Abstract:
A torque transmission device includes a torque converter, a pump impeller, a turbine wheel and optionally a stator. The device also includes a converter bypass coupling having a flange which is connected to the housing or the pump impeller in a force-locking manner. The flange is arranged between the pump impeller and the turbine wheel and can be connected to the turbine wheel in a frictionally engaged manner by means of a first coupling.

Description:
BACKGROUND 
   The present invention is directed to a torque transmission device, in particular for a motor vehicle, having a fluid coupling, such as a Föstinger coupling, or a torque converter, having at least one impeller that is connectable in a torsion ally fixed manner to a drive shaft of a drive unit, at least one turbine that is connectable in a torsion ally fixed manner to the input shaft of a drive train to be driven, as well as, optionally, at least one stator mounted between the impeller and turbine, at least one housing that accommodates the impeller and the turbine, as well as a converter lockup clutch, which is able to lock together the impeller and turbine in a torsion ally fixed manner. 
   SUMMARY OF THE INVENTION 
   Torque transmission devices of this kind are known in particular for fixed-ratio automatic transmissions. An object of the present invention is to improve the damping action of devices of this kind, the intention being for the rotational inertia and weight to correspond to those of related-art torque transmission devices, and for the dimensions, in particular the axial length, not to be increased in comparison to related-art torque transmission devices. 
   The present invention provides a torque transmission device in which the converter lockup clutch includes a flange that is connected by force-locking to the housing or the impeller, that is mounted between the impeller and the turbine, and that is connectable in a frictionally engaged manner by a coupling to the turbine. A connection is understood here to be both a direct connection as well as a connection that is produced, for example, via other, in particular, resilient elements. In this context, the other elements may be rigid or flexible. The flange may preferably be designed to be continuous, however a discontinuous flange is also conceivable. The flange is positioned in the axial direction between the turbine and the impeller. The possibility of having a frictionally engaged connection between the flange and the turbine means that, in a first operating position, both are substantially locked together in a torsion ally fixed manner, up to a limiting torque; in a second position, both are able to rotate freely relative to each other. 
   Another embodiment of the torque transmission device provides for the flange to be mounted on a tensional vibration damper that is coupled to the housing. The tensional vibration damper allows the flange to move against a spring force relative to the housing. 
   One preferred specific embodiment of the torque transmission device provides for it to also include a third switchable coupling, which may be used to uncouple the impeller from the input shaft, given a disengaged third coupling, the impeller being able to rotate relative to the input shaft. The third switchable coupling is preferably disposed between the impeller and the housing. 
   Another embodiment of the torque transmission device provides for it to include a second switchable coupling which enables the impeller to be locked together with the flange in a torsion ally fixed manner. In this manner, the impeller may be connected to the housing against the spring action of the damping device. 
   With the aid of the third coupling, it is possible to completely disconnect the impeller from the input shaft and, in this way, achieve a type of freewheeling state. In the standstill state, in particular, it is undesirable for a drag torque to be transmitted to the transmission, since this results in an avoidable thermal loading of the torque transmission device and, in comparison to a free idling of the engine, leads to an increased fuel consumption. With the aid of the second and third coupling, the impeller may be optionally connected to the input shaft in a torsion ally fixed manner or be connected to the input shaft via the vibration damper in a manner that permits rotation against a spring force. 
   Another embodiment of the torque transmission device provides for the flange to be able to be optionally coupled to the impeller and/or the turbine in a torsion ally fixed manner. With the aid of the first, second and third coupling described above, various operating states are able to be implemented in this manner. When all of the couplings are disengaged, consequently the flange is neither coupled in a frictionally engaged manner to the impeller nor to the turbine, and, at the same time, the third coupling is disengaged, then the torque transmission device is in a freewheeling state. For that reason, except for drag torques between the housing and the other devices, there is virtually no transmission of torque. At the least, any torque transmission is substantially less than in torque converter operation. In the case of an engaged third coupling, a torque converter operation takes place. If the first and second coupling are engaged, the third coupling, on the other hand, disengaged, then a lock-up operation follows, thus the turbine and impeller are locked together in a torsion ally fixed manner, both being driven via the vibration damper. The housing, on the one hand, and the turbine/impeller combination, on the other hand, form systems which are able to rotate relative to other, against the spring force of the vibration damper, the vibration behavior of the overall system being determined by the rotational inertias of the two mentioned subsystems, as well as by the damping and spring actions of the vibration damper, in particular. 
   The vibration damper is preferably accommodated within the housing. 
   One preferred specific embodiment of the torque transmission device according to the present invention provides for the impeller and/or the turbine to be axially displaceable within the housing. The axial displace ability of the turbine renders possible the first coupling; the axial displace ability of the impeller renders possible the second and third coupling. 
   Preferably, the first and/or second and/or third coupling are friction clutches. In addition, the friction clutches each include friction linings. 
