Abstract:
The invention relates to a pump module ( 2 ) comprising a housing part ( 4 ) with precisely determined force introduction points ( 25 ) in relation to adjacent components. Supporting elements ( 24, 27 ) and a groove ( 26 ) are located between the force introduction points ( 25 ) and a disc element ( 20 ) that comprises a partially annular channel ( 10 ). Forces that are introduced into the housing parts ( 4 ) thus lead to negligible deformations in the areas of said housing parts ( 4 ) that are adjacent to the impeller.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to a fuel pump with a pump stage driven by an electric motor, with a jacket surrounding the electric motor and the pump stage and having an impeller arranged rotatably between two casing parts of the pump stage, with an inlet duct arranged in one of the casing parts and an outlet duct arranged in the opposite casing part, with rings, arranged in the impeller, of guide blades delimiting blade chambers, and with part-annular ducts arranged in the casing parts and located opposite the rings of the guide blades, the part-annular duct of the inlet-side casing part being connected to the inlet duct and the part-annular duct of the outlet-side casing part being connected to the outlet duct.  
         [0002]     Such fuel pumps are often used for the conveyance of fuel out of a fuel tank to an internal combustion engine in present-day motor vehicles and are known from practice. The casing parts of the known pump stages are manufactured mostly from metal or sintered ceramic, in order to achieve an intended stability. For example, as a result of holding forces of the jacket or owing to temperature fluctuations, forces are introduced into the pump stage, which lead to a flexion of the casing parts. Furthermore, a return body is supported over the entire circumference on one of the casing parts of the pump stage and is braced radially with respect to the casing part. Both axial and radial forces are therefore introduced into the casing part, thus likewise leading to a flexion of the casing part. However, a flexion of the casing parts leads to a variation in an axial gap between the casing parts and the impeller. Moreover, a pressure generated by the pump stage in the electric motor leads to a reduction in the axial gap between the casing part arranged nearest to the electric motor and the impeller.  
         [0003]     The known fuel pump has the disadvantage that it is highly cost-intensive to produce because the casing parts of the pump stage are manufactured from metal or sintered ceramic.  
         [0004]     The problem on which the invention is based is to design a fuel pump of the type initially mentioned, in such a way that it can be produced particularly cost-effectively and a flexion of the casing parts of the pump stage is largely avoided.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0005]     This problem is solved, according to the invention, in that the casing parts have a disk element with one of the part-annular ducts, and in that they have, on the outer circumference of the disk element, connecting elements with force introduction surfaces for connection to adjoining components of the jacket or of the electric motor, and in that the connecting elements are arranged in the region of the neutral fiber in terms of the buckling of the casing parts, or in that supporting elements are provided which are designed for the reversal of forces introduced into the casing parts at the force introduction points and consequently for the generation of counterforces corresponding to the introduced forces.  
         [0006]     By virtue of this configuration, a lever arm between the force introduction points and the radially inner region of the casing parts which is formed by the disk element is avoided. The connecting elements lead to an exactly determinable point at which the forces are introduced into the casing parts. Forces introduced from adjoining components into the casing parts therefore no longer lead to a flexion of the casing parts in their regions adjoining the impeller.  
         [0007]     Owing to the invention, the casing parts can be manufactured from particularly cost-effective materials.  
         [0008]     According to an advantageous development of the invention, the introduction of the forces into the neutral fiber in terms of buckling requires a particularly low structural outlay when the connecting elements have a rim arranged on the outer circumference of the disk element.  
         [0009]     According to another advantageous development of the invention, a flexion of the inlet-side casing part by radial forces introduced into the pump stage through the jacket can be avoided in a simple way when the rim is arranged at half the height of the disk element of the inlet-side casing part having essentially a uniform thickness.  
         [0010]     According to another advantageous development of the invention, a flexion of the outlet-side casing part as a result of axial forces of adjoining components can be avoided in a simple way when the rim is arranged vertically on the outer circumference of the disk element of the outlet-side casing part and has a collar projecting radially outward, and when the force introduction points for axially introduced forces are arranged on the collar.  
         [0011]     According to another advantageous development of the invention, the connection of the regions of the outlet-side casing part which are located opposite the impeller to the force introduction points can transmit only very low forces when the outlet-side casing part has a groove between the rim and the radially inner region of the disk element.  
         [0012]     According to another advantageous development of the invention, the outlet-side casing part has particularly high stability when radially inner supporting elements interrupt the groove and connect the disk element to the rim.  
         [0013]     The rim of the outlet-side casing part can flex during the introduction of axial forces, without forces being introduced into that region of the disk element which is located opposite the impeller, when the rim is spaced apart from the radially outer boundary of the outlet-side casing part.  
         [0014]     According to another advantageous development of the invention, a contribution is made to a further reduction in the moments of flexion introduced into the disk element when radially outer supporting elements are arranged, offset with respect to the radially inner supporting elements, on the radially outer side of the rim.  
