Patent Document

BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention is directed to an improved fuel delivery system for delivering fuel to an internal combustion engine of a motor vehicle. 
   2. Description of the Prior Art 
   A fuel delivery system with a pump chamber and a revolving impeller in the pump chamber rotating about a pump axis is already known from German Patent Disclosure DE 32 26 325 A1 in which protuberances are provided on predetermined end walls inside the pump chamber. The protuberances are disposed radially inward from a pump conduit provided in the end wall, and they extend away from the pump conduit in a straight line, rising in wedgelike fashion in the direction of revolution. In the rotation of the impeller in the pump chamber, the fluid backs up at the protuberances, generating a resultant force in the axial direction, pointing away from the end wall, and preventing the impeller from being able to come to rest on one of the end walls of the pump chamber. As a result, the protuberances act like a hydrodynamic bearing. Because of this, the friction acting counter to the impeller rotating in the pump chamber is reduced, and the efficiency of the fuel pump is increased. A disadvantage is that the protuberances are very complicated to produce. 
   OBJECT AND SUMMARY OF THE INVENTION 
   The delivery system of the invention has the advantage over the prior art that increasing the efficiency of the delivery system is attained in a simple way by means of reducing the friction acting on the impeller; this is done by disposing the protuberances in at least one ring around the pump axis. The protuberances space the impeller apart from the end walls of the pump chamber and are very simple and economical to produce. 
   Advantageous refinements of the improved delivery system of the invention are possible. It is especially advantageous if the protuberances are provided on a first end wall of an intake cap and/or on a second end wall of a pressure cap, because the protuberances on the end walls of the intake cap or the pressure cap are especially simple to make. 
   It is equally advantageous if the protuberances are disposed on the impeller, since the protuberances on the impeller are also very simple and economical to make. 
   It is highly advantageous if the height of the protuberances amounts to approximately half the difference between the axial width of the pump chamber and the axial width of the impeller, because in this way the friction acting on the impeller can be still further reduced. Moreover, a leakage flow from a higher-pressure region along the axial gap back into a lower-pressure region of the pump chamber is advantageously reduced. 
   In an advantageous feature, the width of the protuberances, measured in the radial direction, is about 0.8 mm. In this way, the contact area upon contact of the impeller and protuberances is small. 
   In another advantageous feature, the protuberances are embodied as square, rectangular, circular-annular, crescent-shaped, trapezoidal, or lenticular. 
   It is furthermore advantageous if the protuberances are rounded on a top side oriented toward the pump chamber, since in this way the contact area on which the impeller could come to rest is reduced. 
   In an advantageous exemplary embodiment, the number of protuberances disposed on a ring is in the range between 3 and 20. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawings, in which: 
       FIG. 1  in section shows a fragmentary view of the delivery system of the invention; 
       FIG. 2  is a sectional view through a first exemplary embodiment taken along the line II—II in  FIG. 1 ; 
       FIG. 3  is a sectional view of the first exemplary embodiment taken along the line III—III in  FIG. 2 ; 
       FIG. 4  is a sectional view of a second exemplary embodiment taken along the line IV—IV in  FIG. 1 ; 
       FIG. 5  is a sectional view of the second exemplary embodiment taken along the line V—V in  FIG. 1 , and 
       FIG. 6  is a fragmentary sectional view taken along line VI—VI of  FIG. 5 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a delivery system of the invention which serves to pump a fluid, such as fuel, from a supply container, for instance via a pressure line, to an internal combustion engine. 
   The delivery system embodied according to the invention has a pump housing  1 , which has a pump part  2  and a motor part  3 . 
   The system of the invention may be a positive displacement pump, such as a roller cell pump or geared pump, or a flow pump, such as a peripheral pump or side channel pump. 
   A roller cell pump is known for instance from German Patent Disclosure DE 44 37 377 A1, which is hereby expressly incorporated herein by reference. A flow pump is known for instance from German Patent Disclosure DE 44 35 883 A1, which is also hereby expressly incorporated herein by reference. 
   The pump part  2  has a pump chamber  4 , in which an impeller  5  revolves, rotating about a rotationally symmetrical pump axis  8 . The impeller  5  may be a well-known impeller of a flow pump, or a rotor that has rollers in a roller cell pump. The rollers of the roller cell pump are provided in rotor slots disposed on the circumference. 
   The impeller  5  is driven by an actuator  9 , provided in the motor part  3 , via a drive shaft  10 . The actuator is an electric motor, for instance, and is disposed in a motor chamber  7  of the motor part  3 . 
