Abstract:
A turbine pump includes a casing having an inlet, an outlet and front and rear arc-shaped pump passages and an impeller. The impeller has plural impeller partitions respectively disposed between every two of the blades thereby forming impeller grooves at front and rear sides of the partitions and an outer ring at the peripheral edge of the blades. Each impeller groove, each of pump passage and the outer ring form a space for circulating fuel. The outside diameter of the impeller is smaller than the pump passages so that the impeller does not contact the pump passages.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
         [0001]    The present application is based on and claims priority from Japanese Patent Applications 2001-97181, filed Mar. 29, 2001 and 2002-27949, filed Feb. 5, 2002, the contents of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a turbine pump that is suitable to a fuel pump to be mounted in a fuel tank of an automotive vehicle.  
           [0004]    2. Description of the Related Art  
           [0005]    U.S. Pat. No. 5,468,119 or its corresponding publication JP-A-299983 discloses a turbine pump or peripheral pump for a fuel pump to be mounted in an automotive vehicle. The disclosed turbine pump has an outer ring at the circumference of an impeller, which is disposed in chamber walls or a pump casing. The outer ring is disposed outside the spaces (hereinafter referred to the impeller grooves) between blades of the impeller in the radial direction. The outer ring, which is disposed around the impeller grooves, has axial end surfaces flush with the axial end surfaces of the blades. The outside diameter of the impeller is larger than the outside diameter of a pump passage that is formed in the casing and the outer ring is located close to the axial end surface of the pump casing.  
           [0006]    In such a turbine pump, the axial distance between the impeller and the casing is arranged to be between several micrometers (μm) and tens of micrometers to prevent high-pressure fuel from leaking from the outlet side of the pump to the inlet side thereof.  
           [0007]    While the turbine pump is operating, the impeller moves in the axial direction due to the reaction of the pumping operation. Accordingly, the axial end surface of the outer ring of the impeller contacts the peripheral end surface of the casing.  
           [0008]    Because the outer ring is located at the outermost portion of the impeller, the circumferential speed is so high that the outer ring is subject to wear, which lowers pumping capacity and the lifetime thereof.  
         SUMMARY OF THE INVENTION  
         [0009]    Therefore, the present invention has been made in view of the above problems.  
           [0010]    It is a main object of the invention to provide a reliable turbine pump which prevents the outer ring from wearing.  
           [0011]    According to a main feature of the invention, an impeller of a turbine pump has a plurality of blades disposed in the circumferential direction thereof, a plurality of impeller partitions respectively disposed between every two of the blades thereby forming a plurality of impeller grooves at front and rear sides of the partitions and an outer ring disposed at the peripheral edge of the blades. Each impeller groove, each pump passage and the outer ring form a circular space for circulating fuel thereby pressuring and discharging the fuel. The outside diameter of the impeller is smaller than the outside diameter of the pump passages. Therefore, the peripheral portion of the impeller is disposed within the pump passages where the impeller does not contact any surface of the pump passages. It is more preferable that the axial ends of the outer ring are positioned within axial ends of the blades. In addition, the outer ring may have axial ends that are tapered off in the radially inward direction. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    Other objects, features and characteristics of the present invention as well as the functions of related parts of the present invention will become clear from a study of the following detailed description, the appended claims and the drawings. In the drawings:  
         [0013]    [0013]FIG. 1 is a partially cross-sectional side view of a turbine pump according to a first embodiment of the invention;  
         [0014]    [0014]FIG. 2 is a fragmentary enlarged cross-sectional side view of a portion of the turbine pump shown in FIG. 1 encircled by circle II;  
         [0015]    [0015]FIG. 3 is cross sectional view of a portion of the turbine pump shown in FIG. 1 cut along line III-III;  
         [0016]    [0016]FIG. 4 is a fragmentary enlarged perspective view of a portion of the turbine pump shown in FIG. 3 encircled by circle IV;  
         [0017]    [0017]FIG. 5 is a fragmentary cross-sectional view of an impeller of a turbine pump according to a second embodiment of the invention;  
         [0018]    [0018]FIG. 6 is a fragmentary cross-sectional view of an impeller of a turbine pump according to a third embodiment of the invention; and  
         [0019]    [0019]FIG. 7 is a fragmentary cross-sectional view of an impeller of a turbine pump according to a fourth embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    A turbine pump according to a first embodiment of the invention to be mounted in a fuel tank for an engine (not shown) is described with reference to FIGS.  1 - 4 .  
