REGENERATIVE PUMP WITH TWO-STAGE STRIPPER

Abstract: A regenerative rotary pump (36) in an automotive fuel pump assembly (16). The rotary pump (36) has a disc-shaped impeller (70) in a circular cavity of a housing (38,40), vanes (74) around the circumference of the impeller (70) separated by pockets (76), a doughnut-shaped pumping chamber (64) in the housing (38,40) enveloping the vanes (74) and the pockets (76) on the impeller (70), a two-stage stripper (78) between a discharge (68) at a high-pressure end of the pumping chamber (64) and an inlet (66) at a low-pressure end of the pumping chamber (64), and a vent chamber (84) between a high-pressure stage (80) and a low-pressure stage (82) of the two-stage stripper (78). The vent chamber (84) is connected to the fuel tank (10) at a point (88) removed from the inlet (66). High-pressure gasoline carried by the pockets (76) between the vanes (74) flashes into vapor in the vent chamber (84) to minimize the vapor jet stream effect at the inlet end of the pumping chamber (64).

Description: This invention relates generally to rotary pumps and, more particularly, to regenerative pumps in automotive fuel pump applications as specified in the preamble of claim 1, for example as disclosed in US-A-4,538,958. In so-called "regenerative" rotary pumps, a disc-shaped impeller with vanes around its circumference rotates at relatively high speed in a housing having a doughnut-shaped pumping chamber enveloping the circumference of the impeller. The pumping chamber is interrupted by a reduced cross-section portion, commonly referred to as a "stripper", which separates a pumping chamber inlet from a pumping chamber discharge. During each revolution of the impeller, the vanes move fluid from the inlet to the discharge whilst interacting with the surrounding pumping chamber to boost the pressure of the fluid at the discharge. The stripper isolates the discharge from the inlet except for individual volumes, i.e., slugs, of high-pressure fuel trapped between the vanes as they traverse the stripper and any blow-by or leakage of fuel across the stripper through the running clearance between the impeller and the housing. Under high ambient temperature conditions or high gasoline fuel temperature in automobile fuel pump applications, high-pressure gasoline trapped between the vanes and/or leaking across the stripper may flash to vapor near the pumping chamber inlet and create a jet stream cavitation effect disturbing the flow characteristics at the inlet. A regenerative pump according to this invention includes a stripper which relieves the pressure of the trapped gasoline to minimize the jet stream cavitation effect. A regenerative rotary pump in an automotive fuel pump assembly according to the present invention is characterised by the features specified in the characterising portion of claim 1. This invention is a new and improved regenerative type rotary pump particularly suited for automobile fuel pump applications. The regenerative pump according to this invention includes a disc-shaped impeller having a plurality of vanes around its circumference, a housing having a doughnut-shaped pumping chamber surrounding the vanes on the impeller, and a two-stage pressure-vented stripper between a pumping chamber inlet and a pumping chamber discharge. The pressure-vented stripper has a high-pressure stage adjacent the pumping chamber discharge, a low-pressure stage adjacent the pumping chamber inlet, and a vent between the high-pressure and low-pressure stages connected to the fuel tank at a location removed from the pumping chamber inlet. The high-pressure fuel trapped between the vanes and/or leaking across the stripper from the high-pressure end of the pumping chamber encounters the vent between the high-pressure and low-pressure stages of the stripper where pressure is relieved so that only low-pressure fuel remains trapped between the vanes and little or no gasoline leaks across the low-pressure stage of the stripper to the pumping chamber inlet. The vent is connected to the fuel tank at a location removed from the pumping chamber inlet so that vapor generated at the vent is not drawn in at the inlet. The invention and how it may be performed are hereinafter particularly described with reference to the accompanying drawings, in which: Figure 1 is a fragmentary elevational view, partially in section, of an automobile fuel tank having a submerged fuel pump assembly including a regenerative pump according to this invention; Figure 2 is an enlarged partially broken-away view of a portion of Figure 1; Figure 3 is a view taken generally along the plane indicated by lines 3-3 in Figure 2; Figure 4 is a view taken generally along the plane indicated by lines 4-4 in Figure 2; and Figure 5 is a sectional view taken generally along the plane indicated by lines 5-5 in Figure 4. Referring to Figures 1 and 2, an automobile fuel tank 10 has an interior fuel chamber 12, one side of which is defined by a bottom wall 14 of the tank. A fuel pump assembly 16 is suspended within the fuel chamber 12 adjacent the bottom wall 14 on a lower end of a fuel discharge tube 18 through which