Torsion damping mechanism with auxiliary mass

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

2001-10-05

2004-04-13

Rodríguez, Saúl J. (Department: 3681)

192 clutches and power-stop control

Clutches

Axially engaging

C192S03000R, C192S212000

Reexamination Certificate

active

06719112

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 of the one or more disks, and an output area, also usually disk-like in shape, which, in the case of clutch mechanisms, is connected to a hub, which can drive an output drive axle. The disk usually located on the output side is called the hub disk, and it is usually surrounded on both sides by cover plates, which are tightly connected to the torque-transmitting disk on the input side. Torsion damping mechanisms with one cover plate also exist. Dual-mass flywheels do not have cover plates, but they do have comparably functioning elements, namely, a primary flywheel and a cover plate, which is connected to the flywheel. The actual transmission of the torque between the output side and the input side takes place between the cover plate or plates or the flywheel/cover plate combination 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 cover plates or of the flywheel/cover plate combination, special projections on them exert force on the spring elements, which transmit this force in turn to certain areas of the hub disk located at the other end of the spring elements. Thus the cover plates or the flywheel/cover plate combination and the hub disk all 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 curve of the torque at the output-side hub disk becomes more uniform.
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/are the spring stiffness(es);
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.
12
. 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 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.
Especially in the case of clutch mechanisms, torsion damper disks usually have the smallest possible mass moment of inertia, because this must also be synchronized by the synchronizing device in the transmission when the clutch is released and when the gears are shifted. If, under such conditions, the mass of the input side or of the output side of a torsion damper disk is increased even more by adding extra mass, the synchronizing device in the transmission is negatively affected. For this reason, a disconnect device is positioned on the auxiliary mass to disconnect it from the torsion damper disk when the clutch is disengaged, so that the auxiliary mass does not have to be synchronized.
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, i.e., all the 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 devices, i.e., the elements which transmit the drive force further onward, including, for example, an output hub which drives an output drive shaft. As a rule, the hub disk is one of the output elements, whereas the cover plates 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.
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, these components are replaced by one of the flywheels and a cover plate, all of which therefore are to be referred to as “side elements” in conjunction with the present invention. The side element located on the other side of the hub disk, i.e., the cover element, 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 spring-type stored energy elements. In dual-mass flywheels, this second side plate can also have an additional function, namely, to serve as a sealing element in so-called “wet-running” dual-mass flywheels.
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 dua

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