Patent Publication Number: US-11022113-B2

Title: Connection assembly with feed pump and elastic element

Description:
This application claims priority under 35 U.S.C. § 119 to patent application number DE 10 2018 208 068.2, filed on May 23, 2018 in Germany, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The disclosure relates to a connection assembly as per the following description. 
     DE 10 2007 011 644 B4 has disclosed an axial piston machine having a connection assembly which comprises a feed pump. The connection assembly is designed such that only a small number of parts have to be changed in order to adapt the connection assembly to feed pumps with different delivery capacities. 
     An advantage of the present disclosure consists in that even fewer parts have to be changed in order to adapt the connection assembly to feed pumps with different delivery capacities. Specifically, no changes need to be made to the cover, and/or intermediate rings provided there can be omitted. Furthermore, the connection assembly is completely leak-tight in the region of the feed pump even if parts with unfavorable dimensions are combined with one another within the manufacturing tolerance. 
     According to the following description, it is proposed that an elastic element is installed under preload between the cover and the receiving part such that a corresponding preload force is supported at least indirectly on the main body via the sealing surface. The stated parts of the pump assembly preferably jointly define the sealing plane. The stated preload force is, in the region of the receiving part and/or of the outer part, supported on the main body preferably in static fashion. In the region of the inner part, the preload force is supported on the main body preferably by means of the hydrostatic forces that arise during operation, wherein, in the standstill state, substantially no force is supported by the inner part. The force acting on the pump assembly via the sealing surface in the direction of the axis of rotation is preferably supported exclusively via the elastic element. It is preferable for the receiving part and the cover to be arranged with a spacing to one another across their entire extent. The outer part and the inner part bear preferably sealingly against the base of the first recess or against a closure plate arranged there. The first and/or the second recess are preferably each of circular cylindrical design and arranged parallel to the axis of rotation. It is preferable for the first and the second recess to be arranged eccentrically with respect to one another. 
     Advantageous refinements and improvements of the disclosure are specified in the following description. 
     SUMMARY 
     Provision may be made for the elastic element to be formed as a separate component. The receiving part and/or the cover are formed so as to be substantially rigid in relation thereto, wherein these are preferably composed of metal, in particular steel, cast iron or aluminum. The preload force of the elastic element can thus be easily set such that no leaks occur in the region of the sealing surface. In particular, it is also possible to realize high preload forces, such that the elastic element can accommodate even high hydraulic forces. The elastic element is preferably composed of steel, most preferably of hardened spring steel. 
     Provision may be made for the elastic element to be formed as a single piece. It can thus be produced particularly easily. It is preferably envisaged for the elastic element to be bent from a wire or punched from a metal sheet. 
     Provision may be made for the elastic element to annularly surround the axis of rotation. Said elastic element is preferably in the form of a circular ring. Its outer ring diameter amounts to preferably between 80% and 95% of the outer diameter of the receiving part. The dimensions of the elastic element are thus configured to be as large as possible. The elasticity of the elastic element can thus be easily adjusted, wherein said elastic element can simultaneously transmit high forces. 
     Provision may be made for the elastic element to be formed in the manner of an ondular washer. The elastic element preferably has a constant, for example rectangular, cross-sectional shape over its circumference. Said elastic element runs along its circumference, preferably in undulating bent fashion. 
     Provision may be made for the elastic element to be formed so as to be discontinuous in a circumferential direction. Said elastic element accordingly has the form of a slotted ring. This yields a defined stiffness of the elastic element, which is defined exclusively by the bending stiffness, which is easy to determine by calculation, of the individual undulating portions. 
     Provision may be made for the elastic element to be received in a groove, which runs in encircling fashion annularly around the axis of rotation, in the receiving part. The position of the elastic element transversely with respect to the axis of rotation is thus defined in form-fitting fashion. The preload force acts centrally on the receiving part, such that there is no risk of said receiving part becoming jammed in the second recess or the mobility of said receiving part being impeded in some other way. 
     Provision may be made for the depth of the groove measured in the direction of the axis of rotation to be smaller than the corresponding height of the unbraced elastic element. Said depth is preferably also smaller than the corresponding height of the elastic element in the fully assembled state. It is achieved in this way that the cover bears exclusively against the elastic element but not against the receiving part. 
