Abstract:
The invention relates to a variable displacement pump having two connections for supplying and withdrawing a volume flow guided by said variable displacement pump. The invention is characterized in that this variable displacement pump includes an additional connection for providing and additional volume flow.

Description:
BACKGROUND 
       [0001]    The invention relates to a variable displacement pump with two connections for supplying and withdrawing a volume flow conveyed by said variable displacement pump. The invention further relates to a method for operating such a variable displacement pump. 
         [0002]    An electrohydraulic pressure supply is known from the German patent publication DE 199 30 648 A1 comprising an electric drive motor that is speed controllable and a variable displacement pump, with its intake volume being adjustable by an adjusting member comprising connection lines and consumer connections. 
       SUMMARY 
       [0003]    The objective of the invention is to simplify the provision of volume flows that are adjustable independent from each other. 
         [0004]    The objective is attained in a variable displacement pump with two connections for supplying and withdrawing a volume flow conveyed by the variable displacement pump such that the variable displacement pump has an additional connection for providing an additional volume flow. This way, in a simple fashion the supply of two hydraulic consumers is possible with different, variable requirements for the volume flow. The hydraulic consumers may represent for example clutch parts of a duplex clutch. The variable displacement pump is preferably connected permanently and in a driving fashion to a drive device, for example to a drive device of an internal combustion engine. The volume flows provided to the connection and the additional connection are advantageously adjustable separately from each other. 
         [0005]    A preferred exemplary embodiment of the variable displacement pump is characterized in that the variable displacement pump can be adjusted by physical signals that are adjustable independent from each other such that the volume flows can be adjusted at two of the total of three connections independent from each other. One of the connections represents a reservoir connection, via which a hydraulic medium to be conveyed is taken in. The hydraulic medium represents for example hydraulic oil, which is also called oil, for short. The two other connections represent inputs or outputs of the variable displacement pump. The adjustment may occur two-dimensionally or three-dimensionally. 
         [0006]    Another preferred exemplary embodiment of the variable displacement pump is characterized in that the variable displacement pump can be adjusted by physical signals that are adjustable independent from each other such that the volume flows at two of the total of three connections can be inverted with regards to their direction of flow. The inversion of the direction of flow can occur particularly advantageously without inverting the direction of rotation of the conveyance device of the variable displacement pump. The type of adjustment signal depends on the type and/or the design of the variable displacement pump. 
         [0007]    Other preferred exemplary embodiments of the invention of the variable displacement pump are characterized in that the variable displacement pump is embodied as a cell pump or as a radial piston pump. In the cell pump and the radial piston pump the adjustment occurs preferably by displacing axes of blades towards a contour of a pump housing. Here, different directions of displacement determine the volume flow of respectively one pump outlet. 
         [0008]    Another preferred exemplary embodiment of the variable displacement pump is characterized in that the variable displacement pump is embodied as an axial piston pump. In the axial piston pump the adjustment of the volume flow results preferably from tilting the swashplate or swash-disk, which causes an axial motion of the piston of the pump. Here, two tilting directions act upon the volume flows, which are provided at the connection and the additional connection. 
         [0009]    In a method for operating an above-described variable displacement pump the above-stated objective is alternatively or additionally attained such that respectively one volume flow is provided to two connections. The two volume flows can be adjusted separately and independent from each other. The two volume flows that can be adjusted independent from each other may be used for operating a duplex clutch, for example. 
         [0010]    A preferred exemplary embodiment of the method of the invention is characterized in that the volume flows provided at the two connections are adjusted independent from each other by physical signals that can be independently adjusted. The type of adjustment signals depend here on the type of variable displacement pump used. 
         [0011]    Another preferred exemplary embodiment of the method is characterized in that at least one of the two volume flows provided at the two connections can be inverted with regards to its direction of flow. The inversion of the direction of flow occurs particularly advantageously without inverting the direction of rotation of the variable displacement pump. 
         [0012]    Another preferred exemplary embodiment of the method is characterized in that the volume flows provided at the two connections are combined to a third volume flow. This way, the functionality of the variable displacement pump according to the invention can be further increased. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Additional advantages, features, and details of the invention are discernible from the following description, in which different exemplary embodiments are described in detail with reference to the drawings. Shown are: 
           [0014]      FIG. 1  a largely simplified illustration of a variable displacement pump according to a first exemplary embodiment; 
           [0015]      FIG. 2  a similar illustration as in  FIG. 1  with additional blades displayed; 
           [0016]      FIG. 3  a variable displacement pump of  FIG. 2  with lines and arrows indicating the operation of the variable displacement pump; 
           [0017]      FIG. 4  a perspective illustration of a variable displacement pump embodied as an axial piston pump; 
           [0018]      FIG. 5  the variable displacement pump of  FIG. 4  in a different perspective; and 
           [0019]      FIG. 6  a simplified illustration of a variable displacement pump embodied as a radial piston pump. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]      FIGS. 1 to 3  show in a simplified fashion a variable displacement pump  1  with a housing  3 . A rotor  5  is rotationally driven in the housing  3 . In  FIG. 1  it is indicated by double arrows in the center of the rotor  5  that said rotor  5  is movable inside the housing  3  in order to adjust the conveyed volume or the intake volume of the variable displacement pump  1 . Directions of adjustment are indicated in  FIG. 1  by the lines  14  to  18 , along which the rotor  5  can be moved inside the housing  3 . 
