Abstract:
A method for controlling the power consumption of a starting element ( 1 ) in the form of a hydrodynamic clutch ( 2 ). The clutch comprises an impeller ( 4 ) and a turbine wheel ( 5 ), which together form at least one toroidal working chamber ( 6 ) that can be filled with an operating medium, and is located in a drive train ( 3 ) with at least one other drive motor that can be coupled to the hydrodynamic clutch. The method is characterized in that the power consumption can be freely adjusted as a function of the volumetric efficiency of the hydrodynamic clutch and the method has the following characteristics: the supply or evacuation of the operating medium to or from the working chamber is influenced by the generation and introduction of a static superposition pressure in the closed rotating circuit; the operating medium is supplied or evacuated to or from the working chamber by the application of a superposition or influencing pressure to the operating medium level in the operating medium reservoir ( 40 ).

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to a method for controlling the power consumption of a hydrodynamic clutch, in particular as starting element in a drive train by controlling the volumetric efficiency. 
   During the starting process, i.e. the run-up of the drive motor and simultaneous transmission of torque on the output unit in a drive train, in particular in vehicles but also in stationary units, the problem of energy consumption of the drive motor is increasingly the center of attention since during this process usually too little energy for self-acceleration of the drive motor is available. As starting elements in vehicles hydrodynamic clutches are used for this purpose among other things. They are well-known in a multiplicity of designs. Reference is made to the publication Voith:“Hydrodynamics in motive power engineering”, Vereinigte Fachverlage, Krauskopf Engineer Digest, Mainz 1987. The starting elements are usually integrated in a gear box unit. The gear box unit has for this a first hydrodynamic transmission part and a further second transmission part, which is usually preferably formed by a mechanical transmission part for application in vehicles. Since the power consumption of the hydrodynamic clutch is dependent on its design and not on a machine, which is at least indirectly connected to the hydrodynamic clutch on the output side, during the installation of such a component between a drive motor and a machine it is to be considered that for each load condition between the machine and the hydrodynamic clutch also a state of equilibrium must be ensured between the drive motor and the hydrodynamic component. Thereby the power released by the drive motor is in the rarest case completely available to the gear unit, in particular the hydrodynamic component, during the starting process. Power for auxiliary machines, like for example fans, generators, pumps and so on, which are positioned before the starting element respectively the gear inlet, must thereby be subtracted from the available drive power. For the use of a hydrodynamic component in form of a hydrodynamic clutch the following specified benefits of the hydrodynamic power transmission are thereby desirable for the starting process: wear-free as well as vibration reducing and thermally stable. In connection with drive motors for different application functions concrete demands are made regarding the transfer characteristic also during the starting process. In particular for the application in vehicles a certain behavior during the starting process, in particular a certain power consumption by the impeller of the hydrodynamic clutch, is desired in order to be able to drive the drive motor in an optimized operating range regarding a certain parameter. During the starting process at low speeds it is therefore required that a suitable surplus moment is present for the self-acceleration of the drive motor in order to realize a motor start-up that is relieved as much as possible. 
   SUMMARY OF THE INVENTION 
   It is therefore the task of the invention, to further develop a starting unit of the kind initially specified, in particular a method for controlling the power consumption, in such a manner that said starting units are suitable in particular for the application in drive trains of vehicles or other ranges of application, whereby besides the advantages of the hydrodynamic power transmission also a substantially relieved start-up of the drive motor should be ensured. The design of the starting unit should be characterized by a low expenditure for design, production and control and it should be economical. Furthermore the solution according to the invention, independently of the field of application at the hydrodynamic component, is to require only slight modifications. 
   According to the invention the power consumption as a function of its volumetric efficiency is freely adjustable with a method for controlling the power consumption of a starting element in form of a hydrodynamic clutch, comprising an impeller and a turbine wheel, which form with one another at least one toroidal working chamber that can be filled with operating medium, in a drive train with at least another drive motor that can be coupled with the hydrodynamic clutch. This possibility of free adjusting makes it possible, regarding different criteria, for example energy consumption and pollutant emission, to try to achieve optimized operating points in the characteristic diagram of the drive motor. 