the pump assembly 16 supplies fuel to the engine of the vehicle. The pump assembly 16 is normally submerged in gasoline. A schematically-illustrated wiring harness 20 conducts current to an electric motor of the pump assembly 16 whereby operation of the pump assembly is synchronized with the state of the ignition of the vehicle. An elastomeric bumper 22 connected to the pump assembly 16 bears against the bottom wall 14 to control vibration of the pump assembly 16. A tubular inlet screen 24 of the fuel pump assembly is attached to the pump assembly 16. The electric motor of the fuel pump assembly forms no part of this invention and may be of the type described in US-A-3418991 and US-A-4209284. Briefly, the motor includes a cylindrical flux ring 26 within a generally tubular shell 28 of the pump assembly 16. The motor has an armature shaft 30 which is rotatable about a longitudinal axis 32 of the shell 28 when the motor is turned on. The armature shaft is disposed in an internal volume 34 of the shell 28 which communicates with the fuel discharge tube 18. A regenerative pump 36 according to this invention closes the right-hand end, as seen in Figure 2, of the shell 28 and is driven by the armature shaft 30. Referring to Figures 2-5, the regenerative pump 36 includes a first housing 38 and a second housing 40. The first housing 38 has a cylindrical outside wall 42 closely received in and keyed or otherwise non-rotatably connected to an enlarged portion 44 of the shell 28. The second housing 40 is generally disc-shaped and has a circular end wall 46 perpendicular to the axis 32. The end wall 46 abuts a similar end wall 48 of the first housing 38. The shell 28 is crimped over an annular shoulder 50 on the second housing 40, Figure 2, whereby the first and second housings 38 and 40 are pressed tightly together at the interface between end walls 46 and 48. A cylindrical flange 52 on the second housing 40 defines a mounting detail for the tubular screen 24. The armature shaft 30 is rotatable in a bore 54 in the first housing 38 aligned on the axis 32. The armature shaft projects through the bore 54 into a circular cavity in the end wall 48 of the first housing. As seen best in Figures 2 and 5, the circular cavity has a bottom wall 56 and a cylindrical side wall 58. The bottom wall 56 has an annular groove 60 therein immediately adjacent the side wall 58. The open side of the circular cavity is closed by the end wall 46 of the second housing 40 which co-operates with the bottom wall 56 in defining the ends of the circular cavity. An annular groove 62 is defined in the end wall 46 of the second housing 40 opposite the annular groove 60 in the bottom wall 56 of the circular cavity. The grooves 60 and 62 co-operate with the side wall 58 and the portion of the circular cavity between the grooves in defining a generally doughnut-shaped pumping chamber 64 in a plane perpendicular to and centred around the axis 32. As seen best in Figures 2-4, the pumping chamber 64 communicates with the fuel chamber 12 of the tank 10 through an inlet 66 located inside the flange 52. All fuel flowing into the inlet 66 is filtered by the screen 24. The pumping chamber 64 communicates with the internal volume 34 in the shell 28 through a discharge 68. A disc-shaped impeller 70 is disposed within the circular cavity and connected to the armature shaft 30 for rotation as a unit therewith. The impeller 70 has a pair of flat, circular sides 72A-B which face, respectively, the bottom wall 56 of the circular cavity and the end wall 46 of the second housing 40. The impeller 70 fills substantially the entire circular cavity except for the pumping chamber 64 which envelops the circumference of the impeller. A plurality of so-called closed-type vanes 74 are formed around the circumference of the impeller and are located within the pumping chamber 64. The vanes are separated by a plurality of pockets 76 in the impeller which open radially and through the sides 72A-B of the impeller into the pumping chamber 64. As seen best in Figure 3, the cross-section of the pumping chamber 64 is reduced in the clockwise angular interval between the discharge 68 and the inlet 66 by a vented stripper 78 which closely receives the circumference of the impeller 70. The vented stripper 78 includes a high-pressure stage 80 immediately adjacent the discharge 68 and a low-pressure stage 82 immediately adjacent the inlet 66. The high-pressure and low-pressure stages 80 and 82 are separated by a vent diffuser chamber 84 the sides of which diverge in a general V-shape from the circular cavity. The vent chamber 84 communicates with the fuel chamber 12 of the tank 10 through an arc-shaped duct 86 and a vapor bleed restriction 88 at the end of the duct. Restrictions having diameters in the range of 0.89-1.78 mm (0.035 - 0.070 inches) have been found optimum. The bleed restriction 88 is removed from the inlet 66 outside the flange 52, see Figure 4. The regenerative pump 36 operates as follows. When the motor of the pump assembly 16 is turned on, the armature shaft 30 rotates the impeller 70 clockwise, as seen in Figure 3. Impeller speeds may be in the range