   A region upstream of the pump chamber  4  is known as the intake side, and a region downstream of the pump chamber  4  is known as the compression side of the system. 
   The pump chamber  4  has a pump chamber inlet  11  and a pump chamber outlet  12 . The pump chamber  4  is defined by two opposed end walls in the direction of the pump axis  8 , that is, a first end wall  15  and a second end wall  16 , where the pump chamber inlet  11  is provided in the first end wall  15  and the pump chamber outlet  12  is 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 . 
   In  FIG. 1 , a side channel pump is shown as an example, with an impeller  5  that has impeller blades  5 . 1 , and with annular delivery conduits  14 , which are provided in the end walls  15 ,  16  and are disposed 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 pump chamber  4  communicates fluidically with the motor chamber  7  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 chamber  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 there is an axial gap  20  approximately ten to thirty micrometers wide between the impeller  5  and the 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  that protrudes 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 joined by positive and/or nonpositive engagement to the impeller. The impeller  5  is supported on the drive shaft  10  in such a way for instance that it is axially movable between the first end wall  15  and the second end wall  16 . 
   The delivery system aspirates fluid, for instance, from a supply container  32  via the inlet conduit  22 , the pump chamber inlet  11 , the pump chamber  4 , the pump chamber outlet  12 , the outlet conduit  23 , and the motor chamber  7  of the motor part of the pump housing  1 , and delivers the fluid, such as fuel, to an internal combustion engine  34 , for instance, via a pressure line  33 . In the pressure line  33 , a check valve  35  is for instance provided, so as to maintain a predetermined pressure in the pressure line  33  after the delivery system has been shut off. 
     FIG. 2  in section shows a sectional view of a first exemplary embodiment of the system of the invention taken along the line II—II in  FIG. 1 . In this system, those parts that remain the same or function the same as in the system of  FIG. 1  are identified by the same reference numerals. 
   On the first end wall  15  of the intake cap  18  and/or on the second end wall  16  of the pressure cap  19 , protuberances  28  are provided, which are raised relative to the main surface of the end wall  15 ,  16 . However, the protuberances may also be disposed on one or both end faces  21  of the impeller  5  that are oriented toward the end walls  15 ,  16 . 
   The radial position of the protuberances  28  can be selected arbitrarily, as long as they are not located in the radial region of the delivery conduit and/or of the blades of the impeller of a flow pump or of the slots and rollers of a roller cell pump. For instance, the protuberances  28  are located on a radius that is less than the radius of the side channel and the blades of the impeller of a side channel pump, or less than the radius of the guidance of the rollers in the rotor of a roller cell pump. The operative moments of friction at the impeller  5  are all the less, the farther radially inward the protuberances  28  are disposed. 
   According to the invention, the protuberances  28  are disposed in at least one imaginary ring  29  around the pump axis  8  and are spaced apart from one another circumferentially and radially. The protuberances  28  are distributed uniformly along the imaginary ring  29 , for instance. The protuberances  28  are for instance square, rectangular, circular-annular, crescent-shaped, trapezoidal, oval, cylindrical, or lenticular. The cross sectional shape and the end face of the protuberances  28 , however, are expressly arbitrary and may be embodied differently in the various different protuberances  28 . For instance, the end face of the protuberances  28  is small compared to the end walls  15 ,  16  of the pump chamber  4  and to the end faces  21  of the impeller  5 . 
   Because of the protuberances  28 , there is a predetermined minimum spacing between the impeller  5  and an end wall  15 ,  16 . In this way, the friction which is set counter to the impeller  5  by the fluid, pumped by the system, in the rotation in the pump chamber  4  is reduced. The protuberances  28  prevent the axial gap  20  between the impeller  5  and one of the end walls  15 ,  16  from becoming too large, as a result of axial displacement of the impeller  5  on the drive shaft  10 , so that an excessively great leakage flow from a higher-pressure region along the axial gap  20  back into a lower-pressure region of the pump chamber  4  will not occur. The magnitude of the leakage flow is dependent on the cube of the width of the axial gap  20 , so that the width of the axial gap  20  has very major effects on the leakage flow and hence on the efficiency of the delivery system. 
   By means of the protuberances  28 , a considerable increase in efficiency of the pump part  2  and thus of the system can be attained, since both friction and the leakage flow are reduced. 
   The impeller  5  is oriented by means of the protuberances  28  such that two defined axial gaps  20  are embodied. 
