Title:
Centrifugal fluid pump
Kind Code:
A1


Abstract:
A centrifugal fluid pump for circulating fluid through an engine's cooling system includes a body configured to be at least partially received within a bore in the engine, a shaft having an impeller rotatably connected to the body, the impeller being positioned to move fluid through the engine, and a shroud supported on the body and positioned between the duct and the impeller when the body is at least partially received within the bore. The shroud has an opening to permit the movement of fluid to the impeller and may be configured to engage an inner surface of the bore. The shroud remains stationary with respect to the bore as the shaft and the impeller rotate and the shroud and the bore cooperate to inhibit fluid from passing between the inner surface of the bore and the shroud to a position that is upstream of the shroud.



Inventors:
Pipkorn, Nicholas T. (Gladstone, MI, US)
Application Number:
11/644065
Publication Date:
06/26/2008
Filing Date:
12/22/2006
Assignee:
EMP Advanced Development, LLC (Escanaba, MI, US)
Primary Class:
International Classes:
F01P5/10
View Patent Images:
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Primary Examiner:
LEUNG, KA CHUN A
Attorney, Agent or Firm:
Brooks Kushman (Southfield, MI, US)
Claims:
What is claimed is:

1. A centrifugal fluid pump for circulating fluid through an engine, the engine having a bore to receive the pump and a duct to direct fluid radially into the pump, the engine further having a block with a discharge port formed therein to receive fluid discharged from the pump, the centrifugal fluid pump comprising: a body configured to be at least partially received within the bore; a shaft rotatably connected to the body; an impeller fixed to the shaft and rotatable therewith, the impeller being positioned to move fluid from the duct to the discharge port when the body is at least partially received within the bore; and a shroud supported on the body and positioned between the duct and the impeller when the body is at least partially received within the bore, the shroud having an opening to permit movement of fluid from the duct to the impeller, the shroud being configured to engage an inner surface of the bore and the shroud remaining stationary with respect to the bore as the shaft and the impeller rotate, whereby when the body is at least partially received within the bore, the shroud and the bore cooperate to inhibit the fluid that is received in the discharge port from flowing between the inner surface of the bore and the shroud to a position upstream of the shroud.

2. The centrifugal fluid pump of claim 1 further comprising a seal arrangement disposed along an outer surface of the shroud to form a seal between the outer surface of the shroud and the inner surface of the bore when the body is at least partially received within the bore to further inhibit the fluid that is received in the discharge port from flowing between the inner surface of the bore and the outer surface of the shroud to a position upstream of the shroud.

3. The centrifugal fluid pump of claim 2 wherein the seal arrangement includes an o-ring seal.

4. The centrifugal fluid pump of claim 2 wherein the outer surface of the shroud defines a groove to receive the seal arrangement.

5. The centrifugal fluid pump of claim 1 further comprising a wall defining a fluid receiving chamber, the wall being connected to an upstream portion of the shroud and having an inlet opening positioned to align with the duct when the body is at least partially received within the bore, the inlet opening permitting the fluid to flow radially into the fluid receiving chamber from the duct.

6. The centrifugal fluid pump of claim 5 further comprising a seal arrangement disposed along an outer surface of the wall, the seal arrangement forming a seal between the inner surface of the bore and the outer surface of the wall when the body is at least partially received within the bore to inhibit the fluid that is received within the discharge port from flowing between the inner surface of the bore and the outer surface of the wall to the inlet opening.

7. The centrifugal fluid pump of claim 6 wherein the seal arrangement includes an o-ring seal.

8. The centrifugal fluid pump of claim 6 wherein the outer surface of the wall defines a groove to receive the seal arrangement.

9. The centrifugal fluid pump of claim 1 further comprising: a seal arrangement disposed along an outer surface of the shroud to form a seal between the outer surface of the shroud and the inner surface of the bore when the body is at least partially received within the bore; and a wall defining a fluid receiving chamber, the wall being connected to an upstream portion of the shroud, the wall defining an inlet opening positioned to align with the duct when the body is at least partially received within the bore, the inlet opening permitting fluid to flow radially into the fluid receiving chamber from the duct, the seal arrangement inhibiting the fluid that is received within the discharge port from flowing between the inner surface of the bore and the shroud to the inlet opening.

10. The centrifugal fluid pump of claim 1 wherein a portion of the impeller is disposed in sufficiently close association with an outer surface of the shroud to inhibit fluid from flowing between the impeller and the outer surface of the shroud as the impeller rotates.

