Patent Publication Number: US-6669437-B2

Title: Regenerative fuel pump with leakage prevent grooves

Description:
TECHNICAL FIELD AND BACKGROUND OF THE INVENTION 
     This invention relates generally to pumps, and in particular to vaned impeller pump useful as an electric-motor-operated fuel pump for an automotive vehicle to pump liquid fuel from a fuel tank through a fuel handling system to an engine that powers the vehicle. 
     In an automotive vehicle that is powered by an internal combustion engine, fuel that may be pumped through a fuel handling system of the engine by an in-tank, electric-motor-operated fuel pump. 
     Examples of fuel pumps are shown in various patents, including U.S. Pat. Nos. 3,851,998; 5,310,308; 5,409,357; 5,415,521; 5,551,875; 5,601,308; and 5,904,468. Commonly owned U.S. Pat. Nos. 5,310,308; 5,409,357; 5,551,835; 5,375,971; and 5,921,746 disclose pumps of the general type to which the present invention relates, and such pumps provide certain benefits and advantages over certain other types of pumps. One benefit of such pumps is that a number of its parts may be fabricated from polymeric (i.e. plastic) materials. 
     Through the continuing development of such pumps, it has been discovered that the presence of certain particulate material in commercial fuel may abrade such synthetic materials and thereby encourage wearing of pump parts made of such materials. Because vanes of a plastic impeller of such a pump are quite small, and because running clearances between pumping chamber walls and such an impeller may also be small, it is believed desirable to reduce the extent of interaction of such particulate material with the internal pumping mechanism. Because an automotive vehicle manufacturer cannot at the present time reasonably rely on commercial fuel refiners to improve fuel purity, is has become incumbent on the vehicle manufacturer to find a solution. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a solution for the situation just described. In this invention the or more grooves are provided in the seal surface between inlet and outlet, which is called the “strip area”. The grooves extend radially outward, and the length is about the same width as flow channels. The width of the channel is about 1 mm, and the depth of the grooves is about 1.0-1.5 mm. Each groove has a smooth upward ramp to match the vortex path, and reduce flow losses. The shape of the grooves can be flat in the bottom, circular, or elliptical shape. 
     There are three functions of this invention so called “leakage prevent grooves”. They reduce the contact surface of the impeller/cover, and reduce the friction torque; the grooves match the vortex path, clean the contamination in the area, and reduce the chance of wear between impeller/cover. If impeller/cover does wear because of the contamination, the radial directional grooves act like seal grooves and reduce the leakage between inlet/outlet. 
     Other general and more specific aspects will be set forth in the ensuing description and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings that will now be briefly described are incorporated herein to illustrate a preferred embodiment of the invention and a best mode presently contemplated for carrying out the invention. 
     FIG. 1 is a longitudinal cross section view of a fuel pump embodying principles of the invention; 
     FIG. 2 is an enlarged fragmentary cross sectional view of part of the pumping element and showing the vortex paths; 
     FIG. 3 is an enlarged view of one part of the fuel pump of FIG. 1, namely a vaned pumping element, by itself; 
     FIG. 4 is a full view of the pumping element in the direction of arrows  4 — 4  in FIG. 3; 
     FIG. 5 is an enlarged view in the direction of arrows  5 — 5  in FIG. 1; 
     FIG. 6 is an enlarged view in the direction of arrows  6 — 6  in FIG. 1; 
     FIG. 7 is a sectional view of the pump as seen from arrows from FIG. 6; 
     FIGS. 8,  9 , and  10  are enlarged views of three different leakage prevent grooves shown in FIG.  5  and FIG. 7; 
     FIGS. 11,  12 ,  13 , and  14  are enlarged fragmentary cross section views taken through a pump at locations respectively represented by sections lines  11 — 11 ,  12 — 12 ,  13 — 13 , and  14 — 14  in FIG. 5; and 
     FIG. 15 is an enlarged perspective view of the leakage prevent grooves and their position near the entry to the pump passage. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiments of the invention is not intended to limit the scope of the invention to these three embodiments, but rather to enable any person skilled in the art to make and use the invention. 
     An automotive vehicle fuel pump  20  embodying principles of the present invention, and having an imaginary longitudinal axis  21 , is shown in FIG. 17 to comprise a housing  23  that includes a pump wall  22  and a pump cover  24  cooperatively arranged to close off one axial end of a cylindrical sleeve  26  and to cooperatively define an internal pumping chamber  27  within which a pumping element  28  is disposed for rotation about axis  21 . The opposite axial end of sleeve  26  is closed by a part  30  that contains an exit tube  32  via which fuel exits pump  20 . Part  30  is spaced from pump cover  24  to provide an internal space for an electric motor  34  that rotates pumping element  28  when pump  20  runs. Motor  34  comprises an armature including a shaft  38  journaled for rotation about axis  21  and having a keyed connection at one end for imparting rotational motion to pumping element  28 . 
     Pump  20  is intended to be at least partially submerged in a fuel tank of an automotive vehicle for running wet. A passage that extends through pump bottom  22  provides an inlet  36  to pumping chamber  27 . A passage that extends through pump cover  24  provides an outlet  40  from pumping chamber  27 . Fuel that leaves outlet  40  passes through pumping chamber  27 . Fuel that leaves outlet  40  passes through motor  34  and exits pump  20  via tube  32  from whence the fuel is pumped to an engine through an engine fuel handling system (not shown). 