   Thereby a change of the power to be received takes place by controlling the volumetric efficiency of the hydrodynamic clutch when a value is present, which characterizes the power desired to be received of the hydrodynamic clutch at least indirectly. The controlling of the volumetric efficiency takes thereby place preferably via creating and/or applying of an influence pressure on a resting medium, in particular on an operating medium level which arises in an operating medium reservoir within the scope of an operating medium utility system or on a control medium level. Thereby a portion of the operating medium in the working chamber is directed during the operation of the hydrodynamic clutch in a closed circuit between at least one outlet from the toroidal working chamber between impeller and turbine wheel and at least one inlet into the toroidal working chamber, whereby the inlet is connected with an operating medium reservoir which is pressure tight closed in relation to its surrounding. A manipulated variable is then created for the generation of an influence pressure on the medium resting in the operating medium reservoir and the servo unit is triggered. Filling or emptying takes place up to the point of reaching a pressure balance between the operating medium level in the operating medium reservoir and the rotary closed circuit. 
   A hydrodynamic clutch according to one form of the invention comprises at least two rotating circuit parts in the form of two impellers, which form with one another at least one toroidal working chamber, which can be filled with operating medium and in which a rotary working circuit arises during operation of the hydrodynamic clutch. An inlet and an outlet are assigned to the toroidal working chamber, which is connected with a closed circuit. Said working chamber comprises the working circuit and an external element, i.e. an element directed outside of the toroidal working chamber, which is connected with the working circuit. The external element of the circuit serves thereby among other things the purpose of directing the operating medium for the purpose of cooling. This closed circuit is designed according to the invention pressure tight. This means that the inlet, in particular the inlet area to the working chamber, and the outlet, in particular the outlet area are designed fluid tight in relation to the hydrodynamic clutch and that further the operating medium guide distance between the inlet and the outlet is completely sealed in the external element of the closed circuit, i.e. outside of the toroidal working chamber. 
   The solution according to the invention makes it possible that during operation of the hydrodynamic clutch operating medium is directed in the external element of the circuit with removal of operating medium from the working circuit into the external element of the closed circuit and, since the whole circuit is designed as a closed circuit, operating medium is again supplied to the inlet. Due to the pressure tight design a pressure in the closed system, created by the hydrodynamic clutch, is maintained during the operation of the hydrodynamic clutch, i.e. during rotation of an impeller and therefore by slaving at least another impeller by means of the working circuit. This circuit can be designated thereby by itself as cooling circuit, as heat can be dissipated by radiant heat over the line connections between the outlet and the inlet. Therefore already this design makes a cooling circuit possible. 
   If under a further aspect means for the generation of an influence pressure on the operating medium directed in the closed circuit are planned, the possibility consists to control additionally the volumetric efficiency of the hydrodynamic clutch. 
   Under a further aspect at least one junction location for the optional connection of means for the filling and/or emptying and/or means for the pressure default are arranged in the system in the closed circuit. The means for the pressure default are thereby preferably pressure tight connected to the closed circuit and serve the purpose of generating a static superposition pressure in the closed circuit. The means for the pressure default comprises preferably a pressure tight closed reservoir, which is pressure tight connected with the closed circuit. The pressure default takes place via applying a pressure on the reservoir level. Another possibility is the generation of a pressure through additional components, for example a suitable pump device. 
   The means for filling comprise an operating medium reservoir device and a means for the operating medium transport, for example pump devices. These serve also the purpose of loss compensation. 
   Under a further aspect of the invention the means for filling and emptying and the means for the pressure default are formed by a system for the purpose of the simplification of the overall system. Filling and emptying takes place preferably likewise by means of the reservoir, which is connected pressure tight to the closed system, and by applying pressure on the reservoir level or by pump devices. 
   An improvement of the invention contains the provision and/or the allocation of standing back pressure tubes to the diverting area, which is limited by a rotating housing component. Preferably a multiplicity of standing back pressure tubes is intended, which are arranged in a certain distance to each other in circumferential direction. The back pressure tubes function as a back pressure pump device when immersed into the diverting area and are connected with the line connections, which are connected with the diverting area. These convert the kinetic energy into pressure energy and create automatically a cooling circuit, which is required for ensuring the continuous operation of the hydrodynamic clutch. In a further design of the solution according to the invention means for the heat dissipation in the closed circuit are provided. These can be cooling devices or heat exchangers. 
   The hydrodynamic clutch designed as a starting element according to the invention is not limited to any specific application in drive trains. Application can take place in drive trains of stationary units or mobile devices, preferably in a vehicle. 
