Abstract:
The invention relates to a feed pump ( 2 ) that is configured as a side-channel pump with a plurality of identically designed feed chambers ( 6, 7 ) with outlet channels ( 22, 23 ) that are disposed opposite one another, thereby eliminating the radial forces acting upon the impeller ( 4 ) of the feed pump ( 2 ). The feed pump ( 2 ) according to the invention is especially wear-free and has a very high degree of efficiency.

Description:
CLAIM FOR PRIORITY 
   This application claims priority to International Application No. PCT/DE01/04675, which was published in the German language on Jun. 20, 2002, which claims the benefit of priority to German Application No. 10062451.0 which was filed in the German language on Dec. 14, 2000. 

   TECHNICAL FIELD OF THE INVENTION 
   The invention relates to a feed pump with a driven impeller which rotates in a pump casing and which has in its end faces at least one ring of guide vanes delimiting vane chambers, and with at least one part-annular channel which is arranged in the region of the guide vanes in the pump casing and which forms, with the vane chambers, a feed chamber from an inlet duct to an outlet duct. 
   BACKGROUND OF THE INVENTION 
   Such feed pumps are often used, for example in present-day motor vehicles, for feeding fuel or windshield cleaning fluid and are known from practice. The impeller of the feed pump is fastened on a shaft of an electric motor. The feed pump has as an axial bearing, in a radially inner region of the impeller, as seen from the vane chambers, interconnected pockets for collecting the fluid to be fed by the pump. These pockets form, with the fluid, an axial plain bearing. 
   One disadvantage of the known feed pump is that the impeller and consequently the shaft driving the impeller are subjected to very high load in the radial direction, since the pressure within the feed chamber is substantially higher in the region of the outlet duct than in the -region of the inlet duct. This leads to very high friction in bearings of the impeller. Moreover, the friction reduces the efficiency of the feed pump. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to configure a feed pump of the type initially mentioned, in such a way that it has as high efficiency as possible. 
   According to an aspect of the invention, a plurality of feed chambers, of which the outlet ducts and inlet ducts are arranged in each case symmetrically about the axis of rotation of the impeller, is provided. 
   By virtue of this configuration, the forces transmitted to the impeller by the fluid flowing in the feed chambers have, in the radial direction, directions of force which are opposite to one another. The forces consequently cancel one another, so that bearing forces of the shaft driving the impeller can be kept particularly low. The feed pump according to this aspect of the invention therefore has particularly high efficiency. A further advantage of this configuration of the feed pump according to this aspect of the invention is that it has very low wear and therefore has a particularly long useful life. 
   According to this aspect of the invention, the feed pump may have a multiplicity of feed chambers if the feed chambers in each case extend over a fraction of their circle diameter. 
   The feed chambers of the feed pump according to this aspect of the invention extend over virtually their entire circle diameter when the feed chambers are arranged on opposite end faces of the impeller. As a result, the feed pump has particularly high efficiency. 
   According to another aspect of the invention, axial forces can be distributed uniformly over one side of the impeller when vane chambers arranged on the two end faces of the impeller overlap and when the inlet ducts of the feed chambers are arranged on one end face of the impeller and the outlet ducts on the other end face of the impeller. The axial forces acting on the impeller can thereby be supported in a simple way. Furthermore, as a result of this configuration, the feed pump according to the invention has the flow passing through it axially and can therefore be arranged in a particularly space-saving way, for example, in a feed unit for fuel in a motor vehicle. 
   According to another advantageous development of the invention, a mounting of the impeller is configured in a particularly simple way in structural terms when a radial bearing is arranged between the impeller and an electric motor driving the impeller and an axial bearing is arranged on that side of the impeller which is located opposite the radial bearing. 
   According to another aspect of the invention, the axial bearing is constructed in a particularly simple way and can therefore be manufactured particularly cost-effectively when the axial bearing has a ball provided for supporting a shaft driving the impeller. 
