Abstract:
The invention relates to a hydrodynamic torque converter comprising a driving pump wheel, a driven turbine wheel, and a guide wheel, which has guide wheel blades. In order to create a hydrodynamic torque converter, which requires less installation space than conventional torque converters and is producible cost-effectively, the guide wheel blades are attached to the guide wheel such that they can move between a throughflow position and a guide position.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This patent application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/689,756, filed Jun. 10, 2005, which application is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The invention relates to a hydrodynamic torque converter comprising a driving pump wheel, a driven turbine wheel, and a guide wheel, which comprises the guide wheel blades. 
   BACKGROUND OF THE INVENTION 
   In conventional hydrodynamic torque converters, the guide wheel is supported rotatably in one direction of rotation. The other direction of rotation is blocked by a freewheel in order to prevent the guide wheel from twisting against the direction of rotation of the pump wheel and the turbine wheel. A medium stream delivered from the pump wheel via the turbine wheel is supported against the guide wheel blades of the guide wheel blocked by the freewheel. If the pump wheel and the turbine wheel have approximately the same speed, then the direction of the medium stream changes such that it flows towards the guide wheel blades from the rear side and the guide wheel starts to rotate along. 
   SUMMARY OF THE INVENTION 
   It is the object of the invention to create a hydrodynamic torque converter comprising a driving pump wheel, a driven turbine wheel and a guide wheel, which comprises guide wheel blades, wherein said hydrodynamic torque converter requires less installation space as compared to conventional torque converters and is producible cost-effectively. 
   The object is attained in a hydrodynamic torque converter comprising a driving pump wheel, a driven turbine wheel and a guide wheel, which comprises guide wheel blades, by attaching the guide wheel blades to the guide wheel such that they can move between a throughflow position and a guide position. In the guide position, a medium stream delivered from the pump wheel via the turbine wheel is supported against the guide wheel blades. This brings about a backpressure, which results in increasing the rotary force of the blades of the turbine wheel. The medium stream is guided from the guide wheel blades at an advantageous angle back to the blades of the pump wheel. If the pump wheel and the turbine wheel have approximately the same speed, then the direction of the medium stream changes such that it flows towards the guide wheel blades in another direction, for example, towards their rear side. Due to the incident flow from the other direction, the guide wheel blades move from their guide position into their throughflow position, in which they enable an unobstructed medium flow through the guide wheel. The rotatable bearing of the guide wheel and the freewheel can be omitted. 
   A preferred embodiment of the torque converter includes a guide wheel that is stationary in relation to the pump wheel and the turbine wheel. The guide wheel is fixed, for example, to a stationary housing structure or to a fixed supporting structure of a motor vehicle. 
   In another preferred embodiment of the torque converter, the guide wheel blades are supported on the guide wheel such that they can swivel between the throughflow position and the guide position. The bearing of the guide wheel blades is implemented, for example, with the help of pins, which are fixed to the guide wheel. 
   In another embodiment of the torque converter, the guide wheel comprises an inner ring, from which a flange stretches radially outwards, on the radially outer area of which the guide wheel blades are swivelably supported. The bearing of the guide wheel blades is implemented, for example, with the help of pins, which are fixed to the flange. 
   In another embodiment of the torque converter, the flange includes a limit stop for a foot, which runs from the associated guide wheel blade. The limit stops serve for fixing the guide wheel blades in their guide position. 
   In another preferred embodiment of the torque converter, the guide wheel comprises an outer ring, which is connected to the flange using connecting webs. This increases the stability of the guide wheel. 
   Another preferred embodiment of the torque converter includes one limit stop for each guide wheel blade on the outer ring. The limit stops serve for fixing the guide wheel blades in their guide position. 