         [0021]    As shown in FIG. 1, a turbine pump  1  according to a first embodiment of the invention is mounted in a fuel pump  100  together with a drive motor (not shown), which are covered by a housing  101 . The fuel pump includes, besides the drivemotor, a motor shaft  102 , an electric connector  103 , a fuel chamber  104 , a fuel discharge pipe  105  and a fuel intake pipe  4   a . When electric power is supplied to the fuel pump  100  via the connector  103 , the turbine pump  1  pumps up fuel in a fuel tank from an intake pipe  4   a  and discharges the fuel from the turbine pump into the fuel chamber  104 . Thereafter, the fuel is supplied to an engine via the fuel discharge pipe  105 . The fuel chamber  104  is provided inside the drive motor.  
         [0022]    The turbine pump  1  is comprised of a pump casing  2 , an impeller  3 , and a pump cover  4 . The impeller  3  is rotatably disposed between the pump casing  2  and the pump cover  4 .  
         [0023]    The pump casing  2  is made of aluminum die-cast or strong resinous material that is resistant to fuel and has a cylindrical space  2   a  that accommodates the impeller  3 . The axial depth of cylindrical space  2   a  is a distance between several micrometers (μm) and tens of micrometers longer than the thickness of the impeller  3 . In other words, the gap between the pump cover  4  and the impeller is the same as the gap between the pump casing  2  and the impeller  3 . As shown in FIGS. 2 and 3, a pump passage  2   b  is formed to be coaxial with the cylindrical space  2   a . The pump passage  2   b  is connected to the inlet  4   c  at an end thereof and connected to the outlet  2   c  at the other end thereof. In the meantime, the inlet  4   c  is indicated in FIG. 3 by one-dot-chain line for reference. As shown in FIG. 2, radially outermost surface  2   bl  of the pump passage  2   bl  is included in the inner surface  2   al  of the cylindrical space  2   a . In other words, the outside diameter of the pump passage  2   b  is the same as the inside diameter D 2  of the cylindrical space  2   a . A plurality of blades  3   a  is formed at the axial end surface  3   g  of the impeller  3 . The radial distance between the outside diameter D 1  of the impeller  3  and the inside diameter D 2  of the cylindrical space  2   a  is designed to be the best for pump performance. That is, the outside diameter D 1  of the impeller  3  is designed to be smaller than the outside diameter of the pump passage  2   b . Accordingly, the portion of the impeller  3  whose circumferential speed is the maximum while the impeller rotates does not contact the surface of the pump passage  2   b  or any other portion of the pump casing  2 . The pump casing  2  has a bearing  5  that rotatably supports a motor shaft  102  at the center thereof.  
         [0024]    The impeller  3  is made of heat resistant resinous material and is disposed in the cylindrical space  2   a  of the pump casing  2 . As shown in FIG. 3, the impeller  3  has a plurality of blades  3   a  formed at both the peripheral front surface that faces the pump casing  2  and the peripheral rear surface that faces the pump cover  4 . The blades  3   a  formed at the front surface and the blades formed at the rear surface are disposed side by side at equal intervals in the circumferential direction. An impeller groove  3   b  is formed between each adjacent two blades  3   a . As shown in FIG. 2, impeller partitions  3   d  are disposed at an axially middle and radially inside portion thereof to protrude radially outward to divide each of the impeller grooves  3   b  into a front side groove and a rear side groove. Thus, the fuel introduced in the space (hereinafter referred to as the circular space) defined by the impeller grooves  3   b , the pump passage  2   b  of the pump casing  2  and a pump passage  4   b  of the pump cover  4  is circulated and pressured by the impeller  3 . An outer ring  3   c  is integrated with the plurality of blades  3   a  to connect the same at the edges thereof. In other words, the outer ring  3   c  closes the circumference of the impeller  3 . The axial ends of the outer ring  3   c  are positioned within the axial ends of the impeller  3 . The outer ring  3   c  has a trapezoidal cross section with the shorter side being radially inward, as shown in FIG. 2. That is, the axial length of a portion of the outer ring  3   c  becomes longer as it shifts radially outward. In other words, the outer ring  3   c  has axial end surfaces  3   f  that taper off in the radially inward direction.  
         [0025]    While the turbine pump is operating, fuel circulates in the circular spaces defined by the impeller grooves  3   b  and the pump passages  2   b  and  4   b  as indicated by arrows in FIG. 2. The above arrangement of the outer ring  3   c  is effective to smooth circulation of the fuel.  
         [0026]    The impeller  3  has a semicircular center hole  3   e , to which the motor shaft  102  is fitted to rotate the impeller  3 .  