11. A centrifugal fluid pump for circulating fluid through an engine, the engine having a bore to receive the pump and a fluid path to facilitate circulation of fluid through the engine, the engine further having a duct connected to the fluid path to direct fluid radially into the pump, the engine further having a block with a discharge port formed therein to receive fluid discharged from the pump, the discharge port being connected to the fluid path, the centrifugal fluid pump comprising: a housing configured to be at least partially received within the bore, the housing having a wall defining a fluid receiving chamber, the wall further defining an inlet to permit the radial flow of fluid into the fluid receiving chamber, the inlet aligning with the duct when the housing is at least partially received within the bore, the housing further having a shroud contiguous with the wall and disposed substantially transversely thereto, an inner surface of the shroud defining a portion of the fluid receiving chamber, the shroud having an outlet to permit the flow of fluid out of the chamber; and an impeller assembly supported on the housing and rotatably connected thereto, the impeller assembly including a bearing connected to the housing, a shaft rotatably supported on the bearing and an impeller connected to the shaft, the impeller being disposed substantially adjacent to an outer surface of the shroud proximate to the outlet, the impeller being configured to rotate with respect to the shroud and to draw fluid out of the outlet as the impeller rotates, the impeller further being disposed proximate to the discharge port when the housing is at least partially received within the bore, the impeller being configured to move fluid into the discharge port as the impeller rotates, the shroud remaining stationary with respect to the bore as the impeller rotates, and a periphery of the shroud being configured to engage an inner surface of the bore such that the periphery of the shroud and the inner surface of the bore cooperate to inhibit fluid from flowing upstream from the discharge port into the fluid receiving chamber.

12. The centrifugal fluid pump of claim 11 further comprising a seal arrangement disposed along the periphery of the shroud to form a seal between the periphery of the shroud and the inner surface of the bore when the housing is at least partially received within the bore to further inhibit the fluid that is received in the discharge port from flowing between the inner surface of the bore and the periphery of the shroud to a position upstream of the shroud.

13. The centrifugal fluid pump of claim 12 wherein the periphery of the shroud defines a groove to receive the seal arrangement.

14. The centrifugal fluid pump of claim 12 wherein the seal arrangement includes an o-ring seal.

15. The centrifugal fluid pump of claim 14 wherein the periphery of the shroud defines a groove to receive the o-ring.

16. The centrifugal fluid pump of claim 11 further comprising a seal arrangement disposed along an outer surface of the wall to form a seal between the outer surface of the wall and the inner surface of the bore when the housing is at least partially received within the bore to further inhibit the fluid that is received in the discharge port from flowing between the inner surface of the bore and the outer surface of the wall to the inlet.

17. The centrifugal fluid pump of claim 16 wherein the outer surface of the wall defines a groove to receive the seal arrangement.

18. The centrifugal fluid pump of claim 16 wherein the seal arrangement includes an o-ring seal.

19. The centrifugal fluid pump of claim 18 wherein the outer surface of the wall defines a groove to receive the o-ring seal.

20. The centrifugal fluid pump of claim 11 wherein a portion of the impeller is disposed in sufficiently close association with the outer surface of the shroud to inhibit fluid from flowing between the impeller and the outer surface of the shroud as the impeller rotates.

Description:

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a centrifugal fluid pump for circulating fluid through an engine.

2. Background Art

Internal combustion engines use coolant systems to prevent overheating. A pump may be used to circulate fluid through an internal combustion engine's cooling system to control the operational temperature of the engine. A centrifugal fluid pump is one type of pump that can be used to circulate fluid through an engine's cooling system. A centrifugal fluid pump is one that discharges fluid radially from the impeller. Engines configured to receive a centrifugal fluid pump frequently include a discharge port, for example, a volute, formed in the engine block to receive the radially discharged fluid and to direct such fluid along a coolant path through the engine. The path leads back to the pump and the cycle begins again. Some engines have a bore defined in the engine block disposed along the coolant path to receive the fluid pump. This allows the fluid pump to be inserted into the coolant path.

Some manufacturers make engines that are configured with a coolant path that directs fluid radially into a fluid pump. In such an arrangement, fluid flows radially into the centrifugal fluid pump from the engine's coolant path to a location that is upstream of an impeller. Fluid is then moved downstream into the discharge port by the impeller. One problem encountered with this type of pump is the tendency of some of the fluid to flow from an area in the discharge port that is down stream of the impeller directly to an area in the pump that is upstream of the impeller, thereby bypassing the coolant path. This recirculation reduces the efficiency of the pump because fluid never goes through the engine.

Some manufacturers of centrifugal fluid pumps have attempted to counter this problem by attaching a shroud to the impeller shaft that rotates with the impeller in an attempt to create a barrier between the upstream and the downstream areas of the centrifugal fluid pump. Such rotating shrouds, however, still permit the flow of some coolant to an upstream location after being discharged into the discharge port because of a gap between a periphery of the shroud and the inner surface of the bore that is needed to permit the shroud to rotate. This and other problems are addressed by the present invention.

SUMMARY OF THE INVENTION

In at least one embodiment, the present invention may include a centrifugal fluid pump for circulating fluids through an engine having a bore to receive the pump and a duct to direct fluid radially into the pump. The engine further has a block having a discharge port formed therein to receive fluid discharged from the pump. In such an arrangement, the centrifugal fluid pump comprises a body that is configured to be at least partially received within the bore, a shaft that is rotatably connected to the body, an impeller that is fixed to the shaft and rotatable therewith, the impeller being positioned to move fluid from the duct to the discharge port when the body is at least partially received within the bore, and a shroud supported on the body and positioned between the duct and the impeller when the body is at least partially received within the bore. The shroud may have an opening to permit the movement of the fluid from the duct to the impeller, and the shroud may be configured to engage an inner surface of the bore. The shroud remains stationary with respect to the bore as the shaft and the impeller rotate. In this arrangement, when the body is at least partially received within the bore, the shroud and the bore cooperate to inhibit fluid that is received in the discharge port from flowing between the inner surface of the bore and the shroud to a position upstream of the shroud.