         [0021]    The variable displacement pump  1  comprises at the housing  3  a reservoir connection  10 , a connection  11 , and an additional connection  12 . The reservoir connection  10  allows the supply of hydraulic media from a hydraulic medium reservoir (not shown). 
         [0022]    The two connections  11  and  12  are advantageously adjustable independent from each other. The connection  11  is connected for example to a slave cylinder of a first clutch part of a duplex clutch. The connection  12  is then advantageously connected to a slave cylinder of a second clutch part of the duplex clutch. 
         [0023]    The connections  10  to  12  shown represent areas in which the connections  10  to  12  are provided at the housing  3 . Here, the connections  10  to  12  may be arranged in a casing area of the housing  3 . However, the connections  10  to  12  may also be arranged in a facial area and/or a face of the housing  3 . 
         [0024]    It is discernible from  FIG. 2  that the rotor comprises slots for the radially mobile arrangement of a total of eight blades  20 . The blades  20  are arranged with their radially internal ends in the rotor slots. With their radially exterior ends the blades  20  contact an interior contour of the housing  3 . 
         [0025]    An arrow  19  in  FIG. 3  indicates that the rotor  5  is driven in the clockwise direction. During operation the rotor  5  rotates with the blades  20  in a housing  3 . An adjustment of the volume flows, provided by the variable displacement pump during operation, occurs by displacing the rotor  5  in reference to the housing  3 . 
         [0026]    The displacements indicated by the double arrows in the center of the rotor  5  shown in  FIGS. 1 and 2  may be initiated from the outside at the rotor  5  or the housing  3 . In a rotationally driven rotor  5  it may be beneficial to implement the relative motion for adjusting the volume flows provided by the adjustment pump  1  by displacements at the housing  3 . 
         [0027]    The drive of the rotor  5  may for example occur by a fixed coupling to a drive train of a motor vehicle. Although the displacement for adjusting the volume flows can occur both by the housing  3  as well as the rotor  5 , in the following the adjustment is explained based on an adjustment of the rotor  5 . 
         [0028]    Dot-dash lines  21  and  22  in  FIG. 3  indicated axes of motion along which the rotor  5  can be moved in order to adjust the volume flows provided at the connections  11  and  12 . Arrows  23  and  24  represent indicators for the direction of the pump for a first consumer, for example a first clutch part of a duplex clutch. Here, the dot-dash line  21  represents a neutral line for the first consumer. The arrows  25  and  26  are indicators for the direction of the pump for a second consumer, for example for a second clutch part of the duplex clutch. Here, the dot-dash line  22  represents a neutral line for the second consumer. 
         [0029]    When the rotor  5  is displaced along the dot-dash line  21  the volume flow of the first consumer remains zero. Similarly, the volume flow of the second consumer remains zero when the rotor  5  is displaced along the dot-dash line  22 . 
         [0030]    When the rotor  5  is precisely in the middle, as shown in  FIG. 3 , it is arranged on both neutral lines  21 ,  22 . Then the volume flows conveyed by the variable displacement pump  1 , for example the volume flows provided at the two connections  11  and  12 , are zero independent from a speed of the rotor  5 . 
         [0031]    When the rotor  5  is moved from the neutral line  21  upwards towards the left, the hydraulic medium or fluid is suctioned at the connection  11  in the direction towards the variable displacement pump as indicated by the motion arrow  23 . Additionally, at the same direction of rotation during a motion of the rotor  5  towards the right bottom, here fluid or hydraulic medium is pushed out of the variable displacement pump at the connection  11  as indicated by the motion arrow  24 . 
         [0032]    If the rotor  5  is moved from the neutral line  22  upwards towards the right, the fluid is suctioned at the connection  12  in the direction towards the variable displacement pump, as indicated by the motion arrow  25 . Additionally, at an identical direction of rotation during a motion of the rotor  5  downwards towards the left fluid is pushed out of the variable displacement pump at the connection  12 , as indicated by the motion arrow  26 . 
