Patent ID: 7484434

Claim:
A torsional vibration damper comprising: a primary mass adapted to be coupled to an engine crankshaft for rotation about a rotational axis of the engine crankshaft, the primary mass defining a substantially ring-shaped chamber that is divided into at least two portions; a secondary mass relatively rotatably connected to the primary mass and connectable with a clutch; and a damping unit for coupling the primary and secondary masses to each other wherein the damping unit comprises; a plurality of coil springs situated in series and disposed one after the other within the divided portions of the ring-shaped chamber; a pair of end guides slidably disposed within each divided portion of the ring-shaped chamber and supporting outer ends of the coil springs among a plurality of elastic members; and a friction member slidably disposed between neighboring elastic members, the friction member being configured to be rubbed against the primary mass in response to compressions of the coil springs such that a friction force is generated in proportion to a relative rotation between the primary and secondary masses; wherein the friction member comprises: an outer guide provided with a first protrusion extending toward a center portion of the primary mass such that a first slanted surface and a second slanted surface are formed on both sides of the first protrusion; an inner guide disposed to face the outer guide and provided with a second protrusion extending toward the outer guide such that a third slanted surface and a fourth slanted surface are formed on both sides of the second protrusion; a first operator disposed between the outer and inner guides, one end of the first operator being elastically supported by one of the plurality of the coil spring, and a first slanted portion respectively contacting the first slanted surface of the first protrusion and the third slanted surfaces of the second protrusion, the first slanted portion being provided on the other end of the first operator, wherein the first slanted portion and the first and third slanted surfaces are linear; and a second operator disposed to face the first operator between the outer and inner guides, one end of the second operator being elastically supported by the other of the plurality of the coil spring, and a second slanted portion respectively contacting the second slanted surface of the first protrusion and the fourth slanted surfaces of the second protrusion, the second slanted portion being provided on the other end of the second operator, wherein the second slanted portion and the second and fourth slanted surfaces are linear, and wherein a width of the first protrusion becomes smaller as it becomes closer to the center portion of the primary mass and a width of the second protrusion becomes smaller as it becomes more distant from the center portion of the primary mass.