Hydrodynamic clutch

Details Hydrodynamic clutch Hydrodynamic clutch

2001-06-26

2003-01-07

Lorence, Richard M. (Department: 3681)

192 clutches and power-stop control

Vortex-flow drive and clutch

Including drive-lockup clutch

C192S1050BA

Reexamination Certificate

active

06502678

ABSTRACT:

The invention relates to a hydrodynamic coupling, in particular a hydraulic transmitter, specifically having the features from the preamble of claim
1
.
A wide range of designs of hydrodynamic couplings with clutches for synchronization, in particular in the form of friction clutches actuated by centrifugal forces, are known. As a representative sample in this context, reference is made to the following documents:
1. DE 31 19 171
2. Shinko Engineering Co., LTD “Shinko Fluid Couplings”, EFK.012 1 100782T
3. “Hydromechanical Couplings”
4. DE 17 75 184
Each of these embodiments comprises a hydrodynamic coupling, in particular a hydraulic transmitter, which operates on the basis of the Föttinger principle and in which, by means of a pump impeller, mechanical energy in the form of rotational energy of the drive shaft, is converted into kinetic energy, i.e. flow energy of the operating medium, this flow energy, on the output side, being converted back into rotational energy by a further bucket wheel. The operating medium used is primarily oil, and in some special cases also water.
Hydrodynamic couplings of this type substantially comprise at least three parts, two bucket wheels, one outer wheel and one inner wheel which is enclosed by a coupling shell which is coupled to the outer wheel. The function of the bucket wheels as pump impeller and turbine wheel is generally dependent on the direction of power transmission, taking the direction of rotation into account. If the pump impeller is driven, i.e. the outer wheel or the inner wheel, a circuit of the operating medium is formed in the radial and axial planes in the toroidal working space between outer wheel and inner wheel. In the process, a circumferential force, which transmits the torque, and additionally an axial force are active. The circuit is maintained for as long as there is a difference in torque in the form of what is known as the slip S between the drive side and the output side. If both bucket wheels are running synchronously, the circuit breaks up and no further torque is transmitted. In this case, a hydrodynamic coupling, in nominal operation, is generally designed for 2 to 3 percent slip, i.e. the efficiency is then approximately 97 to 98 percent. To improve the efficiency, it is necessary to connect a friction clutch in parallel. In order, however, to maintain the start-up properties of the hydrodynamic coupling which are particularly advantageous on account of the hydrodynamic power transmission, in particular the property of gentle acceleration of extremely large masses with virtually zero wear, this friction clutch may only be shifted with a low slip. The design of the parallel circuit of the friction clutch and its arrangement or association with respect to the hydrodynamic coupling is known, in various designs, from the above-mentioned documents. In the design described in document DE 31 19 171, the friction clutch comprises two clutch halves, which can be actuated by a fluid pressure which is dependent on centrifugal force. In this case, a shift element which actuates the clutch, preferably a piston which can be displaced in the axial direction and a pressure chamber, which can be filled with liquid and in which, during rotation, a fluid pressure which is dependent on centrifugal force and acts to close the clutch, is built up, rotates with one half of the clutch. For this purpose, a reservoir which is separate from the shift element is provided in said clutch half, this reservoir being connected to the pressure chamber via at least one fluid line. A control element controls the degree of filling of the pressure chamber with liquid as a function of the rotational speed of the said clutch half. In this case, with the reservoir arranged closer to the axis of rotation of the clutch than the pressure chamber, the end faces which delimit the pressure space are matched to one another in such a manner that the volume of the pressure chamber adopts a value of virtually zero when the clutch is open. When a clutch of this type is coupled to a hydrodynamic coupling, the secondary shaft, that is to say the shaft which is connected to the turbine wheel, is connected to one half of the friction clutch. When the clutch is closed, the pump impeller and turbine wheel of the hydrodynamic coupling rotate synchronously. In this embodiment, the synchronizer clutch is arranged outside the hydrodynamic coupling and has to be coupled to the latter in a corresponding way, which means that the structural size taken up is considerably increased in the axial direction and, in addition, the structural outlay is considerably increased.
In the embodiments described in the documents listed under 2 to 4, the synchronizer clutch, which is designed as a friction clutch, is integrated in the hydrodynamic coupling or forms a structural unit therewith. In the document mentioned under 2, the outer wheel is assigned the function of the pump impeller and the inner wheel is assigned the function of the turbine wheel. The coupling shell, which encloses the turbine wheel is designed to be extended in the axial direction and is used as a drum, in which centrifugal weights rotate, which are driven by driver elements on the inner wheel. In addition to the increased need for space, a considerable drawback is the particular design of the inner wheel, which has to be equipped with driver elements for the centrifugal weights, and this has to be taken into account even during production of the inner wheel, in design and in selecting the material used. The driver elements are in this case, according to the proposed solution, screwed to the inner wheel, which also considerably increases outlay on assembly. Furthermore, it is impossible to rule out operating disruption, since during operation loosening of the screw connections can cause considerable damage.
In the coupling designs which are described in the documents listed under 3 and 4, the inner wheel is assigned the function of the pump impeller and the outer wheel is assigned the function of the turbine wheel. In this case too, the synchronizer clutch is integrated in an elongated region of one of the elements, in particular of the inner wheel, by this elongated region being designed as a drum in which centrifugal weights rotate, but these weights are driven by driver elements on the outer wheel, in particular the turbine wheel. This solution also takes up considerable amounts of space in the axial direction in its installed position. The extended region has to be taken into account when producing the pump impeller, either requiring a single-part design when producing the casting or having to be connected to the pump impeller via an additional material-to-material bond. In the other case, corresponding connecting elements are to be provided, with the result that an increased outlay on assembly is to be noted in addition to the outlay on manufacturing technology.
The hydrodynamic couplings with synchronizer clutches—either associated or integrated—which are known in the prior art all have the drawback that the structural length in the axial direction is increased considerably compared to a conventional hydrodynamic coupling without synchronization. Further drawbacks are the increased structural outlay, manufacturing outlay and installation outlay, with considerably increased costs as a result. Furthermore, on account of the connections which have to be produced between the individual elements when integrating the synchronizer clutch in the hydrodynamic coupling, it is impossible to rule out the possibility of malfunctioning or disruption as arise in the event of the driver elements and therefore also the centrifugal bodies coming loose, which may lead to substantial, and in some cases even irreparable, damage to the individual elements.
The invention is therefore based on the object of further developing a hydrodynamic coupling of the type described in the introduction with a synchronizer clutch in such a manner that the above-mentioned drawbacks are avoided. In particular, the aim is to find a solution whic

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