Torsion damping mechanism with auxiliary mass

Details Torsion damping mechanism with auxiliary mass Torsion damping mechanism with auxiliary mass

2001-10-05

2003-03-18

Browne, Lynne H. (Department: 3629)

Rotary shafts, gudgeons, housings, and flexible couplings for ro

Torque transmitted via flexible element

Coil spring

C192S03000R, C074S574300

Reexamination Certificate

active

06533665

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a torsion damping mechanism with frictionally connected auxiliary mass.
2. Description of the Related Art
Torsion damping mechanisms are used to reduce variations or peaks in the torque of a drive unit and thus to give the drive shaft behind the torsion damping mechanism a more uniform torque curve. Torsion damping mechanisms of this type are used in clutch mechanisms, for example, and in dual-mass flywheels. A torsion damping mechanism consists of an input area, usually disk-like in shape, on which torque is exerted via the peripheral areas, and an output area, also usually disk-like in shape. In the case of dual-mass flywheels, the output side and the input side are each provided with a flywheel, which is connected to the disk-shaped area such as a hub disk. The flywheel on the output side is usually connected to a downline clutch mechanism. In the case of pure clutch mechanisms, the disk-shaped output area is connected to a hub, which can drive an output drive axle. The disk usually mounted on the output side is referred to as the hub disk, and it is usually enclosed on both sides by side elements. In the case of dual-mass flywheels, this hub disk would be enclosed, for example, by a flywheel on one side and by a cover plate connected to it on the other side. The actual transmission of the torque between the output side and the input side takes place between the side elements on the input side and the hub disk on the output side. The two elements are connected elastically to each other by spring-type stored-energy elements. Upon rotation of the side elements, special projections on these elements exert force on the spring elements, which transmit the force in turn to certain areas of the hub disk located at the other end of the spring devices. Thus the side elements and the hub disk rotate around a common rotational axis. Fluctuations in the torque, which are transmitted from the input side drive to the cover plates, are filtered out to a greater or lesser extent by the spring-type stored-energy elements, so that the torque has a smoother curve at the output-side hub disk.
The torsional vibration system in a clutch mechanism, for example, or in a dual-mass flywheel can be described with respect to its critical resonance speed n
k
as follows:
n
k
=SQRT
((1
/J
1
+1
/J
2
)*
c*K
)*30/(&pgr;*
Z
)
where:
J
1
and J
2
are the inertias of the primary and secondary side;
c is the stiffness of the spring(s);
K is a correction factor with K=1 if c is given in Nm/rad or with K=180/&pgr;if c is given in Nm/degree; and
Z is the number of out-of-round events (such as ignitions in an internal combustion engine) per revolution of a drive shaft on the input side.
A disconnection can be achieved only above this rotational speed (starting at SQRT(
2
)×n
k
as a guideline value). In the case of the dual-mass flywheel, the two inertias are approximately the same. Thus the term in parentheses reaches a minimum. In the case of a clutch disk, J
1
can have a value of up to 100×J
2
. Thus the inertia J
2
represents an essential “lever” by which the natural frequency of a torsional damping system with a clutch disk can be lowered. The change in the critical speed obtained by shifting the moments of inertia of the term in parentheses, including the root, from the primary to the secondary side is shown in FIG.
7
. Point A characterizes here the typical ratio for a dual-mass flywheel, which can be, for example, about 60:40, whereas point B shows the ratio for a typical clutch disk. As can be seen, in the case of the dual-mass flywheel, changes will have hardly any effect because of the very wide minimum. In the case of a clutch disk, however, the resonance point of the system can be changed significantly.
A further improvement in the torque behavior can be obtained by connecting an auxiliary mass (usually by way of a damping element) to the input or to the output side of a torsion damper.
As a result, the mass moment of inertia (MMI) of the output side or of the input side is greatly increased, so that at least one natural frequency of the total system is lowered and the so-called supercritical speed range of the drive is significantly increased. It is especially favorable to increase the mass moment of inertia on the output side of a torsion damping mechanism, because the mass moment of inertia is very small here in comparison to the mass moment of inertia on the input side, which means that even a very small amount of additional mass brings about a very sharp increase, in relative terms, in the mass moment of inertia on the output side. The auxiliary mass is preferably connected by way of a damping element. A damping element is preferred which is designed for dry friction, although viscous fluid damping or some other type of damping principle such as magnetic field damping or piezoelectric element damping could also be imagined. The effective friction between the auxiliary mass and the output or the input side can thus be set to any desired value within a wide range.
When peaks which exceed the preadjusted frictional moment now occur in the torque from the input side, e.g., a drive such as an engine, or from the output side, such as a transmission, the auxiliary mass slips, as a result of which energy is dissipated. In this way, the torque peaks in a drive train are capped, and thus the rotational irregularities are reduced.
A torsion damping mechanism can be divided into an input side (primary side) and an output side (secondary side). The input side comprises all the elements of the torsion damping mechanism up as far as the spring-type stored-energy elements, on which an external drive force acts. The output side comprises all the elements which are located on the other force-transmitting side of the spring elements and which transmit the drive force further onward via a flywheel, for example, to a clutch mechanism. As a rule, the hub disk is one of the output elements, whereas the side elements belong to the input side. It is fundamentally possible, however, to reverse the arrangement of these elements, so that the hub disk belongs to the input side, a possibility which is also to be included within the scope of the invention.
An area of application in which torsion damping mechanisms are used includes dual-mass flywheels. These are flywheels which are connected to drives which run irregularly such as internal combustion engines to make them run more smoothly; they are usually installed upline of the clutch. Dual-mass flywheels usually consist of two coaxially aligned flywheels, which are connected to each other by a torsion damper. The input side and the output side of dual-mass flywheels are usually connected by a bearing, so that one side can rotate relative to the other side. The bearing is usually oriented radially and is connected to the two sides by means of projections, areas bent into the shape of a crank, or hub-like formations on the input side or output side.
In a clutch mechanism, the clutch disk is connected to the cover plates on each side of the torsion damper (or to the hub disk). In the case of conventional dual-mass flywheels, however, one of the flywheels takes the place of one of the cover plates. The cover plate located on the other side of the hub disk has a function similar to that of the second cover plate in a clutch mechanism, in that it closes off the entire mechanism, especially the torsion springs. In dual-mass flywheels, this cover plate can also have an additional function, namely, to serve as a sealing element for so-called “wet-running” dual-mass flywheels.
In dual-mass flywheel arrangements, the hub disk is connected by appropriate fastening elements such as bolts to the second flywheel.
In many designs, one of the two flywheels of the dual-mass flywheel serves simultaneously as the flywheel of a clutch mechanism, which is connected downline from the dual-mass flywheel.
An essential cost factor in torsion damping mechanisms with auxil

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