   Another preferred embodiment of the torque converter is arranged such that the guide wheel blades rest against one another in their throughflow position. The guide wheel blades are preferably arranged in their throughflow position in the peripheral direction of the flange in order to enable an unobstructed passage of the medium stream. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional advantages, features and details of the invention are specified in the following description, in which different example embodiments are described in detail with reference to the drawing. The features mentioned in the claims and in the description can thereby be essential to the invention either individually or in any combination thereof. The drawing illustrates: 
       FIG. 1  illustrates the view of a section through a guide wheel according to a first embodiment; 
       FIG. 2  illustrates the top view of a section of the guide wheel shown in  FIG. 1 , wherein the guide wheel blades are located in their guide position; 
       FIG. 3  illustrates the same view as in  FIG. 2  of the guide wheel shown in  FIG. 1 , wherein the guide wheel blades are located in their throughflow position; 
       FIG. 4  illustrates the view of a section through a guide wheel according to a second embodiment; and, 
       FIG. 5  illustrates a top view of a section of the guide wheel shown in  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention relates to a hydrodynamic torque converter. The hydrodynamic torque converter is combined with a planetary gear in an automatic gearbox of a motor vehicle. It replaces a mechanical friction coupling as a starting clutch and expands, as a dynamic torque converter, the transmission ratio range of the planetary gear connected downstream. The hydrodynamic torque converter comprises a pump wheel driving at motor rotation speed, a driven turbine wheel, and a guide wheel. The pump wheel, turbine wheel, and the guide wheel are embodied as bent blade wheels and run in a closed housing filled with hydraulic oil. 
     FIGS. 1 to 3  illustrate a guide wheel  1  in different views and positions thereof. The guide wheel  1  comprises an inner ring  2 , which substantially has the shape of a hollow circular cylinder. The inner ring  2  serves for fixing the guide wheel  1  to a suitable supporting structure. A flange  4  stretches radially outwards from the inner ring  2 . Guide wheel blades  6 ,  7 ,  8  are swivelably supported on the radially outer area of the flange  4 . 
   The structure of the guide wheel blades is explained in the following on the basis of the guide wheel  7  by way of example. The guide wheel blade  7  comprises a blade body  10 , which is designed with a bent shape and a front side  11  and also a rear side  12 . The guide wheel blade  7  is swivelably supported on the flange  4  with the help of a pin  14 . The pin  14  comprises a head  15 , from which a bolt  16  runs. The bolt  16  stretches through a throughhole  17 , which is cut out in the guide wheel blade  7 . A bearing disk  18  is arranged between the head  15  of the pin  14  and the guide wheel blade  7 . Furthermore, the bolt  16  of the pin  14  stretches through a throughhole  20 , which is cut out in the radially outer area of the flange  4 . The end of the bolt  16 , said end opposing to the head  15  of the pin  14 , protrudes over the flange  4  on the side of the flange  4 , said side being turned away from the guide wheel blade  7 . The pin  14  is fixed to the flange  4  of the guide wheel  1  in the axial direction with the help of a retaining ring  21 . 
   On its side opposite to the blade body  10 , the guide wheel blade  7  comprises a foot  24 . In the guide position of the guide wheel blade  7  illustrated in  FIG. 2 , the foot  24  rests against a limit stop  26 , which is fixed to the flange  4  of the guide wheel  1 . The limit stop  26  prevents an additional twist of the blade body  10  if the medium stream flows towards the front side  11  of the blade body  10 . If the medium stream flows towards the blade body  10  from its rear side  12 , then the blade body  10  deviates from the guide position illustrated in  FIG. 2  into its throughflow position shown in  FIG. 3 . In said throughflow position, the guide wheel blade  7  rests against the adjoining guide wheel blade  6 . Similarly, the guide wheel blade  8  rests against the guide wheel blade  7  in the throughflow position. 
     FIGS. 4 and 5  illustrate different views of a guide wheel  41  according to another embodiment. The guide wheel  41  comprises an inner ring  42 , from which a flange  44  stretches radially outwards. Guide wheel blades  47 ,  48  are swivelably supported on the radially outer area of the flange  44 . 
