Patent Publication Number: US-2009238680-A1

Title: Pumping  unit

Description:
PRIOR ART 
     The invention is based on a pumping unit as generically defined by the preamble to the main claim. A pumping unit is already known from European Patent Disclosure EP 1 091 127 A1, with an impeller which is disposed in a pump chamber and is drivable to rotate by means of an actuator and has two face ends, diametrically opposite each of which is a respective end wall of the pump chamber, and a plurality of indentations for hydrodynamic support in both face ends of the impeller. A disadvantage is that dirt particles can collect in the indentations. If the dirt particles are flushed out of the indentations, they cause increased friction in the region between the annularly disposed indentations and hence cause scratches, since the axial gap there between the impeller and the pump chamber is smaller than the region of the indentations. 
     ADVANTAGES OF THE INVENTION 
     The pumping unit of the invention having the definitive characteristics of the body of the main claim has the advantage over the prior art that in a simple way, an improvement is obtained such that at least two adjacent indentations of the at least one face end and/or of the at least one end wall communicate with one another via a respective groove. In this way, the axial gap in the region between the indentations is increased in size, so that the dirt particles cannot cause increased friction and scratches there. 
     By the provisions recited in the dependent claims, advantageous refinements of and improvements to the pumping unit defined by the main claim are possible. 
     In an advantageous version, the indentations and grooves are disposed annularly and extend in arclike, split-ringlike, oblong slot-like or similar form. The indentations and the grooves are advantageously disposed on a common ring. 
     It is furthermore advantageous if the indentations have a greater depth than the grooves, since in this way oblique faces can be embodied that achieve a hydrodynamic support of the impeller. 
     It is especially advantageous that the indentations each have at least one face that is oblique with respect to the face ends and/or the end walls, for hydrodynamic support of the impeller, since in this way the axial position of the impeller is adjusted such that the two axial gaps between the impeller and the end walls of the pump chamber are at least nearly the same size. As a result, the friction acting on the impeller is reduced, and the efficiency of the pumping unit is increased. The at least one oblique face, when the indentations are disposed on the impeller, is each provided on a trailing end of the indentation relative to a direction of rotation of the impeller, and when the indentations are disposed on the end walls of the pump chamber, is each provided on a downstream end of the indentation. 
     It is also advantageous if the indentations each have a lowest point that extends parallel to the at least one face end and/or end wall. 
     It is moreover advantageous if the indentations of one face end of the impeller are diametrically opposite the indentations of the other face end of the impeller mirror-symmetrically relative to a middle face, and the indentations that are diametrically opposite mirror-symmetrically are joined together via a pressure equalization conduit. In this way it is attained that the pressure in the two indentations joined via the pressure equalization conduit is equalized. 
    
    
     
       DRAWINGS 
       Exemplary embodiments of the invention are shown in simplified form in the drawings and described in further detail in the ensuing description. 
         FIG. 1 , in section, shows a fragmentary view of the pumping unit of the invention; 
         FIG. 2  shows an impeller of the pumping unit; 
         FIG. 3  is a sectional view of the impeller taken along the line III-III in  FIG. 2 ; 
         FIG. 4  is a sectional view of the pumping unit taken along the line indentation-IV in  FIG. 1 ; 
         FIG. 5  is a sectional view of the pumping unit taken along the line V-V in  FIG. 1  in a second exemplary embodiment; and 
         FIG. 6  is a sectional view with the impeller and with indentations, disposed in an end wall of the pump chamber, in accordance with the second exemplary embodiment. 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
       FIG. 1  shows a pumping unit of the invention. 
     The pumping unit of the invention serves to pump a fluid, such as fuel, from a supply container to an internal combustion engine, for instance via a pressure line. 
     The pumping unit of the invention is embodied as a flow pump, such as a peripheral pump or lateral channel pump, and has a pump housing  1  which has a pump part  2  and a motor part  3 . 
     The pump part  2  has a pump chamber  4 , in which an impeller  5  revolves as it rotates about a rotationally symmetrical pump axis  8 . The impeller  5  is driven by an actuator  9 , provided in the motor part  3 , via a drive shaft  10 . The actuator  8  is an electric motor, for instance, and is disposed in a motor compartment  7  of the motor part  3 . 
     A region upstream of the pump chamber  4  is called the intake side, and a region downstream of the pump chamber  4  is called the compression side of the unit. 
     The pump chamber  4  has a pump chamber inlet  11  and a pump chamber outlet  12 . The pump chamber  4  is defined by two end walls diametrically opposite one another in the direction of the pump axis  8 , that is, a first end wall  15  and a second end wall  16 , the pump chamber inlet  11  being provided in the first end wall  15  and the pump chamber outlet  12  being provided in the second end wall  16 , and is defined in the radial direction relative to the pump axis  8  by an annular wall  17 . 
     The impeller  5  has a plurality of impeller blades  5 . 1 , and a blade chamber  5 . 2  is formed between blades. The blade chambers  5 . 2  are open toward the end walls  15 ,  16  and are closed radially outward for instance relative to the pump axis  8  by a ring  5 . 3 , which is disposed on the radially outer ends of the impeller blades  5 . 1 . However, the blade chambers  5 . 2  may expressly also be open radially outward and not have any ring  5 . 3 . 
