The invention relates generally to regenerative turbine pumps of the type that are used to pump fuel from a fuel tank to an engine of a motor vehicle. More particularly, the invention pertains to an improved V-blade impeller, for a regenerative turbine pump, whose design not only improves the overall mechanical efficiency of the high pressure section of the pump but also retains the ability to be manufactured by conventional low-cost injection molding techniques.
The following background information is provided to assist the reader to understand the environment in which the invention will typically be used. Upon reading this document, the reader will appreciate that the invention may also be applied or adapted to environments other than that described below.
As used in the fuel system of a motor vehicle, a regenerative turbine pump is intended to provide the engine of the vehicle with fuel at relatively high pressure at moderate flow rates. U.S. Pat. Nos. 5,580,213, 5,509,778, 5,393,206, 5,393,203, 5,280,213, 5,273,394, 5,209,630, 5,129,796, 5,013,222 and 4,734,008 are generally representative of the variety of regenerative turbine fuel pumps used in the automotive industry. The teachings of these earlier patents are therefore incorporated into this document by reference.
FIGS. 1-6 illustrate one type of regenerative turbine fuel pump, generally designated 10, along with its associated structure and internal components. This regenerative turbine pump 10 is housed within a tubular metal shell 14, also referred to in the literature as a pump housing. Encased within this metal shell 14 is an electric motor 18. The motor 18 is built around an armature shaft 20, as is well known in the art, and is positioned within the housing 14 so that the shaft 20 can be rotated about a longitudinal center axis 4. Projecting from one end of the housing 14 is a terminal 11. It is through this terminal 11 via a wiring harness (not shown) on the vehicle that electrical energy can be supplied to the electric motor 18.
As best shown in FIGS. 1 and 2, an impeller 12 is mounted to one end of the shaft 20. The impeller 12 is situated between a pair of generally cylindrical plates 22a and 22b. Between the plates 22a and 22b there is defined a generally disk-shaped space 24 within which the impeller 12 is designed to rotate. This space 24 is best shown in FIG. 4. An annular groove 23a in the inside face of outer plate 22a cooperates with an annular groove 23b in the outside face of inner plate 22b to form an annular pump channel 23. As best shown in FIGS. 3 and 4, the outer plate 22a also defines an inlet port 34 that communicates with annular groove 23a. Similarly, the inner plate 22b defines an outlet port 36 that communicates with annular groove 23b. 
The fuel tank of the vehicle communicates with the annular pump channel 23 through the inlet port 34 in outer plate 22a. This communication occurs through the annular groove 23a on the inlet side of impeller 12, as well as through known passageway(s) internal to fuel pump 10. The pump housing 14 has a discharge tube 48 to which the outlet port 36 is connected via other known passageway(s) within the fuel pump 10. Through outlet port 36, discharge port 48 communicates with the annular pump channel 23 on the outlet side of impeller 12, i.e., through annular groove 23b. It is from this discharge tube 48 that pressurized fuel is discharged from and delivered by the fuel pump 10 for use by the engine of the vehicle.
The impeller 12 serves as the rotary pumping element for the regenerative turbine pump 10. As shown in FIGS. 1-5, the impeller 12 basically takes the form of a disk having a hub 26 whose axis of rotation is centered on center axis 4. The hub 26 defines an aperture 28 at its center. The aperture 28 is notched, to accommodate the like-shaped shaft 20 of motor 18. The notched aperture 28 allows the shaft 20 to drive the impeller 12 when the electrical motor 18 is activated.
The impeller 12 has a plurality of fan blades 30 that project radially outward from the hub 26. Also referred to as vanes, the fan blades 30 are generally spaced from each other uniformly. As best shown in FIGS. 4-6, each of the vanes 30 is V-shaped. Radiating from the periphery of hub 26, the vanes are situated in between and adjacent to the annular grooves 23a and 23b in outer and inner plates 22a and 22b, respectively. In other words, the vanes 30 are positioned directly within the annular pump channel 23 of the regenerative turbine pump 10.
FIGS. 5 and 6 illustrate the structure of the vanes 30. Each V-shaped blade 30 has a pair of fin members 30a and 30b, each having a generally rectangular cross-section. The base of each fin member emanates from the hub 26. Each fin member 30a and 30b lies at angle of approximately 45xc2x0 with respect to a plane of intersection 5 that bisects impeller 12 longitudinally. This plane appears as a line in FIG. 6, as two fan blades 30 of impeller 12 are viewed therein from the top. The inner sidewalls 31a and 31b of fin members 30a and 30b are formed together along the plane 5 during the injection molding process that is used to manufacture the impeller 12. From their adjoined inner sidewalls, the fin members of each vane 30 diverge away from each other. These adjoined fin members 30a and 30b together form upstream and downstream faces. Facing the direction of rotation 6, the upstream face of each vane 30 is generally concave, exhibiting an angle of approximately 90xc2x0. The downstream face is convex, exhibiting a similar angle on the back side of vane 30. Each vane 30 also has two generally flat outer sidewalls 32a and 32b. Fin member 30a has outer sidewall 32a and fin member 30b has outer sidewall 32b. 
FIG. 5 best illustrates how the vane(s) 30 are oriented with respect to, and are moved within, the annular pump channel 23. FIG. 5 shows the annular groove 23a in the inside face of outer plate 22a. The annular groove 23b in the outside face of inner plate 22b is best shown in FIG. 2. Outer sidewall 32a lies directly adjacent to annular groove 23a, and outer sidewall 32b lies adjacent to annular groove 23b. The vanes 30 of impeller 12 thus lie within the annular pump channel 23 that is defined by annular grooves 23a and 23b. The annular pump channel 23 essentially encompasses the vanes 30 of impeller 12.