   The structure of the guide wheel blades is explained in the following on the basis of the guide wheel blade  47  by way of example. The guide wheel blade  47  has a bent blade body  50  with a front side  51  and a rear side  52 . The guide wheel blade  47  is swivelably attached to the flange  44  of the guide wheel  41  with the help of a pin  54 . The pin  54  comprises a head  55 , from which a bolt  56  runs. The bolt  56  stretches through a throughhole  57 , which is cut out in the guide wheel blade  47 . A bearing disk  58  is arranged between the head  55  of the pin  54  and the guide wheel blade  47 . The end of the bolt  56 , the end being turned away from the head  55 , is inserted through a throughhole  60 , which is cut out in the radially outer area of the flange  44  of the guide wheel  41 . The end of the pin  54 , the end being turned away from the head  55 , is fixed to the flange  44  of the guide wheel  41  in the axial direction with the help of a retaining ring  61 . 
   A connecting web  64  stretches radially outwards from the flange  44  of the guide wheel  41 . The connecting web  64  and other connecting webs (not illustrated) stretch in the radial direction between the flange  44  and an outer ring  65 , which is arranged coaxially or concentrically to the inner ring  42 . Limit stops  66 ,  67  for the guide wheel blades  47 ,  48  are provided in the radially inner area of the outer ring  65 . The limit stops  66 ,  67  prevent the guide wheel blades  47 ,  48  from twisting in the clockwise direction beyond the position illustrated in  FIG. 5 . Due to the limit stops  66  and  67 , the guide wheel blades  47  and  48  are fixed in their guide position if the medium stream flows towards their front side  51 . If the medium stream flows towards the rear side  52  of the guide wheel blade  47 , then the latter moves out of the guide position illustrated using continuous lines into the throughflow position indicated by the dashed line. In the throughfow position, the guide wheel blades partially rest against one another. In addition, the guide wheel blades are substantially arranged in the peripheral direction in the throughflow position indicated by the dashed line. 
   During start-up, the oil located between the blades of the pump wheel flows outwards due to the centrifugal force, is deflected and hits on the blades of the stopped turbine wheel. The kinetic energy of the oil stream is converted into a rotary force. The turbine wheel starts to rotate and delivers kinetic energy to the planetary gear connected downstream. The oil emerging from the turbine wheel against the direction of rotation now hits on the guide wheel and is supported against the blades of the guide wheel, said blades being bent opposite to the pump wheel and the turbine wheel and could turn the guide wheel against the direction of rotation of the pump wheel and the turbine wheel. The oil is now supported against the guide wheel blades, which are located in their guide position and rest against the associated limit stops. This brings about a strong backpressure, which results in increasing the rotary force of the blades of the turbine wheel. The oil stream is guided using the guide wheel blades at an advantageous angle back towards the blades of the pump wheel. 
   The higher the speed of the turbine wheel, the smaller is the speed difference between the pump wheel and the turbine wheel. The oil stream now impinges on the guide wheel blades at another angle. This reduces the support force and thus the additional force on the blades of the turbine wheel. Should the pump wheel and the turbine wheel have approximately the same speed, the direction of the oil stream changes. The oil stream now flows towards the guide wheel blades from their rear side and the latter deviate from their guide position into their throughflow position. There is no more dynamic pressure. No additional rotary force acts on the turbine wheel. Therefore no more torque multiplication will take place. The torque converter then functions as a hydrodynamic coupling. 
   LIST OF REFERENCE NUMERALS 
   
       
         1  Guide wheel 
         2  Inner ring 
         4  Flange 
         6  Guide wheel blade 
         7  Guide wheel blade 
         8  Guide wheel blade 
         10  Blade body 
         11  front side 
         12  Rear side 
         14  Pin 
         15  Head 
         16  Bolt 
         20  Throughhole 
         18  Bearing disk 
         20  Throughhole 
         21  Retaining ring 
         24  Foot 
         26  Limit stop 
         41  Guide wheel 
         42  Inner ring 
         44  Flange 
         47  Guide wheel blade 
         48  Guide wheel blade 
         50  Blade body 
         51  Front side 
         52  Rear side 
         54  Pin 
         55  Head 
         56  Bolt 
         57  Throughhole 
         58  Bearing disk 
         60  Throughhole 
         61  Retaining ring 
         64  Connecting web 
         65  Outer ring 
         66  Limit stop 
         67  Limit stop