         [0027]    The pump cover  4  is also made of aluminum die-cast or strong resinous material that is resistant to fuel. The pump passage  4   b  is formed at the portion of the pump cover  4  opposite the pump passage  2   b  to enclose the blades  3   a  of the impeller  3 . In other words, the outside diameter D 1  of the impeller  3  or the outer ring  3   c  is smaller than the outside diameter D 2  of the pump passage  4   b . Therefore, the outer ring  3   c , whose circumference speed is larger than other portions of the impeller  3 , is disposed within the pump passage  4   b  and do not contact the surface of the pump passage  4   b  or other surface of the pump cover  4  while the impeller  3  is rotating. Accordingly, the impeller  3  is not subject to wear. On the other hand, the axial end of the blades  3   a  contact the surfaces of the casing  2  and the pump cover  4  opposite the blades  3   a  to seal the portion between the outlet  2   c  and the inlet  4   c . The inlet  4   c  is formed in the pump cover  4  to connect the pump passages  2   b  and  4   b.    
         [0028]    The fuel pump  100  is assembled in the following manner.  
         [0029]    A drive motor, a motor drive unit and the connector  103  are assembled into the housing  101  and electrically connected at first. Next, the turbine pump  1  is inserted into the housing  101 . Then, the pump casing  2  is force-fitted to the housing  101 , and the motor shaft  102  is fitted to the bearing  5  as shown in FIG. 1. Thereafter, the impeller  3  is inserted into the cylindrical space  2   a  of the pump casing  2 , and the motor shaft  102  is inserted into the center hole  3   e . Next, the pump cover  3  is positioned relative to the pump casing  2  and force-fitted into the housing  101 . Finally, the edge portion of the housing  101  is clamped to fix the turbine pump  1 .  
         [0030]    When the impeller  3  is rotated by the motor in the direction indicated by an arrow in FIG. 3, fuel is pumped up from the intake pipe  4   a  and introduced into the circular space via the inlet  4   c . The fuel in the impeller grooves  3   b  is circulated in the circular space defined by the impeller grooves  3   b  and the pump passages  2   b  and  4   b . In other words, the fuel is moved radially outward by centrifugal force due to the rotation, turned by the outer ring  3   c  and introduced into the pump passage  2   b , as indicated by arrows in FIG. 2. The fuel is further guided by the inner surface of the pump passage  2   b , moved in the rotation direction of the impeller  3  and introduced into the impeller grooves  2   b . Thereafter, the fuel is moved radially outward again by the centrifugal force, turned by the outer ring  3   c  and introduced into the pump passage  2   b . Thus, the fuel is repeatedly moved and circulated to increase the pressure thereof before it is discharged from the fuel outlet  2   c . The fuel in the pump passage  4   b  is moved and circulated in the same manner as described above and shown in FIG. 2, so that two symmetrical pressuring motions of the fuel are set up in the turbine pump  1 .  
         [0031]    A turbine pump according to a second embodiment of the invention is described with reference to FIG. 5. In the meantime, the same reference numeral represents the same or substantially the same portion, part or components as the first embodiment hereafter.  
         [0032]    The outer ring  3   c  is positioned so that the axial ends thereof are located within the axial ends of the impeller  3 . However, the axial end surfaces  3   f  of the outer ring  3   c  are not tapered off but are parallel to the axial end surfaces of the impeller.  
         [0033]    A turbine pump according to a third embodiment of the invention is described with reference to FIG. 6.  
         [0034]    The outer ring  3   c  has axial end surfaces  3   f  that taper off in the radially inward direction. However, the outer ring  3   c  has the same axial length as the impeller  3  and is positioned so that the axial ends thereof are located to be flush the axial ends of the impeller  3 .  
         [0035]    A turbine pump according to a fourth embodiment of the invention is described with reference to FIG. 7.  
         [0036]    The outer ring  3   c  and the impeller grooves  3   b  are formed by a circular or cylindrical surface to be continuous so that the axial ends of the outer ring  3   c  can be positioned outside the axially innermost portion  3   dl  of the impeller partitions  3   d . The impeller grooves  3   b  are alternately formed on the front and rear surfaces of the impeller in the circumferential direction. Therefore, there is no space or opening between the outer ring  3   c  and the impeller partitions  3   d . Because the outer ring  3   c  and the impeller partitions  3   d  formed by a cylindrical surface to be continuous, the fuel can circulate more smoothly.  
         [0037]    In this embodiment, the axial end of the outer ring  3   c  can be tapered as the outer ring  3   c  shown in FIG. 2.  
         [0038]    In the foregoing description of the present invention, the invention has been disclosed with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific embodiments of the present invention without departing from the scope of the invention as set forth in the appended claims. Accordingly, the description of the present invention is to be regarded in an illustrative, rather than a restrictive, sense.