     Annular feed conduits  14  are disposed in the end walls  15 ,  16 , in the radial region of the impeller blades  5 . 1 . 
     The first end wall  15  is part of an intake cap  18 , for instance, and the second end wall  16  and the annular wall  17  are for instance part of a pressure cap  19 . An inlet conduit  22  is provided in the intake cap  18  and discharges into the pump chamber  4  via the pump chamber inlet  11 ; the fluid pumped by the pumping unit leaves the pump chamber  4  via the pump chamber outlet  12 . The pump chamber  4  communicates fluidically with the motor compartment for instance via the pump chamber outlet  12  and an outlet conduit  23  that is provided in the pressure cap  19 . 
     The pressure cap  19  has a through opening  24 . The drive shaft  10 , mechanically coupled with the actuator  9 , begins at the motor compartment  7  and protrudes through the through opening  24  of the pressure cap  19  into the pump chamber  4 . 
     The axial width of the pump chamber  4  is greater than the axial width of the impeller  5 , so that one axial gap  20  each approximately ten to thirty micrometers wide exists between the impeller  5  and the respective end walls  15 ,  16 . The difference between the width of the pump chamber  4  and the width of the impeller  5  is defined as the total axial gap. 
     The impeller  5  is slipped for instance onto the drive shaft  10  protruding into the pump chamber  4 ; for this purpose, the impeller  5  has an impeller opening  25 , into which the drive shaft  10  at least protrudes so as to be connected to the impeller by positive and/or nonpositive engagement. The impeller  5  is supported on the drive shaft  10  for instance in such a way that it is movable axially between the first end wall  15  and the second end wall  16 . 
     The impeller  5  has a first face end  28 , which is oriented toward the first end wall  15  of the pump chamber  4 , and a second face end  29 , which is oriented toward the second end wall  16  of the pump chamber  4 . 
     In at least one of the face ends  28 ,  29  of the impeller  5  and/or at least one of the end walls  15 ,  16  of the pump chamber  4 , a plurality of indentations  38  are provided, for hydrodynamic support of the impeller  5 . In  FIG. 1 , the indentations  38  are disposed for instance on the face ends  28 ,  29  of impeller  5 . However, in a second exemplary embodiment, they may instead be provided on the end walls  15 ,  16  of the pump chamber  4 . The indentations  38  are embodied in such a way that they act like a hydrodynamic bearing and in this way adjust the axial position of the impeller  5  between the first end wall  15  and the second end wall  16  of the pump chamber in such a way that two equal-sized axial gaps  20  are created between the impeller  5  and the end walls  15 ,  16 . As a result, only slight forces of friction act on the impeller  5 , so that the efficiency of the pumping unit is improved. 
     The pumping unit aspirates fluid, for instance, from a supply container  32  via an inlet conduit  22 , the pump chamber inlet  11 , the pump chamber  4 , the pump chamber outlet  12 , the outlet conduit  23 , and the motor compartment  7  of the motor part of the pump housing  1 , and pumps the fluid, such as fuel, via a pressure line  33 , to an internal combustion engine  34 , for instance. In the pressure line  33 , a check valve  35 , for instance, is provided in order to maintain a predetermined pressure in the pressure line  33  after the pumping unit has been shut off. 
       FIG. 2  shows an impeller of the pumping unit with indentations in a first exemplary embodiment of the pumping unit of the invention. 
     In the impeller of  FIG. 2 , the elements that remain or function the same as in the pumping unit of  FIG. 1  are identified by the same reference numerals. 
     The indentations  38  are provided for instance radially inside the impeller blades  5 . 1  of the impeller  5  and are disposed located on an imaginary circular ring. The ring is provided centrally, for instance, relative to the pump axis  8 . By way of example, four indentations  38  are distributed uniformly over the circumference of the ring. However, it is expressly possible for an arbitrary number of indentations  38  to be provided. The indentations  38  extend for instance in arclike, split-ringlike, oblong slot-like or similar form. The indentations  38  each have one face  39  that is oblique relative to the face ends  28 ,  29  for the sake of hydrodynamically supporting the impeller  5 . The oblique face  39  for hydrodynamic support is disposed on a trailing end of the indentation  38 , with respect to a direction of rotation  31  of the impeller  5 . Each of the indentations  38  has a lowest point  40  that extends for instance parallel to the face ends  28 ,  29 . By way of example, the lowest point  40  of the indentations  38  is adjacent to two oblique faces  39 , one leading and the other trailing. In the first exemplary embodiment, the leading oblique face  39  has a shorter length, for instance a shorter arc length, than the oblique face  39  that is trailing in the direction of rotation. The oblique face  38  leading in the direction of rotation may also be omitted and replaced with a steplike shoulder, since it makes no contribution to the hydrodynamic support. 