         [0015]     In the case of forces introduced axially into the outlet-side casing part, the rim can undergo deformation virtually independently of the disk element when the force introduction points for axially introduced forces are arranged on the radially outer supporting elements. This contributes to a further reduction in the moments of flexion introduced into the disk element.  
         [0016]     According to another advantageous development of the invention, an introduction of radial forces into the outlet-side casing part over the entire circumference can be avoided in a simple way when individual force introduction points for radially introduced forces are arranged on the rim.  
         [0017]     According to another advantageous development of the invention, a thermal deformation of the disk element of the outlet-side casing part due to waste heat from the electric motor can be avoided in a simple way when the outlet-side casing part has an annular recess between the part-annular duct and a mounting of the shaft.  
         [0018]     The fuel pump according to the invention can be manufactured particularly cost-effectively when at least one of the casing parts is manufactured from plastic. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The invention permits numerous embodiments. To make its basic principle even clearer, one of these is illustrated in the drawing and is described below. In the drawing:  
         [0020]      FIG. 1  shows a longitudinal section through a fuel pump according to the invention.  
         [0021]      FIG. 2  shows a top view of an outlet-side casing part of the fuel pump from  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]      FIG. 1  shows a longitudinal section through a fuel pump with a pump stage  2  driven by an electric motor  1  and designed as a side channel pump. The pump stage  2  has an impeller arranged rotatably between two casing parts  3 ,  4 . The impeller  5  is arranged fixedly in terms of rotation on a shaft  6  of the electric motor  1  and has two rings, located opposite one another, of guide blades  8  delimiting blade chambers  7 . Part-annular ducts  9 ,  10  are arranged in each case, opposite the rings of the guide blades  8 , in the casing parts  3 ,  4 . The part-annular ducts  9 ,  10  form with the blade chambers  7  a conveying chamber  13  leading from an inlet duct  11  to an outlet duct  12 . The inlet duct  11  and the outlet duct  12  are arranged on casing parts  3 ,  4  located opposite one another. The casing parts  3 ,  4  are spaced apart by means of a ring  14 . Furthermore, the fuel pump has a jacket  15  made from sheet metal.  
         [0023]     The jacket  15  is flanged at its ends and prestresses the components of the fuel pump with respect to one another. The inlet-side casing part  3  consists essentially of a planar disk element  16  and of a rim  17  arranged at half the height of its circumference. The rim  17  is consequently arranged level with the neutral fiber in terms of the buckling of the inlet-side casing part  3  and forms a force introduction point  18  for the jacket  15 . A flanging  19  of the jacket  15  engages behind the rim  17 . Radial forces introduced from the flanging  19  into the rim  17  consequently do not lead to a flexion of the inlet-side casing part  3 .  
         [0024]     The outlet-side casing part  4  has a disk element  20  located opposite the impeller  5  and, near its outer circumference, a rim  21  arranged perpendicularly with respect to the disk element  20  and in  FIG. 2  is illustrated in a top view from the side of the electric motor  1  of  FIG. 1 . A collar  22  running around radially outside the rim  21  is led as far as the jacket  15 . A return ring  23  of the electric motor  1  is supported axially on radially outer supporting elements  24  of the pump stage  2  which are arranged on the collar  22 . Force introduction points  25  for forces introduced axially into the outlet-side casing part  4  are consequently arranged on the radially outer supporting elements  24 . Force introduction points  25 ′ for forces introduced radially into the outlet-side casing part  4  are arranged on the rim near to the radially outer supporting elements  24  only. The outlet-side casing part  4  has, as seen radially on the inside from the rim  21 , a groove  26  which is interrupted by radially inner supporting elements  27  connecting the rim  21  to the disk element  20 . The radially inner supporting elements  27  are arranged so as to be offset with respect to the radially outer supporting elements  24 . Axial forces from the return ring  23  of the electric motor  1  are introduced into the outlet-side casing part  4  via the radially outer supporting elements  24  and may lead to a deformation of the rim  21 . A transmission of the forces to the disk element  20  is avoided by the arrangement of the radially inner and outer supporting elements  24 ,  27  and the groove  26  in relation to one another. When the return ring  23  of the electric motor  1  exerts a radial prestress on the outlet-side casing part, the forces can be introduced only at the force introduction points  25 ′ for the radial forces. Owing to the offset of the radially inner supporting elements  27  having the force introduction points  25 ′ for the radial forces, a countermoment is generated at the disk element  20  and prevents the flexion of the latter.  
         [0025]     The outlet-side casing part  3  has an annular recess  28  in its radially inner region, as seen from the part-annular duct  10 . This annular recess  28  decouples that region of the outlet-side casing part  4  which is located opposite the shaft  6  of the electric motor  1  from the region having the part-annular duct  10 . Moreover, the outlet-side casing part  4  has a mounting  29  for the shaft  6  of the electric motor  1 .  
         [0026]     In an alternative embodiment, not illustrated, the return ring  23  of the electric motor  1  may also have individual supporting elements, by means of which it is supported between the radially inner supporting elements  27  of the outlet-side casing part  4 . In this case, the force introduction points would be arranged directly on the collar  22  running around.