The lower torsion damper has a 3-stage friction assembly dependent on the torsion angle, a two-stage main damper and a separate two-stage idle damper. The separate idle damper, consisting of an idle damper flange (24) and idle damper retainer plate (25) with idle damping springs of the 1st stage (10) and 2nd stage (11), is primarily used in cars with diesel engines. It acts at lower engine torque’s and dampens during idling. The three friction washers (8) of the 3-stage friction assembly begin to act at different torsion angles. The 2-stage main damper (12) and (13) operates similarly to the above-described systems.