1. Field of the Invention
The invention pertains to a torsional vibration damper in the bridging clutch of a hydrodynamic clutch arrangement having an axis of rotation, a clutch housing, a turbine wheel, and a takeoff-side component, wherein the torsional vibration damper includes a drive-side connecting device comprising a drive-side transmission element which can be connected to the clutch housing; a takeoff-side connecting device comprising a take-off side transmission element which can be connected to the takeoff-side component; an intermediate transmission element between the connecting devices; first energy storage devices connecting the intermediate transmission element to the drive-side connecting device; and second energy storage devices connecting the intermediate transmission element to the takeoff-side connecting device.
2. Description of the Related Art
A torsional vibration damper of this type is known from, for example, U.S. Pat. No. 5,080,215, FIG. 3. The hydrodynamic clutch arrangement, realized as a torque converter, is designed with a bridging clutch, the piston of which is provided with a friction surface on the side facing the clutch housing. This friction surface of the piston can be brought into frictional contact with an opposing friction surface. The bridging clutch establishes a working connection between the clutch housing and the torsional vibration damper, in that a radially outer hub disk of the damper engages with the piston in such a way that it cannot rotate relative to the piston but can move in the axial direction. The radially outer hub disk acts as a drive-side transmission element of the torsional vibration damper and works together with first energy-storage devices and with cover plates, which serve as an intermediate transmission element of the torsional vibration damper, to form a drive-side connecting device. The cover plates, which are a certain axial distance apart, cooperate in turn with second energy-storage devices and with a radially inner hub disk, which is part of a takeoff-side transmission element, to form a takeoff-side connecting device. Like the radially outer hub disk, the radially inner hub disk is located here axially between the cover plates. Like the intermediate transmission element and the takeoff-side transmission element, the drive-side transmission element also has driver elements for the energy-storage devices.
The radially inner area of the hub disk of the takeoff-side transmission element is connected by a set of teeth to a retaining bracket so that it cannot rotate but can move in the axial direction, the bracket also being a part of the takeoff-side transmission element. This bracket is attached to a turbine wheel hub, which also permanently holds the base of the turbine wheel. The turbine wheel hub can be connected nonrotatably by a set of teeth to a takeoff-side component of the hydrodynamic clutch arrangement such as a gearbox input shaft.
When considered as a freely vibrating system with a hydrodynamic clutch arrangement, the power train of a motor vehicle can be reduced to roughly to six masses. The drive unit with a pump wheel is the first mass; the turbine wheel is the second mass; the gearbox input shaft is the third mass; the universal shaft and the differential represent the fourth mass; the wheels are the fifth mass; and the overall vehicle itself can be assumed to represent the sixth mass. In the case of a freely vibrating system with n masses, or 6 masses in the present case, it is known than n−1 resonant frequencies, thus five resonant frequencies in the present case, can be present. The first of these pertains to the rotation of the overall vibrating system and is therefore irrelevant with respect to the damping of vibrations. The rotational speeds at which the resonant frequencies are excited depend on the number of cylinders of the drive unit, which is in the form of an internal combustion engine. FIG. 3 of the present application shows a logarithmic amplitude-versus-frequency plot of the vibrations at the turbine wheel of a hydrodynamic clutch arrangement.
To help minimize fuel consumption, there is a trend toward closing the bridging clutch at very low rpm's in order to minimize the losses in the hydrodynamic circuit caused by slippage. For the bridging clutch, this means that it is closed at a frequency which, although it may be above the first and second resonant frequencies EF1 and EF2, is still below the third and fourth resonant frequencies EF3 and EF4. Whereas the first two resonant frequencies EF1 and EF2 in the hydrodynamic circuit of the hydrodynamic clutch arrangement can be damped, the power train can be excited to cause undesirable noise as it passes through the third and fourth resonant frequencies EF3 and EF4. The third resonant frequency EF3 in particular can still have very high amplitudes.
To return to U.S. Pat. No. 5,080,215, the torsional vibration damper according to FIG. 3 has connecting devices arranged in series; the device on the drive side is provided on a component of the bridging clutch, the component in the present case being the piston, and the device on the takeoff side is supported on a takeoff-side component of the hydrodynamic clutch arrangement such as a gearbox input shaft. Despite the presence of two connecting devices, the torsional vibration damper is comparable in operative terms to a torsional vibration damper which has only a single connecting device between its drive part and its takeoff part, whereas, at the same time, because the takeoff-side transmission element of this torsional vibration damper is connected nonrotatably to the turbine wheel, it acts as a “standard damper” as it is frequently called in professional circles.
A standard damper offers the possibility of damping the amplitudes of the third and fourth resonant frequencies EF3 and EF4 equally, both of which are perceived to be unpleasant, but it is unable to reduce the third resonant frequency EF3 to such an extent that it no longer generates an unpleasant effect.
DE 195 14 411 A1 describes a bridging clutch in which the drive-side transmission element of a torsional vibration damper is in working connection with a turbine wheel hub of a hydrodynamic clutch arrangement, whereas the takeoff-side transmission element of the damper is in working connection with a takeoff-side component of the clutch arrangement, usually configured as the gearbox input shaft. These types of torsional vibration dampers, in which the takeoff-side transmission element and the turbine wheel have the freedom to rotate relative to each other, are called “turbine dampers” in the trade and have the following property:
As a result of the direct connection of the takeoff-side transmission element of the torsional vibration damper to the gearbox input shaft, the connecting device, which is also provided with energy-storage devices and the drive-side transmission element, acts as a component connected in series with the torsionally elastic gearbox input shaft. Because the connecting device is not nearly as stiff as the gearbox input shaft, however, the overall stiffness is such that the gearbox input shaft must be considered very “soft”. This results in a very effective isolation of vibrations.
With respect to the resonant frequencies in the power train, the greater “softness” of the gearbox input shaft has the result that the third and fourth resonant frequencies EF3 and EF4 have greater amplitudes than those observed with a standard damper, but also that the third resonant frequency EF3 appears at much lower rpm's, namely, at rpm's on the order of the second resonant frequency EF2. The third resonant frequency EF3 therefore has virtually no effect in practice. No influence, however, can be exerted on the fourth resonant frequency EF4, which means that noise can occur when the rpm range associated with it is reached.