A torsional vibration damper, for example a twin mass flywheel (10), has an input element (11) and an output element (12) which are relatively rotatable against the action of a damping means which includes a plurality of linkages (40). Each linkage includes a plurality of interconnected links (41, 42), at least one of which is flexible in an axial sense relative to the remainder of the damper to accommodate forces applied to the flexible link as a result of relative tilting of the damper elements (11, 12) during use of the damper. Various designs of generally radially extending flexible bob weight links (41) and additional connecting links (42) are disclosed.

A damping device (10) includes co-axially arranged first and second parts (11, 12) which can rotate relative to each other by a limited amount about an axis (15) of the damping device. The device also includes at least one linkage device (40A) comprising an anchor link (43) pivotally connected via a first pivot (44) to the first part (11) and having a torque transmitting connection (41A) with the second part (12). The linkage device (40A) acting to resist relative rotation of the first and second pars (11, 12). There is also provided a resilient means in the form of coil spring (66A) which acts generally circumferentially between the linkage device (40A) and the first part (11) to resist relative rotation of the first and second parts (11, 12).

A twin mass flywheel for a vehicle comprising two coaxially arranged relatively rotatable masses interconnected by a plurality of pivotal linkages. Each linkage comprises a first link pivotally connected to one flywheel mass, a second link pivotally connected to the other flywheel mass and a pivot joining the links to move radially outwardly. A resilient torque member in each common pivot operable after a predetermined rotation between the flywheel masses to resist said relative rotation. A variable hysteresis friction damping assembly, whose resistance to relative rotation changes as the relative angle of rotation is altered, acts between the flywheel masses. The damping assembly can be provided by two friction damping plates which operate at different stages of rotation. The relative rotation may be limited by a stop member on at least one of the flywheel masses which abuts an abutment surface on the other flywheel mass. The abutment surface can be resilient for cushioning abutment by the stop member.

A torsional vibration damper comprising an input member for connection with a vehicle engine and an output member for connection with a vehicle transmission, the members being mounted for limited relative rotation about a common axis against a damping means comprising one or more circumferentially acting compression springs. Each spring acts between a first abutment formed as an integral part of the input member and a second abutment formed as an integral part of the output member. The damper may also include one or more elastomeric springs or blocks which are subjected to compression in end zones of the relative rotation of the input and output members. Other inventive features of the damper include support members for avoiding fouling of the elastomeric springs or blocks by the compression springs and the use of cantilevered pivot pins for the connection of bob-weight connecting linkages connected between the input and output members. Various friction damping arrangements are also disclosed which can be speed and/or displacement dependent. A method of assembling the damper is also disclosed.

A torsional vibration damper, particularly for use between the engine and the transmission of the power train in a motor vehicle, including two flywheels rotatable relative to each other against the opposition of a first energy storing device employing, for example, one or more coil springs and a second energy storing device, which is carried by one of the flywheels, which operates in parallel with the first energy storing device and which opposes rotation of the two flywheels relative to each other. In order to isolate the irregularities of movement of the first flywheel (such as vibrations which develop while the engine is in operation) from the second flywheel, the second energy storing device (such as a snap spring or a set of diaphragm springs) is coupled to the flywheels in such a way that the second flywheel develops a degressive action only when the first flywheel is caused to move through relatively small angles (especially between 1.degree. and 10.degree.) but not when the angles are larger (especially larger than 10.degree.).