   The feed pump according to the invention has particularly low flow losses and consequently very high efficiency when the outlet ducts and/or the inlet ducts are arranged so as to point in the radial direction toward the feed chambers. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a feed pump according to the invention in longitudinal section, 
       FIG. 2  shows the feed pump from  FIG. 1  in sectional illustration along a line II—II, 
       FIG. 3  shows a further embodiment of the feed pump according to the invention in longitudinal section, and 
       FIG. 4  shows the feed pump from  FIG. 3  in sectional illustration along a line IV—IV. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a feed pump  2  driven by an electric motor  1  and having an impeller  4  rotating in a pump casing  3 . The feed pump  2  is designed as a side-channel pump and can be used, for example, for the feed of fuel or windshield washing fluid in a motor vehicle. The impeller  4  is fastened on a shaft  5  of the electric motor  1 . The feed pump  2  has two feed chambers  6 ,  7  separate from one another. The feed chambers  6 ,  7  have in each case a part-annular channel  8 ,  9  arranged in the pump casing  3  and vane chambers  12 ,  13  delimited by guide vanes  10 ,  11  of the impeller  4 . The shaft  5  has, near the electric motor  1 , a radial bearing  14  and, below the impeller  4 , an axial bearing  15  with a ball  16  arranged in the pump casing  3 . The ball  16 , like the shaft  5 , is hardened. Pockets  18 ,  19  connected to one another via ducts  17  are worked in the end faces of the impeller  4 . The pockets  18 ,  19  are filled by the leakage of the fluid to be fed and, with the opposite wall of the pump casing  3 , form axial plain bearings. 
   As  FIG. 2  shows in a cross section through the feed pump  2  from  FIG. 1  along the line II-II, the feed chambers  6 ,  7  have in each case an inlet duct  20 ,  21  and an outlet duct  22 ,  23 . 
   The inlet ducts  20 ,  21  issue in each case into the start of the part-annular channels  8 ,  9 . The outlet ducts  22 ,  23  are arranged at the ends of the part-annular channels  8 ,  9  in the direction of flow of the fluid to be fed. For illustration, the direction of rotation of the impeller  4  and the directions of flow in the inlet ducts  20 ,  21  and the outlet ducts  22 ,  23  are identified by arrows. During a rotation of the impeller  4 , the guide vanes  10 ,  11  generate circulating flows in the feed chambers  6 ,  7  and feed the fluid from the inlet ducts  20 ,  21  to the outlet ducts  22 ,  23 . The inlet ducts  20 ,  21  and the outlet ducts  22 ,  23  are in each case arranged opposite one another. Since a higher pressure prevails in the feed chambers  6 ,  7  near the outlet ducts  22 ,  23  than at the inlet ducts  20 ,  21 , the radial forces acting on the impeller  4  cancel one another as a result of this configuration. 
   Furthermore,  FIGS. 1 and 2  show that the inlet ducts  20 ,  21  and the outlet ducts  22 ,  23  are arranged so as to point in the radial direction toward the feed chambers  6 ,  7 . 
     FIG. 3  shows a feed pump  25  driven by an electric motor  24  and having feed chambers  27 ,  28  passing through an impeller  26 . For this purpose, vane chambers  29 ,  30  arranged in the impeller  26  and located opposite one another are connected to one another. On its side facing away from the electric motor  24 , the feed pump  25  has two inlet ducts  31 ,  32  issuing from radially outside into a feed chamber  27 ,  28  in each case.  FIG. 4  shows, in a cross section through the feed pump  25  from  FIG. 3  along the line IV—IV, that the feed chambers  27 ,  28  extend over a fraction of their circle diameter. The feed chambers  27 ,  28  have in each case an outlet duct  33 ,  34  led slightly radially outward. The outlet ducts  33 ,  34  and consequently also the inlet ducts  31 ,  32  are arranged opposite one another, so that radial forces acting on the impeller  26  cancel one another.  FIG. 3  shows, for example at one of the outlet ducts  33 , that the outlet ducts  33 ,  34  pass through a pump casing  35  in the direction of the electric motor  24 . This feed pump  25  is designed as a side-channel pump. The feed pump  25  may, of course, also be configured as a peripheral pump with vane chambers arranged in the outer circumference.