     According to the invention, at least two adjacent indentations  38  of the at least one face end  28 ,  29  and/or of the at least one end wall  15 ,  16  communicate with one another via a respective groove  42 . In the first exemplary embodiment, both face ends  28 ,  29  of the impeller  5  are provided with indentations  38 . For example, each indentation  38  communicates with the respective adjacent indentation  38  via a groove  42 . The grooves  42  extend for instance in arclike, ringlike or similar for, so that the indentations  38  and the grooves  42  together form one common ring. The indentations  38  and grooves  42 , however, remain different at least in the respect that the depth of the grooves  42  is less than the depth of the lowest point  40  and of the oblique faces  39  of the indentations  38  ( FIG. 3 ). The width Bn of the grooves  42 , measured in the radial direction with respect to the pump axis  8 , is for example equal to the width Bv, measured radially with respect to the pump axis  8 , of the indentations  38 , but may also be different. 
     The oblique faces  39  of the indentations  38  are formed by the provision that the pressure equalization conduits of the indentations  38 , beginning from the lowest point  40  of each, to the adjacent groove  42  decreases, for instance continuously. 
       FIG. 3  shows a sectional view of the impeller taken along the line III-III in  FIG. 2 . 
     In the region of the lowest point  40 , the indentations  38  extend for instance approximately parallel to the face ends  28 ,  29 . After that, viewed counter to the direction of rotation  41 , they extend along a trailing oblique face  39 , with a reduction in the depth, in the direction of a trailing groove  42  in terms of the direction of rotation  41  and discharge into this groove. Viewed in the direction of rotation, the depth of the indentation  38  decreases, either via a steplike shoulder  43  shown in dashed lines or via a leading oblique face  39  and discharges into a leading groove  42 . 
     The indentations  38  of one face end  28  of the impeller  5  are diametrically opposite the indentations  38  of the other face end  29  of the impeller  5 , for instance mirror-symmetrically relative to a middle face  45 , and the indentations  38  diametrically opposite one another mirror-symmetrically communicate with one another via a pressure equalization conduit  46 . In this way, an equally high pressure builds in both of the indentations  38  that communicate via the pressure equalization conduit  46 . The pressure equalization conduit  46  discharges into the indentation  38  for instance in each case in the region of the lowest point  40 . 
     The fluid located in the axial gap  20  is entrained in the direction of rotation  41  upon the rotation of the impeller  5  and has a relative speed oriented counter to the direction of rotation  41  with respect to the impeller  5 . The fluid in the axial gap  20  therefore flows through the indentations  38  and the grooves  42  counter to the direction of rotation  41 . In the region of the trailing oblique face  39 , the flow cross section narrows in wedgelike form between the face ends  28 ,  29  of the impeller  5  and the end walls  15 ,  16  of the pump chamber  4 , so that an increasingly higher pressure in the fluid builds up and acts on the respective face end  28 ,  29  of the impeller  5  and in this way adjusts the axial position of the impeller  5  in such a way that axial gaps  20  of equal size result. 
       FIG. 4  is a sectional view of the pumping unit taken along the line indentation-IV in  FIG. 1  and  FIG. 5  is a sectional view of the pumping unit taken along the line V-V in  FIG. 1  in a second exemplary embodiment. 
     In the pumping unit of  FIG. 4  and  FIG. 5 , the elements that remain the same or function the same as in the pumping unit of  FIGS. 1 through 3  are identified by the same reference numerals. 
     The second exemplary embodiment of  FIG. 4  differs from the first exemplary embodiment of  FIGS. 1 through 3  in that the indentations  38  are disposed not on the two face ends  28 ,  29  of the impeller  5  but rather on the two end walls  15 ,  16  of the pump chamber  4 . The pressure equalization conduits  46  are omitted. The indentations  38 , when disposed on the end walls  15 ,  16  of the pump chamber  4  in contrast to the disposition on the impeller  5 , experience a flow through them in the direction of rotation of the impeller  5 . The oblique faces  39  for hydrodynamic support should therefore each be disposed on one downstream end, in terms of the flow direction in the axial gap  20 , of the indentation  38 . 
     In the second exemplary embodiment, the indentations  38  are disposed radially inside the feed conduit  14  with respect to the pump axis  8 . In the region of the lowest point  40 , the indentations  38  extend for instance at least approximately parallel to the end walls  15 ,  16 . Downstream, they extend via a rear oblique face  39 , in terms of the flow direction in the axial gap  20 , for hydrodynamic support with a reduction in depth, as far as a downstream groove  42  and discharge into it. Upstream, the depth of the indentation  38  decreases, either via a steplike shoulder  43  or via an upstream oblique face  39  and discharges into a groove  42  located upstream in terms of the flow direction. 
     The indentations  38  of the one end wall  15  of the pump chamber  4  are diametrically opposite the indentations  38  of the other end wall  16  of the pump chamber  4 , for instance mirror-symmetrically relative to a middle face that is located in the middle between the end walls  15 ,  16  and extends parallel to them. 
       FIG. 6  is a sectional view with the impeller and with indentations, disposed in an end wall of the pump chamber, in accordance with the second exemplary embodiment. 
     In the pumping unit of  FIG. 6 , the elements that remain the same or function the same as in the pumping unit of  FIGS. 1 through 5  are identified by the same reference numerals.