   BRIEF DESCRIPTION OF THE DRAWINGS 
   The solution according to the invention is in the following described using the following figures: 
     FIG. 1  illustrates a favorable design of a starting element in form of a turbo-clutch arranged according to the invention using a section of a drive train; 
     FIG. 2  illustrates the basic principle of the controlling of the volumetric efficiency using a diagrammatic representation of a hydrodynamic clutch and the operating medium utility system assigned to said clutch. 

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a favorable design of a starting element  1  in form of a hydrodynamic clutch  2  arranged according to one form of the invention, in particular a turbo-clutch using a section of a drive train  3 . The hydrodynamic clutch  2 , in particular a turbo-clutch, comprises at least one primary wheel functioning as impeller  4  and a secondary wheel functioning as turbine wheel  5 , which form with one another a toroidal working chamber  6 . The starting element  1  comprises further one drive unit  7 , that can be coupled at least indirectly with a drive motor (not shown), and one output unit  8  that can be coupled at least indirectly with the output unit at the drive system, i.e. indirectly via further transmission means or directly without inserting further transmission means. The output unit  8  can generally be coupled with a mechanical speed and/or torque transformer during the application in gear boxes. The drive unit  7  and the output unit  8  are formed for example in each case by a shaft or a hollow shaft or a flange. The hydrodynamic clutch  2  includes a housing  9 , which is connected secured against torsion with the impeller  4  and consists because of assembly reasons preferably of a multiplicity of individual housing components  25 . 1  - 25 . 3 . The housing  9  is therefore likewise connected secured against torsion with the drive unit  7 . In the represented case the housing  9  is therefore connected with a hub component  10 , which is designed flange-like at its end  11  facing the starting element, whereby the mounting, respectively the connection, secured against torsion between the hub component  10  and the housing  9  takes place in the area of a flange  12  of the hub component  10 . The drive of the hub component  10  takes place through a drive shaft  13 , which can be connected at least indirectly, i.e. either directly or over further power transmission components with a drive motor not represented here, and through a suitable shaft-hub connection  14  which in the represented case is designed as key joint  15  between hub component  10  and drive shaft  13 . Other design variations for the realization of a connection secured against torsion are likewise conceivable. The housing  9  encloses the turbine wheel  5  while forming a first gap  16  in axial direction. The first gap  16  is thereby limited by a housing inner wall  17  of a housing component  25 . 1 , by an outlet  18  from the impeller in the range of the parting plane  19  between impeller  4  and turbine wheel  5 , by the outer circumference  20  in the range of radially outer extension  21  of the turbine wheel  5 , and by a further housing component  25 . 2 , which is connected secured against torsion directly with the impeller  4  or which forms a structural unit with the impeller, in particular its inner surface  31 . Means  22  are intended for sealing the gap  16  between the housing  9  and the turbine wheel  5 . These means for sealing  22  comprise at least one non-contact sealing device  23 , which is designed preferably in form of a labyrinth seal. The housing  9  forms further a second gap  28  with the impeller  4  and a further housing component  25 . 3 , connected secured against torsion to the impeller, as well as a second housing  51  with rotates with relative speed in relation to the housing  9 , is preferably however stationary, which is mounted via an arrangement of bearings  26  on a driven shaft  27  which forms the output unit  8  of the starting element  1 . This second gap is essentially formed by the outer surface  29  of the impeller  4  in the radially outer portion  30 , by the housing component  25 . 2 , which carries the housing inner wall  31 , and by an inner surface  33  of the housing component  25 . 3  of the housing  9 , which at least partially encloses the impeller  4  in axial direction. The stationary housing  51  can be designed as one-piece or as multiple pieces. It can also rotate—depending on the connection to the output unit  8 —with relative speed in relation to the rotation of the housing  9 . A seal between the housing component  25 . 3  and a housing component  51 . 1  of the stationary housing  51 , into which line connections  41  for the realization of a closed operating medium circuit  42  are integrated, is created by means  34  for sealing the gap  28  between the housing  9  and the housing  51 , in particular the housing components  25 . 3  and  51 . 1 . These means comprise at least a non-contact gasket  35 , which is designed preferably in form of a labyrinth seal. The second gap  28  is connected at the housing component  25 . 