     Provision may be made for the pump assembly to bear via a separate closure plate against the main body, wherein the closure plate has at least two apertures which open out in each case between the inner part and the outer part, wherein the closure plate is connected rotationally conjointly to the main body, wherein at least one aperture is fluidically connected to an associated fluid connection. The closure plate is preferably formed as a planar plate of constant thickness. The apertures are preferably of kidney-shaped form. The closure plate is preferably composed of brass or of coated steel, in particular of manganese-phosphated steel. 
     Provision may be made for an outer circumferential surface of the closure plate and an outer circumferential surface of the receiving part to be formed in alignment with one another in the direction of the axis of rotation. Said outer circumferential surfaces are preferably of circular cylindrical form with respect to the axis of rotation. 
     Provision may be made for at least one aperture to be assigned a third recess which is arranged on the base of the first recess. Additional pressure equalization between the individual pressure chambers of the feed pump is achieved in this way. The apertures in the closure plate already give rise to similar pressure equalization. The circumferential shape of the third recesses is, preferably as viewed in the direction of the axis of rotation, formed so as to be congruent with the circumferential shape of the respectively associated aperture in the closure plate. 
     Protection is also asserted for a collection which comprises at least two connection assemblies according to the disclosure, wherein the main bodies, the covers and the drive shaft of all connection assemblies are of identical form, wherein the outer parts and the inner parts of the various connection assemblies differ, wherein an external shape of the receiving part is of identical form in all connection assemblies, wherein an internal shape of the receiving part is of different form in the various connection assemblies. The outer parts and the inner parts of the various connection assemblies preferably differ with regard to the width measured in the direction of the axis of rotation. 
     It is self-evident that the features mentioned above and the features yet to be discussed below may be used not only in the respectively specified combination but also in other combinations or individually without departing from the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be discussed in more detail below on the basis of the appended drawings, in which: 
         FIG. 1  shows a longitudinal section of a connection assembly according to the disclosure; 
         FIG. 2  shows a perspective view of the inner part, of the outer part and of the drive shaft; 
         FIG. 3  shows a further perspective view of the assembly as per  FIG. 2 ; 
         FIG. 4  shows a perspective view of the receiving part; 
         FIG. 5  shows a further perspective view of the receiving part; 
         FIG. 6  shows a perspective view of the elastic element; and 
         FIG. 7  shows a block diagram of a vane pump including an inner part and an outer part. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a longitudinal section of a connection assembly  10  according to the disclosure. The connection assembly  10  is provided for use in the axial piston pump as per the German patent application with the file reference 102017213457.7. The entire content of said patent application is referred to and incorporated into the content of the present application. The connection assembly  10  is, in the cited patent application, referred to as “housing cover”, wherein the term “connection plate” is also common. 
     The connection assembly  10  comprises a main body  20 , which is produced for example in a casting process. The main body  20  forms at least one fluid connection  21 , wherein, in  FIG. 1 , only the suction connection is visible, whereas the pressure connection is not visible. In the direction of an axis of rotation  11 , the main body  20  is extended through by a drive shaft  30 , which in the present case comprises a first and a second shaft part  31 ;  32 , which shaft parts are connected to one another rotationally conjointly with respect to the axis of rotation  11  for example by means of a spline toothing, a parallel-key driving arrangement or a hexagonal connection. The first shaft part  31  bears the cylinder drum of the axial piston machine, wherein the second shaft part  32  bears the feed pump  40 . The feed pump  40  is, in the present case, in the form of an internal gear pump, wherein it may also be in the form of a vane-type pump. In both cases, the feed pump comprises an inner part  41 , which is connected rotationally conjointly to the drive shaft  30 . The inner part  41  is annularly surrounded by an outer part  42 . Between the inner part  41  and the outer part  42 , there are multiple pressure chambers, the volume of which changes when the drive shaft  30  rotates. In the case of an internal gear pump, said pressure chambers are delimited with respect to one another in fluid-tight fashion by toothings on the inner and outer parts  41 ;  42 . In the case of a vane-type pump (as shown in  FIG. 7 ), said pressure chambers are delimited with respect to one another in fluid-tight fashion by radially movable vanes  45 . 
     The connection assembly  10  according to the disclosure has the advantage that it can be adapted in a flexible manner to different feed pumps, which differ in particular with regard to the width of the inner and of the outer part  41 ;  42  in the direction of the axis of rotation  11 . Here, the main body  20 , the drive shaft  30  and the cover  80  may be of identical form in all structural variants. Differences arise only in the case of the inner and the outer part  41 ;  42  in order to realize the desired delivery capacity. The internal shape of the receiving part  50  is formed in a correspondingly adapted manner, wherein the external shape of the receiving part  50  is identical in all structural variants. 