     Pumping chamber  27  comprises a main channel  42  as shown in FIG. 5, extending arcuately about axis  21  in pump bottom  22  to one axial side of pumping element  28 . As seen in FIG. 5, main channel  42  has a circumferential extent of more than 270°, but less that 360°. From a location  44  immediately proximate inlet  36 , to a location  46  immediately proximate outlet  40 , main channel  42  is essentially circular, having a substantially constant radial dimension. In radial cross section, main channel  42  is concave, as shown in FIGS. 1,  2 , and  3 . A further portion of pumping chamber  27  is provided by a main channel  48  formed in pump cover  24  opposite, and similar in geometry to, main channel  42 . 
     Pumping element  28  comprises a circular body  50  having a series of circumferentially spaced apart vanes  52  with a ring around its outer periphery. As pumping element  28  is rotated by motor  34 , its vaned periphery is effective to create a pressure differential between inlet  36  and outlet  40  that pushes fluid through tube  30  and motor  34 , and forces the fluid out of pump  20  through outlet  32 . 
     In accordance with certain inventive principles, main channel  42  has a radially outer margin that opens along at least a portion of its arcuate extent to an adjoining contaminant collection channel  56  that extends arcuately about axis  21 . The open area is designated by the reference numeral  58 . In radial cross section, channel  56  is shown to be much smaller than main channel  42 . As a pumping element  28  rotates, certain fluid-entrained particulates in fuel moving through the pump are propelled from main channel  42  through the open area  58 , presumptively by centrifugal forces. Contaminant collection channel  56  is effective to contain and convey such collected particulates in a direction toward outlet  40 . Contaminant collection channel  56  is dimensioned in relation to main channel  42  such that the presence of contaminant collection channel  56  in pump  20  creates no substantial change in pumping efficiency in comparison to a like pump that lacks contaminant collection channel  56 . 
     Beyond location  46 , main channel  42  contracts to form an ending section  16  for transitioning the fuel flow toward outlet  40 . At the end of the contaminant collection channel  56  proximate outlet  40 , a sump  62  is disposed outwardly adjacent ending section  16 . Sump  62  is formed by an undercut in the same face of pump bottom  22  that contains contaminant collection channel  56 . Sump  62  provides a volume where particulates that have been conveyed to is through channel  56  may collect before they are expelled from pump  20 . Because outlet  40  is in pump cover  24 , a slot  64  bridges sump  62  to outlet  40  radially outwardly of the periphery of both pumping element  28  and ending section  16 . In this way slot  64  provides an escapement for particles to pass from sump  62  to outlet  40  out of the path of the rotating pumping element  28 . 
     FIGS. 8,  9  and  10  are side elevational cross-sectional views of three different leakage prevent grooves shown in FIG. 5 on the pump bottom  22 . There are several grooves laid in the seal surface between the “in” and “out” surface. FIG. 8 shows a groove  61  having a flat bottom  63  and inclined ends  65  that are angled to match the impeller vane angles. The length of the groove  61  is about the same width as the flow channel  42 . The width is about 1 mm and depth of the grooves is about 1.0-1.5 mm. At each end of the groove there is a smooth upward ramp to match the vortex path and reduce flow losses. The shape of these grooves could be flattened in the bottom, circular, or elliptical shape. 
     FIG. 9 shows a groove  67  which has an elliptical bottom  69  and FIG. 10 shows a similar groove  70  which has a circular bottom  72  as described above. It is seen that there are three functions of this invention in providing the “leakage prevent grooves  61 ,  67 , and  70 .” The grooves  61 ,  67 , and/or  70 , as seen in FIG. 15, can be used singly, or in greater number or mixed grooves. First, a groove reduces the contact surface of the impeller/cover and reduces friction torque. Second, each groove matches the vortex path, cleaning the contamination in the area and reducing the chance of wear between impeller and cover surface. If impeller and cover surfaces wear because of the contamination the radial directional grooves act like sealed grooves to reduce the leakage between inlet and outlet. 
     Contaminant collection channel  56  may, as shown by FIGS. 11-14, be considered to comprise two side wall surfaces  56   a ,  56   b , and an end wall surface  56   c . These figures also show a geometry that is believed desirable for aiding containment of particulate matter in channel  56 , once such matter has entered the channel. Along an initial portion of channel  56  extending from location  44 , wall surfaces  56   a ,  56   b  may be uniformly spaced apart and parallel, making the axial dimension of open area  58  constant. As contaminant collection channel  56  approaches sump  62 , wall surfaces  56   a ,  56   b  may depart from parallelism, while retaining flatness. For example, wall surface  56   b  may begin to incline slightly so as to cause a progressive decrease in the axial dimension of open area  58 , and a corresponding decrease in cross sectional area of contaminant collection channel  56  as viewed circumferentially of channel  56 . It is believed that this gradual constriction aids the containment of particles moving through channel  56  and their eventual expulsion from the pump. Because known flow principles hold that decrease in cross sectional area available for flow creates corresponding increase in flow velocity, it is believed that acceleration is imparted to particles as they move along channel  56 , promoting the immediately flushing of particles out of the pump instead of their accumulation in sump  62 . Illustrative measurements for dimensions “A”, “C” in all of FIGS. 11-14, and for dimensions “D1”, “D2”, “D3”, and “D4” in respective ones of FIGS. 11-14 are as follows: “A”=0.100 mm.; “C”=0.070 mm; “D1”=0.070 mm; “D2”=0.070 mm; “D3”=0.030 mm; and “D4”=0.010 mm. 
     It is believed that pumps embodying principles that have been described and illustrated herein can improve pump performance and durability. 
     The foregoing discussion discloses and describes two preferred embodiments of the invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that changes and modifications can be made to the invention without departing from the true spirit and fair scope of the invention as defined in the following claims. The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.