2  with the first gap  16  via suitable transfer ports  36  in the housing wall  32 . Means  37  for the removal of operating medium appears in the second gap  28  during the operation of the hydrodynamic clutch via the operating medium guide in the toroidal working chamber  6 , are assigned to the second gap  28 , said means being designed for example in the form of back pressure pumps  38 . According to the desired amount of operating medium to be removed from the second gap  28  and the time period, which is available for the removal, preferably in dependence on the possible passage area, which is determined by the dimensioning of the back pressure pumps  38 , a multiplicity of back pressure pumps  38  is provided, which are preferably arranged in symmetrical distances in circumferential direction in the gap  28 , respectively submerged into the gap. The housing components  51 . 1  and  51 . 2  and the third housing component  25 . 3  form a back pressure pump housing  54 , the housing component  25 . 3  for itself alone the impeller shell  52 . The housing components  51 . 1  and  51 . 2  can also be designed as an integral unit, i.e. only one housing component is provided, which combines the housing components  51 . 1  and  51 . 2  as represented in FIG.  1 . The means for the removal  37 , in particular the back pressure pumps  38 , are connected with means  39  for directing of operating medium in a closed circuit  42 . The means  39  for directing the operating medium comprise therefore preferably line connections  41  in the form of operating medium channels  50 , which are integrated into the housing wall facing the impeller  4  respectively into the housing components  51 . 1  and  51 . 2  of the housing  51 . The rotating housing  25  and the housing  51 , which is either stationary or rotating with relative speed to the housing  25 , form the total housing  55  for the clutch  2 . The operating medium utility system  53  comprises an operating medium reservoir  40 , which is connected with the closed circuit  42  via a knot location  56 , for example by means of a line connection. The operating medium reservoir  40  is preferably arranged in the area below the height of the toroidal working chamber  6 , in particular within the outer radial dimensions of the individual impellers  4  or  5  in assembled position. In this case a safety device via a siphon or other aids can be omitted. 
   The operating medium reservoir  40  is thereby pressure tight connected with the inlet  44  into the toroidal working chamber  6  via the junction  56 . The means for sealing  34  of the gap  28 , in particular of the back pressure pump housing  54  and the impeller shell  52 , as well as the means  22  for sealing between turbine wheel  5  and the rotating housing  9  of the starting unit  1  are spatially arranged in circumferential direction above the meridian center and below the maximum profile diameter of the two impellers, i.e. the impeller  4  and the turbine wheel  5 . Furthermore means  43  are provided for sealing between impeller  4  and turbine wheel  5 , whereby these means are arranged in radial direction inside the internal diameter dE of the toroidal working chamber  6 . The closed circuit  42  is thus pressure tight in relation to its surrounding. The connection of the operating medium reservoir  40  to the closed circuit  42  takes place likewise pressure tight. 
   The housing of the starting unit  9 , the impeller  4 , the turbine wheel  5 , the closed circuit  42  as well as the pressure tight connection of the operating medium reservoir  40  with the closed circuit  42  form means  45  for the generation of a pressure balance between a closed rotating circuit  42  and a resting medium. The closed circuit  42  is provided between the outlet  18  from the toroidal working chamber  6  in the area of the parting plane  19  and the inlet  44  into the impeller  4 . The operating medium arrives from the flow circuit in the toroidal working chamber  6  via the outlets  18  in the area of the parting plane  19  of the impeller  4  and the turbine wheel  5  and via the connection channels into the second gap  28 , from where the operating medium is directed via the means for the removal  37 , in particular the back pressure pumps  38 , into the closed circuit  42 . 
   The inlet  44  is via the filling location  47  connected with the operating medium reservoir  40 . In a particularly favorable design the filling location  47  is furthermore designed as bladed channel  48 . This means that direction components  49 , which extend in the direction of the flow toward the toroidal working chamber  6 , are provided. The reduction of the operating medium stream via the outside impeller shell  52 , formed by the housing component  25 . 3 , preferably takes place via a multiplicity of stationary back pressure pumps  38 , which are arranged to each other in circumferential direction preferably symmetrically. The circuit created for cooling purposes is thereby designed as closed circuit  42 . 