   The first and/or second and/or third coupling may preferably be disengaged and engaged by axial displacement of the impeller and/or of the turbine. 
   It is preferably provided for the axial displacement of the turbine to take place hydraulically. It may also be provided for the axial displacement of the impeller to take place hydraulically. To that end, the torque transmission device includes a first pressure channel and a second pressure channel, which enable pressure to be applied axially to the turbine and the impeller. In this context, the turbine and impeller are mounted in a way that permits a fluid to stream through the entire torque transmission device; in other words, the first pressure channel is pressurized, for example, with the result that the entire torque transmission device is traversed by flow, hydraulic fluid flowing in through the first pressure channel and flowing out through the second pressure channel. 
   It is preferably provided for the first, second and third coupling to be disengaged when the first and second pressure channel are at approximately the same pressure. This may mean that the pressure prevailing in both pressure channels is approximately equal to zero. However, the pressure may also be at a different level. Because all of the couplings are disengaged, the torque transmission device is in a freewheeling state. 
   It is preferably provided for the third coupling to be engaged and the first and second coupling to be disengaged when the pressure prevailing in the first pressure channel is higher than the pressure prevailing in the second pressure channel. 
   It is preferably provided for the third coupling to be disengaged and the first and second coupling to be engaged when the pressure prevailing in the second pressure channel is higher than the pressure prevailing in the first pressure channel. The measures described above render possible three switching states of the couplings within the torque transmission device. In this manner, a freewheeling state, a torque converter operation, as well as a lock-up of the torque converter operation may be achieved. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     An exemplary embodiment is described in the following with reference to the enclosed drawing, in which: 
     The figure shows a torque transmission device according to the present invention in a sectional view. 
   

   DETAILED DESCRIPTION  
   A torque transmission device  1  includes a drive shaft  2 , which is connected to a crankshaft (not shown) of a combustion engine in a motor vehicle, as well as an input shaft  3 , which is connected to the automatic gearshift unit (likewise not shown). In addition, torque transmission device  1  includes a housing  4  made up of a first housing part  5 , as well as a second housing part  6 . First housing part  5 , as well as second housing part  6  are imperviously welded together at their periphery, for example. Torque transmission device  1  is rotatable mounted on a shaft end  7  of the transmission (not shown). With the aid of a sealing nose  8 , as well as sealing means (not shown), torque transmission device  1  is supported in a rotatable, but oil-tight manner on the transmission housing (not shown). 
   A turbine  9 , as well as an impeller  10  are mounted inside housing  4 . By way of a hub flange  11 , turbine  9  is connected in a torsion ally fixed, but axially displaceable manner to drive shaft  3 . Impeller  10  is mounted so as to be axially displaceable, as well as rotatable on a bearing projection  12  of housing  4 . Between impeller  10  and turbine  9 , a generally known stator  13  is supported by a freewheel  14  on transmission shaft end  7  in such a way that it is torsion ally fixed in one direction and rotatable in the other direction. Stator  13  is likewise displaceable in the axial direction. A first stop ring  15  provides for an axial bracing up of turbine  9  against housing  4 . Correspondingly, a second stop ring  16  provides for an axial bracing of stator  13  against turbine  9 . 
   Torque transmission device  1  has a first pressure channel  17 , as well as a second pressure channel  18 . Hydraulic oil may then be directed through the system via the pressure channels. 
   A tensional vibration damper  21  is positioned inside the periphery of first housing part  5 . It is preferably formed from bow springs nested in one another, two of the bow springs distributed over the circumference and extending approximately over half of the circumference preferably forming the energy storage that is effective in the circumferential direction. In this context, the bow springs are acted upon at one peripheral end by active loading devices (not shown in greater detail), which are joined to first housing part  5  or are formed from it, and, at the other end, by an axially extended piece of a flange  19 . In other words, flange  19  is rotatable against the force of the bow springs relative to first housing part  5 . Flange  19  is designed to be continuous inside of housing  4  and is provided with friction linings  20  on both sides. 
   Turbine  9  has a friction surface  22 , which forms a continuous, axial annular surface. Correspondingly, impeller  10  has a second friction surface  23 , first friction surface  22  and second friction surface  23  together being able to grip around flange  19 . The radially running surface of flange  19 , as well as first friction surface  22  and second friction surface  23  are substantially aligned in parallel with one another. In the present exemplary embodiment, first friction surface  22  and second friction surface  23  are braced by a first supporting flank  24  and a second supporting flank  25  against turbine  9  and impeller  10 , respectively, so that both are only slightly deformed in the axial direction in response to an axially applied load. 
   Second supporting flank  25  is provided on the side facing second housing part  6  with a third friction lining  26 . Together with flange  19  and associated friction lining  20 , first friction surface  22  forms a first coupling  27 ; correspondingly, together with flange  19  and associated friction lining  20 , second friction surface  23  forms a second coupling  28 ; together with second housing part  6 , third friction lining  26  forms a third coupling  29 . 