The regenerative turbine fuel pump 10 operates as follows. When electricity is supplied via terminal 11 to the electric motor 18, the armature shaft 20 immediately begins to rotate. The rotation of shaft 20, in turn, causes the impeller 12 to rotate within the disk-shaped space 24 between the inner and outer plates 22a and 22b. Fuel from the fuel tank is sucked into the inlet port 34 and flows into the annular groove 23a, and thus into the annular pump channel 23. As the impeller 12 rotates, its V-shaped vanes 30, in combination with annular grooves 23a and 23b on either side, cause the fuel to whirl about the annular pump channel 23 in a toroidal flow path, as is best shown in FIG. 5. In particular, as impeller 12 rotates, the fuel exits each vane 30 at the tip and then re-enters the base of the trailing vane 30. As is known in the art, this regenerative cycle of exiting the tip of the leading blade 30 and entering the base of the trailing blade 30 occurs many times as the fuel is conveyed through the annular pump channel 23 by the vanes 30 moving on the periphery of impeller 12.
As the impeller rotates, the movement of the V-shaped vanes 30 through the annular pump channel 23 imparts momentum to the fuel as it flows along the toroidal flow path. On the outlet side of impeller 12 (i.e., through annular groove 23b), the fast moving fuel then flows through the outlet port 36 defined in inner plate 22b. From the outlet port 36, the fuel continues flowing through the internal passageway(s) of the housing 14 and exits the fuel pump 10 through discharge port 48. In this known manner, fuel at relatively high pressure is provided to the engine of the motor vehicle at an appropriate rate of flow.
The efficiency of a regenerative turbine fuel pump (10) is limited by the loss of energy from the flow of fuel caused by the non-streamlined design of the vanes (30). The efficiency is also limited in that the injection molding process used to make such an impeller (12) requires relatively thick vane profiles.
There are at least two disadvantages inherent to the type of regenerative turbine fuel pump 10 described above. The shortcomings of interest in this document can be traced to the design of the impeller 12. With its V-shaped vanes 30, the impeller 12 is, of course, the rotary pumping element that is responsible for increasing the momentum of the fuel with each regenerative cycle. Nevertheless, the impeller 12 has at least two design flaws that result in lowering the momentum of the fuel as it enters each of the fan blades 30.
The first design flaw involves the downstream face of each vane 30. Specifically, some energy in the stream of fuel is lost behind each blade 30 due to the separation of the fluid stream and the low pressure area resulting therefrom. The area where this energy loss occurs is depicted at L1 in FIG. 6, generally just behind the trailing corner 33 of each fin member.
The second design flaw involves the upstream face of the vanes 30. In particular, the flow of fuel loses more energy at the point at which the fuel impacts the leading corners of each fan blade 30. The area where this energy loss occurs is depicted at L2 in FIG. 6. The combined losses due to separation and low pressure behind each blade 30 and impact of the fuel on the forward facing corners of each blade 30 serve not only to decrease the rate at which the fuel flows but also the pressure at which the fuel is provided to the engine.
It is, therefore, an objective of the invention to provide a new and improved impeller for a regenerative turbine pump that improves the overall mechanical efficiency of the high pressure section of the fuel pump and yet still retains a geometry that allows it to be manufactured by conventional injection molding techniques at a relatively low cost.
Another objective is to provide a new and improved impeller for a regenerative turbine pump that minimizes energy losses associated with the circulatory flow of the fuel impacting against the forward faces of the vanes as well as energy losses caused by the separation of the fuel stream behind the vanes.
A related objective is to provide an impeller whose vanes are designed to reduce the amount of energy lost from the fuel stream by minimizing the separation of the fuel stream behind each vane and the development of a low pressure area thereat.
Another related objective is to provide an impeller whose vanes are designed to reduce the amount of energy lost from the fuel stream by lessening the force with which the circulating fuel stream impacts the forward facing corners of each vane.
In addition to the objectives and advantages listed above, various other objectives and advantages of the invention will become more readily apparent to persons skilled in the relevant art from a reading of the detailed description section of this document. The other objectives and advantages will become particularly apparent when the detailed description is considered along with the accompanying drawings and claims.
The foregoing objectives and advantages are attained by a novel impeller for a regenerative turbine fuel pump. The fuel pump for which the impeller is designed should have an electrical motor and a shaft rotatable thereby about a center axis in a forward direction. In its preferred and alternative embodiments, the novel impeller comprises a hub and a plurality of innovative V-shaped vanes. The hub defines an aperture into which the shaft of the fuel pump is securable to allow the hub to rotate with the shaft about the center axis. The plurality of V-shaped vanes project radially outward from a cylindrical outer surface of the hub. Each V-shaped vane comprises a pair of fin members. Each fin member has an inner sidewall and an outer sidewall. The fin members of each vane are adjoined by their inner sidewalls. From their adjoined inner sidewalls, the fin members of each vane diverge to their respective outer sidewalls. More specifically, the fin members of each vane diverge at a prespecified angle relative to a plane that lies normal to the center axis and also bisects the hub. The fin members of each vane thus present an upstream face and a downstream face. The novelty resides principally in the trailing corners of each outer sidewall. Each outer sidewall of each vane is chamfered along at least part of the length of its trailing corner. The chamfer is made at a predetermined angle relative to the aforementioned plane.
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