Rotary shafts – gudgeons – housings – and flexible couplings for ro – Torque transmitted via flexible element – Coil spring
Reexamination Certificate
1998-10-28
2002-07-09
Binda, Greg (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Torque transmitted via flexible element
Coil spring
C464S083000, C192S214100
Reexamination Certificate
active
06416416
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a torsional vibration damper, especially for clutches that consists of a primary body and a secondary body.
Such a torsional vibration damper is e.g. described in EP 0 718 518 A1 which consists of a primary body and secondary body between which is located an arrangement of tangentially-acting spiral springs and tensioning bodies so that the primary body and secondary body can be rotated up to a maximum angle with a torsional characteristic determined by the spring arrangement. The tensioning bodies consist of cylinders and pistons that enclose a cavity which is filled with a cylindrical body of elastoplastic material whose diameter is less than the inner diameter of the cavity and is dimensioned so that it completely fills the cavity after the piston travels an initial, short path. The springs and the tensioning bodies serve as internal dampers to prevent rotary vibrations in the drive train excited by a drive.
DE 41 28 868 A1 describes a torsional vibration damper for similar clutches in which the primary body and the secondary body are only connected by tangentially active spiral springs. A friction ring is provided as the actual damping moment that becomes effective only after a certain angle of rotation is traversed between the primary and secondary bodies.
These prior art systems have the disadvantage that they only encompass part of the working spectrum of a drive but are ineffective in the additional load range. The problem is that the spring force and damping must correspond to the transmitted torque and speed for the load range while only a slight spring force and basically no damping are required to allow the clutch to be disengaged during idling. In the critical speed range, i.e., at speeds within the range the natural frequency, very strong damping is required since the angular acceleration would otherwise be too great in contrast to the primary side. This speed range is passed through primarily when the engine is started and when the load changes. In case of resonance, dynamic moment can arise that is a multiple of the nominal moment.
SUMMARY OF THE INVENTION
It is an object of the invention to present a torsional vibration damper especially for clutches where the damping characteristic can be optimally adapted.
For a solution, the invention suggests a torsional vibration damper consisting of a primary body and secondary body with a drag element that comprises at least one friction element with at least one pressure device, at least one catch and at least one elastic element.
The friction element can either interact with the primary body or the secondary body, and the catch drives the remaining body.
The pressure device is advantageously arranged so that a force acting on the pressure device increases the friction between the friction element and either the primary body or the secondary body. As will be explained in greater detail below, the pressure device can be formed by a friction ring edge or by an expanding ring that is situated in reference to the friction ring, and it interacts with the elastic element so that a force exerted by the elastic element on the pressure device, i.e., on the friction ring edge or the expanding ring increases the friction of the friction element with the primary or secondary body. Hence the friction caused by the friction element depends on the force exerted on the elastic element and hence on the angle of rotation between the primary and secondary bodies.
The arrangement according to the invention allows the damping characteristic to be suitably adapted, especially when large forces are exerted.
The elastic element advantageously has a rubber-like element in a cavity. The damping characteristic of the torsional vibration damper according to the invention can be advantageously influenced under large and small forces or angles of rotation. Under small forces or angles of rotation, the rubber-like element acts like an elastic spring. If the rubber-like element is further compressed until it fills the cavity, the elastic element consisting of the cavity and rubber-like element as if it enclosed a hydraulic liquid. In this state, the elastic element can counter substantially higher forces than prior-art torsional vibration dampers.
Particularly when the elastic element is tangentially compressed by a relative movement between the primary and secondary bodies, it is advantageous when the rubber-like element is without play in a tangential direction in the cavity. The elastic effect of the rubber-like element then begins immediately.
A particularly simple and hence reliable construction arises in this case when the cavity is delimited radially by a pressure device. The tangential compression of the rubber-like element determines its radial and axial expansion. The rubber-like element can act radially on the pressure device and hence increase the friction between the friction element and either the primary or secondary body. If there is also an axially-acting pressure device, it is also correspondingly acted upon by force.
The volume ratio of the cavity to the rubber-like element and their dimensions can adjust the behavior of the drag element depending on the angle of rotation between the primary and secondary bodies. It is possible in particular to select a rubber-like element that radially fills the cavity at a few sites when relaxed. Upon axial compression of the rubber-like element, slight, direct force is transmitted to the radial pressure device. Likewise, the rubber-like element can be axially designed to exert a selected force on an axial pressure device.
Of course the cavity does not have to be fully enclosed. It is sufficient for the elastic element or rubber-like element to be securely held, or for the edge of the cavity to hold the rubber-like element in the cavity so that the elastic element cannot be excessively pressed out of the cavity.
The force on the rubber-like element can result from a reduction in volume of the cavity due to a relative rotational movement between the primary and secondary bodies. In particular, it is advantageous when the reduction in volume is tangential since such a movement corresponds to the relative movement between the primary and secondary bodies, and the force does not have to be diverted. In particular, axial force is avoided between the primary and secondary bodies.
Independent of this, the torsional vibration damper consisting of a primary body and secondary body can include a drag element that has at least one friction element with at least one essentially tangential stop, at least one essentially tangential catch and at least one elastic element that acts tangentially between the stop and catch, whereby the friction element either interacts with the primary or secondary body, and the catch drives the other cited body.
The tangentially-acting arrangement of the elastic element between the stop of the friction element and the catch allow an optimum adaptation of the damping characteristic, i.e., the rotational characteristic caused by the friction element even when the angle of rotation between the primary and secondary bodies is very small. In particular, the noise that arises in clutches upon load changes when idling caused by very small forces can be more effectively avoided in this manner in contrast to prior art clutches.
The pressure device can be designed so that it acts radially. This has the advantage that the force that acts radially on the pressure device is captured by the torsional vibration damper, and no axial force acts on the other components such as the clutch. This advantage can be attained by using a friction element with a friction surface which has a surface component that extends radially outward.
To attain a minimum friction between the friction element and the primary or secondary body even when the pressure device is not acted on by the elastic element, the friction element can be a pretensioned spring. In particular, this increases adaptability in the low load range.
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Heidingsfeld Dietmar
Rohs Hans
Rohs Ulrich
Binda Greg
Day Ursula B.
Feiereisen Henry M.
Rohs-Voigt Patentverwertungs-gesellschaft mbH
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