     The inner part  41 , the outer part  42  and the receiving part  50  together form a pump assembly  12 , wherein all of the stated parts have a common planar sealing surface  13 . The receiving part  50  is received in a second recess  22  of the main body, which is preferably of circular cylindrical form with respect to the axis of rotation  11 . By means of a cylindrical pin  55 , the receiving part  50  is secured against rotation about the axis of rotation  11 . In the present case, the sealing surface  13  bears, via a separate closure plate  70 , against the planar base of the second recess  22 , wherein said sealing surface may also bear directly against said base. The closure plate  70  is formed in the manner of a planar plate of constant thickness, which is composed for example of brass. It is likewise secured against rotation by means of the cylindrical pin  55  (see  FIG. 2 ). 
     The outer part  42  is received in a first recess  51  in the receiving part  50 . The first recess  51  is of circular cylindrical form, wherein it is arranged eccentrically with respect to the axis of rotation  11 . In the case of the present internal gear pump, the outer part  42  is received rotatably there. In the case of a vane-type pump, the outer part  42 , specifically the stroke ring, is received rotationally fixedly there. 
     The receiving part  50  is covered at least in certain portions by a cover  80 , wherein the cover  80  is screwed to the main body  20 . The cover  80  may, as illustrated here, have an opening, such that a through drive to a directly mounted hydraulic machine is possible. The cover may however also be a closed cover. Between the cover  80  and the main body  20 , there is installed a sealing ring  81  for preventing an escape of fluid. The elastic element  60  according to the disclosure is installed under preload between the cover  80  and the receiving part  50 . The corresponding preload force acts in the direction of the axis of rotation  11 , wherein said preload force is supported on the cover  80  and, by way of the physical contact, on the sealing surface  13 . The receiving part  50  has, in the direction of the axis of rotation  11 , a certain movement clearance in the second recess  22 , such that the entire pump assembly  12  with its sealing surface  13  is pressed against the closure plate  70 , and this in turn is pressed against the base of the second recess  22 . A fluid-tight seal is accordingly provided there. 
     The cover  80  is, by means of a circular cylindrical centering projection  56 , oriented transversely with respect to the axis of rotation  11 . In the direction of the axis of rotation  11 , said cover bears against a planar surface of the main body  20 . In the region of the receiving part  50 , the cover  80  is formed with a spacing to the receiving part  50 , such that the discussed movement clearance is realized. 
       FIG. 2  shows a perspective view of the inner part  41 , of the outer part  42  and of the drive shaft  30 . It is possible to see the external toothing  43  on the inner part  41  and the internal toothing  44  on the outer part  42 , which toothings mesh with one another. Opposite the toothing engagement, in each case at least one pair of teeth bear against one another in fluid-tight fashion, resulting in at least two pressure chambers which are delimited with respect to one another in fluid-tight fashion and the volume of which changes when the second shaft part  32  rotates. The second shaft part  32  is supported, rotatably with respect to the axis of rotation, on the main body and on the receiving part (numbers  22 ;  40  in  FIG. 1 ) by means of two slide rings  33  (see also  FIG. 3 ). It can also be seen how the cylindrical pin  55  engages into a recess on the outer circumference of the closure plate  70  in order to secure the latter against rotation. The outer circumferential surface  72  of the closure plate  70  is of circular cylindrical form with respect to the axis of rotation. With the separate holding plugs  73 , the closure plate  70  is oriented transversely with respect to the axis of rotation. Here, the holding plugs  73  engage into respectively associated bores in the closure plate  70  and in the receiving part  50 . The pump assembly preferably also comprises the closure plate  70 , wherein the latter can be installed as a whole into the main body. 
       FIG. 3  shows a further perspective view of the assembly as per  FIG. 2 . It can be seen that the holding plugs  73  project beyond the closure plate  70 , wherein said holding plugs bear against the base of the second recess (number  22  in  FIG. 1 ). Furthermore, it is possible to see the two kidney-shaped apertures  71  in the closure plate  70 , which apertures are arranged in the region of the toothing engagement between the inner and the outer part  41 ;  42 . One aperture  71  is connected to an associated fluid connection (number  21  in  FIG. 1 ), wherein the other aperture is connected at a suction side to the cylinder drum of the axial piston machine. 