   The various modes of operation of the torque transmission device according to the present invention are described in the following. In this context, the distinction is made among a freewheeling operation, a torque converter operation, as well as a lock-up operation. 
   The various modes of operation may be carried out by a pressurization of first pressure channel  17  and of second pressure channel  18 . If first pressure channel  17  and second pressure channel  18  are pressurized with the same pressure or are kept in an unpressurized state, then first, second, and third coupling  27 ,  28 ,  29  are all disengaged. As a result, with the aid of freewheel  14 , impeller  10  is free-wheeling. Consequently, no torque is transmitted, and the torque transmission device is in the freewheeling state. 
   In response to a pressurization of first pressure channel  17 , the entire torque transmission device is traversed by flow, second pressure channel  18  functioning as outflow for the operating medium. In response to pressurization of first pressure channel  17 , impeller  10  in the representation according to the figure is pressed to the right; as a result third coupling  29  is engaged, and impeller  10  is connected in a torsion ally fixed manner to second housing part  6  and thus to housing  4 . First coupling  27 , as well as second coupling  28  are disengaged, so that turbine  9  is able to rotate freely relative to impeller  10  and housing  4 . For that reason, as is the case when working with torque converters or Föstinger couplings, it is customary for turbine  9  to be driven solely by the fluid flow produced by the relative motion of turbine  9  with respect to impeller  10 . In this operating mode, the torque transmission device is in torque converter operation. 
   If second pressure channel  18  is pressurized, so that the torque transmission device is traversed by flow from second pressure channel  18  as inflow and from first pressure channel  17  as outflow into the operating medium, then impeller  10  in the representation according to the figure is pressed to the left, so that third coupling  29  is disengaged and second coupling  28  is engaged. Thus, impeller  10  is connected via flange  19  and consequently via tensional vibration damper  21  to housing  4 . At the same time, in the representation according to the figure, turbine  9  is pressed to the right, so that first coupling  27  is likewise engaged. Thus, turbine  9 , as well as impeller  10  grip around flange  19  and, as a result, are rotationally fixed to one another. Flange  19  is connected, in turn, by way of tensional vibration damper  21  to housing  4 , so that here as well, a connection that is substantially stiff, though slightly rotatable in response to spring force, is produced between impeller  10  and turbine  9 , as well as housing  4 . Thus, the function of the torque transmission device as torque converter is by-passed in this case; the torque transmission device is in lock-up operation. Thus, together, first and second coupling  27 ,  28  form the lockup clutch. 
   In torque converter operation, impeller  10 , along with the corresponding bearing parts, as well as housing  4  form a unit which is rotatable relative to turbine  9  having the corresponding bearing parts and input shaft  3 . Both subsystems are substantially rigid and only coupled to one another via the hydraulic oil. For that reason, the vibration behavior of the overall system is determined by the particular rotational inertias of the individual systems, and the coupling by the fluid. In lock-up operation, turbine  9 , as well as impeller  10 , along with the corresponding bearing parts and output shaft  3 , as well as flange  19 , are substantially rigidly interconnected and form one combined rotationally inert system. This system is rotatable connected against spring force by way of tensional vibration damper  21  to housing  4 . On the whole, therefore, a system is created that is capable of damped tensional vibrations, whose characteristic vibration properties are determined from the ratio of the masses of the previously described subsystems, and the rigidity of the spring coupling is determined by the tensional vibration damper. 
   The claims filed with the application are proposed formulations and do not prejudice the attainment of further patent protection. The applicant reserves the right to claim still other combinations of features that, so far, have only been disclosed in the specification and/or the drawings. 
   The antecedents used in the dependent claims refer, by the features of the respective dependent claim, to a further embodiment of the subject matter of the main claim; they are not to be understood as renouncing attainment of an independent protection of subject matter for the combinations of features of the dependent claims having the main claim as antecedent reference. 
   Since, in view of the related art on the priority date, the subject matters of the dependent claims may form separate and independent inventions, the applicant reserves the right to make them the subject matter of independent claims or of divisional applications. In addition, they may also include independent inventions, whose creation is independent of the subject matters of the preceding dependent claims. 
   The exemplary embodiments are not to be understood as limiting the scope of the invention. Rather, within the framework of the present disclosure, numerous revisions and modifications are possible, in particular such variants, elements and combinations and/or materials, which, for example, by combining or altering individual features or elements or method steps described in connection with the general description and specific embodiments, as well as the claims, and contained in the drawings, may be inferred by one skilled in the art with regard to achieving the objective, and lead, through combinable features, to a new subject matter or to new method steps or sequences of method steps, also to the extent that they relate to manufacturing, testing, and operating methods.