   The working principle of the filling control by means of an outside pressure onto a resting medium is described in diagrammatic simplified representation in FIG.  2 . This figure illustrates in diagrammatic simplified representation a hydrodynamic clutch  2 , the closed circuit  42  assigned to the clutch, which is designed as a coolant circle, and the connection between the turbo-clutch  2  and the operating medium reservoir  40 . The inlet into the working chamber  6  is shown to be arranged at the turbine wheel  5 . The operating medium reservoir  40  is thereby for example designed as tank or vessel, whereby it can also be formed by the housing of the starting unit or of the gear box in which the starting element  1  is arranged. The operating medium reservoir  40  is thereby preferably arranged below the internal diameter d E  of the toroidal working chamber  6 . It is thereby crucial that the operating medium level is either below this dimension or it can be above, with the presence of suitable aids, for example in the form of siphons and/or valves. The closed coolant circuit  42  is designed between the toroidal working chamber  6  respectively the outlet  18  from the toroidal working chamber  6  and the filling location  47  of the toroidal working chamber  6 . Means for the heat dissipation of operating medium  57  are for example arranged in said circuit. These means  57  comprise in the simplest case for example a heat exchanger or a cooling device. Directing the operating medium from the working chamber  6  into the working chamber  6  in the closed circuit  42  serves thereby mainly the purpose of cooling the operating medium, in particular the generation of a continuous cooling operating medium flow. The operating medium utility system comprises a pressure tight designed operating medium reservoir  40 , for example in form of an operating medium sump in a reservoir, a tank or a housing, which can be connected via at least one connection channel with the closed circuit  42  in the area of the inlet  44 . The operating medium reservoir  40  is thereby preferably arranged in such a manner that the arising operating medium level is arranged underneath the toroidal working chamber  7 . An influence pressure P B  for the change of the volumetric efficiency FG is applied on the operating medium level, whereby said influence pressure during effect on the closed sump allows operating medium to enter the working circuit in the toroidal working chamber via connection channels, until the pressure within the area of the inlet  21  after the heat exchanger creates a pressure balance. Filling or emptying takes place until a pressure balance between the operating medium level in the operating medium reservoir and the rotary closed circuit arises. 
   Furthermore, as shown in  FIG. 1 , the profiles of the turbine wheel  5  and the impeller  4  are offset in radial direction against each other by a certain value in such a manner that the outside profile diameter of the turbine wheel  5  exhibits a larger dimension in radial direction than the outside profile diameter of the impeller  4  and the interior profile diameter of the turbine wheel  5  exhibits likewise a larger dimension than the internal diameter of the impeller profile. 
   A change of the ideal torus-symmetrical form can take place moreover via a profile offset. 
   The back pressure pumps  38  supply with emptied turbo-clutch  2 , when all circuit parts are free of operating medium, a flow rate and an oil pressure for cooling or for actuation for other consumers, like for example a wet-running mechanical clutch. 
   Further favorable designs include means for the improvement of the filling of the working chamber, i.e. the pump characteristic, by providing elements built into the filling area  48  connected with the filling location  47 . These elements built in can be designed as filling blades  49 , perforated plate packages or similarly designed areas. Furthermore it is conceivable to design the filling of the impeller  4  through several blade cascades in arbitrary parts of the torus or through the blade itself, for example a stamped channel to the torus center. 
   Further improvements can have the blades of impeller  4  and turbine wheel  5  designed with different blade angles. Additionally or as an individual solution the blades of impeller  4  and turbine wheel  5  can be sharpened differently, which entails into different dimensions across the extension in circumferential direction of the individual blade. Another possibility consists of changing the entry angles and outlet angles between impeller and turbine wheel or to provide a different number of blades in the mounting of blades of impeller  4  and turbine wheel  5 .
       1  Starting element     2  Turbo-clutch     3  rive train     4  Impeller     5  Turbine wheel     6  Toroidal working chamber     7  Drive unit     8  Output unit     9  Housing     10  Hub component     11  End range facing the starting element     12  Flange     13  Drive shaft     14  Shaft-hub connection     15  Key joint     16  Gap     17  Housing inner wall     18  Outlet     19  Parting plane     20  Outer circumference     21  Radially outer extension     22  Means for sealing     23  non-contact sealing device     25 . 1 ,  25 . 2 ,     25 . 3  Housing component     26  Arrangement of bearings     27  Driven shaft     28  Gap     29  Outer surface     30  radially outer range     31  Inner surface     32  Housing wall     33  Inner surface     34  Means for sealing the gap  28       35  Non-contact gasket     36  Transfer port     37  Means for the removal of operating medium from the working chamber     38  Back pressure pump     39  Means for directing the operating medium     40  Operating medium reservoir     41  Line connections     42  Closed circuit     43  Means for sealing between impeller and turbine wheel     44  Inlet     45  Means for the generation of a pressure balance between a closed rotating circuit and a round medium     47  Filling location     48  Filling area     49  Bladed direction components     50  Operating medium channels     51  Resting housing component     52  Impeller shell     53  Operating medium utility system     54  Back pressure pump housing     55  Total housing     56  Knot location     57  Means for heat dissipation   d E  Inner diameter of the toroidal working chamber