Drive train with rigidity dependent on rotational speed

Details Drive train with rigidity dependent on rotational speed Drive train with rigidity dependent on rotational speed

2000-06-12

2002-08-20

Marmor, Charles A (Department: 3681)

Planetary gear transmission systems or components

Fluid drive or control of planetary gearing

Impeller-turbine type fluid circuit and mechanical path in...

C475S255000, C475S347000, C074S574300, C192S003280

Reexamination Certificate

active

06435998

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a drive train of a motor vehicle with an internal combustion engine, a transmission and a flywheel mass arrangement assigned to a torque transmission path between the internal combustion engine and the transmission, the flywheel mass arrangement has a drive-side flywheel mass assigned to a driven shaft of the internal combustion engine, a transmission-side flywheel mass assigned to an input shaft of the transmission, and a gear arrangement which is connected between the two flywheel masses which are rotatable at least to a restricted extent relative to one another or between part flywheel masses thereof which are rotatable at least to a restricted extent relative to one another, the gear arrangement is effective in at least one operating state for transmitting at least part of a torque flow between the internal combustion engine and the transmission. The gear arrangement includes at least one planet wheel which is coupled via a meshed engagement with a sun wheel or a ring wheel and is rotatable at least to a restricted extent about a planet wheel axis. The planet wheel has at least one rotational additional mass, the center of gravity of which is offset relative to an axis of rotation assigned to said additional mass, the gear arrangement converting a relative rotation of the two flywheel masses or part flywheel masses into a rotation of the additional mass about the axis of rotation assigned to the latter, with the center of gravity being displaced radially in relation to a flywheel mass axis of rotation.
2. Description of the Related Art
To improve the dynamic behavior of the drive train of motor vehicles, torsional vibration dampers are arranged in the torque transmission path between the internal combustion engine and the transmission and recently are often designed as so-called two-mass flywheels. In the latter case, dividing the flywheel mass into two flywheel masses ensures that resonant frequencies of the gear and of the drive train are well below the frequencies of vibrations emanating from the internal combustion engine (engine). This avoids resonances which may lead to noises, such as gear rattling and body drumming.
In the design of the torsional vibration damper, if appropriate the two-mass flywheel, it is often a conflict of aims as regards the resulting rigidity of the torque transmission path. Thus, a low torsional rigidity, that is to say a low value of the c-value usually described in terms of Nm/degrees would be advantageous for low rotational speeds so that the engine could be started with as little noise as possible. By contrast, a higher torsional rigidity should be ensured at higher rotational speeds so that the maximum torque of the internal combustion engine may be covered.
Conventional torsional vibration dampers usually operate with the same c-value over the entire rotational speed range. As a result, these conventional torsional vibration dampers are too rigid under some circumstances such as at low rotational speeds where the internal combustion engine can still exert a little torque.
A two-mass flywheel is disclosed in German reference DE 42 00 174 A1 in which a primary-side flywheel mass and a secondary-side flywheel mass are coupled via toggle lever arrangement. A mass accumulation which generates between the flywheel masses a centrifugally induced return force which increases with a rotational speed of the two-mass flywheel is provided proximate a pivot bearing between a primary-side lever and a secondary-side lever. The coupling of the flywheel masses via the toggle levers leads to an inertia matrix which defines the dynamic properties of the two-mass flywheel and has matrix elements which are dependent on a relative rotary angle of the flywheel masses. This arrangement also leads to a rigidity which is undefined at zero rotational speed from which nndesirable effects may consequently arise such as, for example, disturbing noises when the engine is started.
Another two-mass flywheel is disclosed in German reference DE 197 26 477 A1 in which a gear arrangement and a torsion damper spring arrangement each have a torque-transmitting effect between a primary flywheel and a secondary flywheel rotatable to a restricted extent relative to the latter. The gear arrangement comprises a plurality of planet wheels in a meshed engagement with a ring wheel fixed in terms of rotation relative to the secondary flywheel mass. Each of the planet wheels are assigned at least one additional mass and arranged so that the center of gravity of the at least one additional mass is displaceable radially in relation to an axis of rotation of the two-mass flywheel as a function of a relative rotary position of the ring wheel and of the planet wheel carrier to change a moment of inertia of the two-mass flywheel. This arrangement of a two-mass flywheel takes effect as a selfsteadying system since there is no definite resonant point.
The reference DE 197 26 477 A1 does not mention centrifugally induced return forces acting on the two flywheel masses. However, an analysis of the system disclosed in
FIG. 1
of DE 197 26 477 A1 reveals that a centrifugally induced return force increasing with a rotational speed of the two-mass flywheel occurs at all events and takes effect between the primary flywheel mass having the planet wheel carrier and the secondary flywheel mass connected fixedly in terms of rotation to the ring wheel. Whether this centrifugally dependent return force is at all relevant, as compared with a spring arrangement acting between the two flywheel masses, cannot be inferred from the preliminary publication because of a lack of information on the spring forces in the masses. As far as information regarding the different embodiments disclosed in DE 197 26 477 A1 together with the information on the relative angles of rotation between the two flywheels applies to the arrangement of the additional masses to the planet wheels, the arrangement is such that the return force acts on both sides of an unstable intermediate relative rotary angle position of equilibrium, which lies between two relative rotary angle boundary positions delimiting a relative rotary angle range of the flywheel masses, in the direction of the respective nearer relative rotary angle boundary position. It follows from this that the spring arrangement acting between the flywheel masses is required and, moreover, must have a sufficiently high spring force, since otherwise, at least at high rotational speeds, there is the risk that the two flywheel masses may assume a relative rotary position corresponding to the relative rotary angle boundary positions and torsional vibrations may correspondingly be damped at most only incompletely.
A torque converter with a planetary gear which serves for coupling a turbine wheel and a piston of a bridging clutch is known from European Patent No. 0 306 169 B1.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a drive train in which the torque transmission path has lower effective rigidity in a range of lower rotational speeds than in a range of higher rotational speeds so that an internal combustion engine can be started with as little noise as possible and a maximum drive torque capable of being exerted by the internal combustion engine may be conducted by the drive train.
To achieve this object, a drive train of a motor vehicle with an internal combustion engine, a transmission and a flywheel mass arrangement assigned to a torque transmission path between the internal combustion engine and the transmission is provided in which the flywheel mass arrangement has a drive-side flywheel mass assigned to a driven shaft of the internal combustion engine, a transmission-side flywheel mass assigned to an input shaft of the transmission, and a gear arrangement which is connected between the two flywheel masses which are rotatable at least to a restricted extent relative to one another or between part flywheel masses thereof which are rotatable at least to a re

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