         [0033]      FIG. 4  shows a variable displacement pump  31  in various illustrations in a perspective fashion. The variable displacement pump  31  is embodied as an axial piston pump and can be similarly adjusted like the above-described variable displacement pump  1 . 
         [0034]    The axial piston pump  31  comprises a housing  33  with a disk  34 . A revolver  35  is equivalent to the rotor ( 5  in  FIG. 1 ) and can be driven in a rotary fashion. Pistons  36  are guided in a movable fashion in an axial direction back and forth in the revolver  35 . 
         [0035]    The pistons  36  rest via sliding shoes  37  on a swashplate  38 . Levers  39  symbolizing the axes are provided at the swashplate  38  in order to allow pivoting the swashplate  38  for adjusting the conveyed volume or the intake volume of the variable displacement pump. 
         [0036]    A reservoir connection  40  is provided in the disk  34 . Furthermore, a connection  41  and an additional connection  42  are provided in the disk  34 . 
         [0037]    Compared to the above-described variable displacement pump  1 , the volume flows of the variable displacement pump  31  provided at the connections  41  and  42  are adjusted via an incline of the swashplate  38  instead of a displacement. During operation of the variable displacement pump  31  the revolver  35  rotates in reference to the disk  34  with the connections  40  to  42 . Here, the revolver  35  also rotates in reference to the swashplate  38 , with the rotating revolver  35  entraining the piston  36 . 
         [0038]    The drive of the revolver  35  is not shown and can occur in various fashions. The drive of the revolver  35  can occur via a shaft, for example, extending through the swashplate  38  or through the disk  34 . Alternatively the piston  35  can be driven directly via gears embodied on the revolver  35  itself. 
         [0039]    The incline of the swashplate  38  can be adjusted in a three-dimensional fashion. The control during the adjustment of the variable displacement pump  31  occurs similar to the above-described adjustment of the cell pump  1 . Contrary to the cell pump  1  the axial piston pump  31  is not deflected by tilting. 
         [0040]    The adjusting or setting of the variable displacement pump  31  occurs with a separate mechanical component, with its connection here being shown only schematically in the form of levers  39 . The variable displacement pump  31  shown in  FIGS. 4 and 5  comprises three pistons  36  in the revolver  35 . Contrary to the version shown, preferably more than three pistons  36  are provided in the revolver  35 , for example five or six pistons  36 , guided back and forth in an axially movable fashion. 
         [0041]      FIG. 5  shows the axial piston pump  31  from a slightly modified perspective with the disk  34  being lifted off. Due to the fact that the disk  34  comprises the connections  40  to  42  the disk  34  is also called a connection disk. The support  45  of the swashplate  38  occurs via a spherical geometry as shown in  FIG. 5  as an example. 
         [0042]      FIG. 6  shows a variable displacement pump  51  embodied as a radial piston pump. The radial piston pump  51  comprises a housing  53  in which a rotor  55  is driven rotationally in the clockwise direction, as indicated by an arrow in the center of the rotor  55 . In the rotor  55 , radially at the outside a total of eight pistons  56  are guided movable back and forth. 
         [0043]    The radially aligned pistons  56  are each arranged with their radially interior end in the rotor  55 . With their respectively radial exterior end the pistons  56  contact an internal contour of the housing  53 , perhaps with sliding shoes interposed. In a similar fashion as the cell pump  1  shown in  FIGS. 1 to 3 , the housing  53  comprises a reservoir connection  60 , a connection  61 , and an additional connection  62 . 
         [0044]    During operation of the radial piston pump  51  the pistons  56  are pushed radially inwardly. The adjustment of the volume flows provided at the connections  61  and  62  occurs similar to the cell pump  1  shown in  FIGS. 1 to 3  via a translation between the housing  53  and the rotor  55 . 
       LIST OF REFERENCE CHARACTERS 
       [0000]    
       
           1  variable displacement pump 
           3  housing 
           5  rotor 
           10  reservoir connection 
           11  connection 
           12  additional connection 
           14  line 
           15  line 
           16  line 
           17  line 
           19  arrow 
           20  blade 
           21  dot-dash line 
           22  dot-dash line 
           23  arrow 
           24  arrow 
           25  arrow 
           26  arrow 
           31  variable displacement pump 
           33  housing 
           34  disk 
           35  revolver 
           36  piston 
           37  sliding shoe 
           38  swashplate 
           39  lever 
           40  reservoir connection 
           41  connection 
           42  additional connection 
           45  support 
           51  variable displacement pump 
           53  housing 
           55  rotor 
           56  piston 
           60  reservoir connection 
           61  connection 
           62  additional connection