   Preferably, a height  28 . 1  of the protuberances  28 , measured in the axial direction, is selected such that the axial gap  20  between the impeller  5  and the first end wall  15  and the axial gap  20  between the impeller  5  and the second end wall  16  are each the same size and each amount to approximately half the total axial gap. In this way, the impeller is oriented and supported in the axial center of the pump chamber  4 . However, the axial gaps  20  may expressly also be of different sizes. 
   The height  28 . 1  of the protuberances  28  is for instance about eight micrometers, but can expressly be selected arbitrarily and may also differ for different protuberances. The number of protuberances  28  disposed on a ring  29  is for instance in a range between three and twenty and is preferably seven. The width of the protuberances  28  measured in the radial direction is for instance about 0.8 mm, but can likewise be designed arbitrarily. 
   The protuberances  28  are disposed on a radius that is shorter than or greater than the radius on which the delivery conduit  14  is provided. 
   Between the individual protuberances  28 , one or more recesses or grooves  27  each may be provided. 
   The protuberances  28  are fabricated for instance such that in a first production step, at least one annular shoulder is turned; it corresponds to the ring and is raised relative to the main surface of the end wall  15 ,  16 . The annular shoulder  29  is interrupted in a second production step by the recesses or grooves  27 , in such a way as to create a plurality of individual protuberances  28 , which are spaced apart from one another, for instance uniformly, and distributed over the ring  29 . Preferably, the first production step and the second production step are transposed, and the recesses or grooves are embodied for instance as crescent-shaped or circular-annular grooves  27  and distributed, for instance uniformly, over a ring  29 . The sides of the protuberances  28  oriented toward the grooves  27  are for instance curved circularly inward. 
   In a disposition of the protuberances  28  on the end wall  15 ,  16  of the pump chamber  4 , the recesses or grooves  27  may begin at the top  30  of the protuberances  28  and extend past the end wall  15 ,  16  into the intake cap  18  or the pressure cap  19 , and in the case of a disposition of the protuberances  28  on the impeller  5 , they can extend past the end faces  21  of the impeller  5  on into the impeller  5 . In this way, the recesses or grooves  27  are embodied as indentations. As an example, one such indentation is shown in  FIG. 2  between two protuberances  28 ; it is understood that it may also be provided between the other protuberances  28  as well. 
   In this way, the protuberances  28  form a crown-shaped shoulder, which can also be called a running crown, with protuberances  28  as the upward-protruding parts of the crown and indentations or recesses  27  between the protuberances  28 . 
   It is understood that the protuberances  28  may be fabricated in some other way instead. 
     FIG. 3  in section shows a fragmentary view of the first exemplary embodiment taken along the line III—III in  FIG. 2 , with an impeller shown in shaded fashion. 
   In the system of  FIG. 3 , those parts that remain the same or function the same as in the systems of  FIGS. 1 and 2  are identified by the same reference numerals. 
   The protuberances  28  are for instance rounded on a top  30  oriented toward the pump chamber  4 , in order to reduce the contact area on which the impeller  5  could come to rest. 
     FIG. 4  in section shows a fragmentary view of the first exemplary embodiment taken along the line IV—IV in  FIG. 2 , with an impeller shown in shaded fashion. 
   In the system of  FIG. 4 , those parts that remain the same or function the same as in the systems of  FIGS. 1–3  are identified by the same reference numerals. 
   In this version, the recesses or grooves  27  extend for instance on into the intake cap  18 . They are embodied as wider in the radial direction, for instance, than the protuberances  28 . 
     FIG. 5  in section shows a fragmentary view of the first exemplary embodiment taken along the line V—V in  FIG. 1 . 
   In the system of  FIG. 5 , those parts that remain the same or function the same as in the systems of  FIGS. 1–4  are identified by the same reference numerals. 
   The system of  FIG. 5  differs from the system of  FIG. 2  in the fact that the protuberances are embodied as lenticular. 
   The diameter of the lenticular protuberances  28  disposed on a ring  29  is arbitrary. 
   The lenticular protuberances  28  are molded integrally onto the end walls  15 ,  16  of the pump chamber  4  or onto the end faces  21  of the impeller  5 , for instance, by means of injection molding. 
     FIG. 6  in section shows a fragmentary view of the first exemplary embodiment taken along the line VI—VI in  FIG. 5 , with an impeller shown in shaded fashion. 
   In the system of  FIG. 6 , those parts that remain the same or function the same as in the systems of  FIGS. 1–5  are identified by the same reference numerals. 
   The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.

Technology Category: 2