of about 1500-10000 RPM. The vanes 74 on the impeller traverse the pumping chamber 64 in the direction proceeding from the inlet 66 to the discharge 68. With the pump submerged, gasoline fills the inlet 66 and is moved by the vanes 74 along the pumping chamber towards the discharge 68. With a flow restriction downstream of the discharge 68, the vanes 74 co-operate with the pumping chamber in known regenerative pump fashion to increase the pressure of the gasoline from about ambient pressure at the inlet to a higher pressure at the discharge which may be in the range of 20.68 - 723.95 kPa (3-105 PSI). Due to the close-running clearance between the high-pressure stage 80 of the stripper 78 and the impeller 70, substantially only the high-pressure gasoline in the pockets 76 between the vanes is carried by the impeller 70 from the discharge end of the pumping chamber 64 towards the inlet end of the pumping chamber. When the succeeding pockets of high-pressure gasoline, and any leakage between the impeller and the high-pressure stage 80 of the stripper, encounter the vent chamber 84, the pressure of the gasoline drops rapidly to about ambient pressure due to the connection to the fuel chamber 12 through the duct 86 and bleed 88. If the temperature of the gasoline is high, as on a hot summer day, the gasoline may flash to vapor in the vent chamber 84. The vapor is transported to the fuel chamber 12 through the duct 86 and vapor bleed 88. Because the vapor bleed is removed from the inlet 66, the flow characteristics of the gasoline at the inlet are not disturbed. The residual low-pressure gasoline in the pockets 76 between the vanes 74 is transferred by the impeller from the vent chamber 84 across the low pressure stage 82 of the stripper to the inlet end of the pumping chamber 64. Because the residual fuel is at substantially ambient pressure, there is no tendency for it to vaporize at the inlet end nor is there any tendency for gasoline or vapor to leak from the vent chamber 84 to the inlet end of the pumping chamber. Consequently, there is possibly only a very weak flow-disturbing vapor jet stream cavitation effect near the inlet 66.

Claims: A regenerative rotary pump (36) in an automotive fuel pump assembly (16), said pump (36) comprising: a housing (38,40) defining a circular cavity having a cylindrical side wall (58) and a pair of circular end walls (46,56); opposed annular grooves (60,62) formed in respective ones of said circular end walls (46,56) adjacent said cylindrical side wall (58) and co-operating therewith to define an annular pumping chamber (64); a disc-shaped impeller (70) supported in said circular cavity for rotation in a pumping direction, said impeller (70) including circumferentially-spaced vanes (74) around the periphery thereof in said pumping chamber (64), said vanes being separated from one another by pockets (76) open to said pumping chamber (64); a fluid inlet (66) on said housing (38,40) connected to said pumping chamber (64) and to a source of fluid fuel at substantially ambient pressure; and a fluid discharge (68) on said housing from said pumping chamber that is angularly spaced from said inlet (66) in said pumping direction of rotation of said impeller (70) and is connected to a flow restriction (78) on said housing downstream of said fluid discharge (68) so that said vanes (74) co-operate with said pumping chamber (64) in moving said fluid from said inlet (66) towards said discharge (68) and in increasing the pressure of said fluid at said discharge (68), characterised in that said flow restriction (78) on said housing defines, firstly, a high-pressure stripper stage (80) adjacent said discharge (68) closely receiving said impeller (70) so that direct communication between said discharge (68) and said inlet (66) in said pumping direction of rotation of said impeller (70) is substantially prevented; secondly, a low-pressure stripper stage (82) between said high-pressure stripper stage (80) and said inlet (66) closely receiving said impeller (70); thirdly, a vent chamber (84) between said high-pressure stripper stage (80) and said low-pressure stripper stage (82) that is exposed to said pockets (76) on said impeller (70); and, fourthly, a vapor bleed (86,88) between said vent chamber (84) and said source of fluid fuel at ambient pressure at a location removed from said inlet (66). A regenerative rotary pump (36) according to claim 1, characterised in that said vanes (74) on said impeller (70) are closed-type vanes. A regenerative rotary pump (36) according to claim 2, characterised in that said source of fluid at substantially ambient pressure is an automobile fuel tank (10) and said housing (38,40) is normally immersed in liquid fuel in said fuel tank (10). A regenerative rotary pump (36) according to claim 3, characterised in that a screen (24) is disposed between said fuel tank (10) and said inlet (66), and said vapor bleed (86,88) exits to said fuel tank (10) outside of said screen (24).

Inventors: VANSADIA, GHANSHYAMSINH DHARMENDRASINH
Applicants: GENERAL MOTORS CORPORATION
Application year: 1990
Main classification: F04D5
IPC codes: F02M37, F04D5