       FIG. 4  shows a perspective view of the receiving part  50  from the side facing toward the main body. The outer circumferential surface  54  and the aperture  59  for the drive shaft are each of circular cylindrical form with respect to the axis of rotation  11 . The first recess  51  is likewise of circular cylindrical design, wherein it is arranged eccentrically and parallel with respect to the axis of rotation  11 . The end surface of the receiving part  50  is formed so as to be planar and perpendicular to the axis of rotation  11 , wherein two bores  57  for the cylindrical pin and two bores  58  for the holding plugs are arranged there. 
     Reference is also made to the kidney-shaped third recesses  53 , which are each arranged in alignment, in the direction of the axis of rotation  11 , with an associated aperture on the closure plate. The third recesses  53  have a planar base surface which is oriented perpendicular to the axis of rotation  11 . The depth of said third recesses is accordingly constant. 
       FIG. 5  shows a further perspective view of the receiving part  50 , from the side facing toward the cover. The centering projection  56  for the cover is of circular cylindrical form with respect to the axis of rotation  11 . Furthermore, in that surface of the receiving part  50  which is covered by the cover, there is provided a groove  52  for receiving the elastic element. The groove  52  runs in encircling, circular-ring-shaped fashion around the axis of rotation  11 , wherein said groove has a constant depth in the direction of the axis of rotation  11 . The groove is arranged as close as possible to the outer circumferential surface  54 , such that the elastic element can be designed to be particularly large. 
       FIG. 6  shows a perspective view of the elastic element  60 . The elastic element  60  is designed as a separate component in the form of an ondular washer. Said elastic element extends in circular-ring-shaped fashion around the axis of rotation  11 . In the circumferential direction, said elastic element has a discontinuity  62 , such that it is a slotted ring. This has a lower spring stiffness than a closed ring. The elastic element  60  is composed preferably of hardened spring steel. Along its circumference, it has a constant rectangular cross-sectional shape, wherein the relatively short rectangle side is arranged parallel to the axis of rotation  11 . In the circumferential direction, the elastic element  60  runs in undulating fashion, such that it bears against the base of the groove (number  52  in  FIG. 5 ) and against the cover (number  80  in  FIG. 1 ) only in each case at multiple contact regions  64  of small area. In the present case, on each side, four contact regions  64  are provided which are arranged in each case at an undulation trough or at an undulation peak. The stiffness of the elastic element is greater the shorter the wavelength or the more contact regions  64  are provided. A contact region  64  is divided by the discontinuity  62  into two parts, such that the two ring ends bear against the associated part there. The height  63  of the elastic element  60  in the direction of the axis of rotation  11 , reduced by the thickness of the cross-sectional shape in the direction of the axis of rotation  11 , corresponds to the maximum possible spring travel of the elastic element  60 . The preload of the elastic element is selected to be of such a magnitude that the hydrostatic forces occurring during operation are reliably exceeded. Consequently, no leaks occur at the sealing surface (number  13  in  FIG. 1 ). 
       FIG. 6  furthermore shows an undulation portion  61  which is defined by two directly adjacent contact points  64  on one side of the elastic element  60 . The stiffness of an undulation portion  61  may be calculated approximately analogously to the stiffness of a centrally loaded straight beam in bending, the length of which is equal to the circumferential length of the undulation portion  61 . A more accurate determination of the elasticity of the elastic element  60  is self-evidently possible by means of FEM calculation. 
     REFERENCE DESIGNATIONS 
     
         
           10  Connection assembly 
           11  Axis of rotation 
           12  Pump assembly 
           13  Sealing surface 
           20  Main body 
           21  Fluid connection 
           22  Second recess 
           30  Drive shaft 
           31  First shaft part 
           32  Second shaft part 
           33  Slide ring 
           40  Feed pump 
           41  Inner part 
           42  Outer part 
           43  External toothing of the inner part 
           44  Internal toothing of the outer part 
           50  Receiving part 
           51  First recess 
           52  Groove (for elastic element) 
           53  Third recess 
           54  Outer circumferential surface of the receiving part 
           55  Cylindrical pin 
           56  Centering projection 
           57  Bore for cylindrical pin 
           58  Bore for holding plug 
           59  Aperture for drive shaft 
           60  Elastic element 
           61  Undulation portion 
           62  Discontinuity 
           63  Height of the elastic element 
           64  Contact region 
           70  Closure plate 
           71  Aperture 
           72  Outer circumferential surface of the closure plate 
           73  Holding plug 
           80  Cover 
           81  Sealing ring