There are many ways to implement the first embodiment. In at least one implementation, the centrifugal fluid pump further includes a seal arrangement disposed along an outer surface of the shroud to form a seal between the outer surface of the shroud and the inner surface of the bore when the body is at least partially received within the bore. This further inhibits the fluid that is received in the discharge port from flowing between the inner surface of the bore and the outer surface of the shroud to a position upstream of the shroud. In at least one variation of this implementation, the seal arrangement includes an O-ring seal. In at least another variation of this implementation, an outer surface of the shroud defines a groove to receive the seal arrangement.

In at least another implementation of the first embodiment, the centrifugal fluid pump further comprises a wall defining a fluid receiving chamber. The wall may be connected to an upstream portion of the shroud and may have an inlet opening that is positioned to align with the duct when the body is at least partially received within the bore. In this implementation, the inlet opening permits the fluid to flow radially into the fluid receiving chamber from the duct. In at least one variation of this implementation, the centrifugal fluid pump further comprises a seal arrangement disposed along an outer surface of the wall. The seal arrangement may form a seal between the inner surface of the bore and the outer surface of the wall when the body is at least partially received within the bore. In this arrangement, the seal inhibits the fluid that is received within the discharge port from flowing between the inner surface of the bore and the outer surface of the wall to the inlet opening. In a further variation of this implementation, the seal arrangement may include an O-ring seal. In a further variation of this implementation, the outer surface of the wall may define a groove to receive the seal arrangement.

In at least another implementation of the first embodiment, the centrifugal fluid pump may further comprise a seal arrangement that is disposed along an outer surface of the shroud to form a seal between the outer surface of the shroud and the inner surface of the bore when the housing is at least partially received within the bore. The centrifugal fluid pump may further comprise a wall defining a fluid receiving chamber. The wall may be connected to an upstream portion of the shroud and the wall may define an inlet opening that is positioned to align with the duct when the body is at least partially received within the bore. The inlet opening permits fluid to flow radially into the fluid receiving chamber from the duct. In this implementation, the seal arrangement inhibits the fluid that is received within the discharge port from flowing between the inner surface of the bore and the shroud to the inlet opening.

In at least another implementation of the first embodiment, a portion of the impeller is disposed in sufficiently close association with an outer surface of the shroud so as to inhibit fluid from flowing between the impeller and the outer surface of the shroud as the impeller rotates.

In at least a second embodiment, a centrifugal fluid pump for circulating fluid through an engine is provided. The engine has a bore to receive the pump and a fluid path to facilitate circulation of fluid through the engine. The engine further has a duct that is connected to the fluid path to direct fluid radially into the pump. The engine further has a block with a discharge port formed therein to receive the fluid that is discharged from the pump, the discharge port being connected to the fluid path. In this arrangement, the centrifugal fluid pump includes a housing that is configured to be at least partially received within the bore. The housing has a wall that defines a fluid receiving chamber. The wall further defines an inlet to permit the radial flow of fluid into the fluid receiving chamber, the inlet aligning with the duct when the housing is at least partially received within the bore. The housing further has a shroud that is contiguous with the wall and disposed substantially transversely thereto. An inner surface of the shroud may define a portion of the fluid receiving chamber. The shroud includes an outlet to permit the flow of fluid out of the chamber. The centrifugal fluid pump further comprises an impeller assembly that is supported on the housing and rotatably connected thereto. The impeller assembly includes a bearing that is connected to the housing, a shaft that is rotatably supported on the bearing, and an impeller that is connected to the shaft, the impeller being disposed substantially adjacent to an outer surface of the shroud proximate to the outlet. The impeller may be configured to rotate with respect to the shroud and to draw fluid out of the outlet as the impeller rotates. Further, the impeller may be disposed proximate to the discharge port when the housing is at least partially received within the bore, the impeller being configured to move fluid into the discharge port as the impeller rotates. In at least this embodiment, the shroud remains stationary with respect to the bore as the impeller rotates and a periphery of the shroud may be configured to engage an inner surface of the bore such that the periphery of the shroud and the inner surface of the bore cooperate to inhibit fluid from flowing upstream from the discharge port into the fluid receiving chamber.

There are many ways to implement the second embodiment. In least one implementation, the centrifugal fluid pump of the second embodiment further comprises a seal arrangement that is disposed along the periphery of the shroud to form a seal between the periphery of the shroud and the inner surface of the bore when the housing is at least partially received within the bore to further inhibit the fluid that is received in the discharge port from flowing between the inner surface of the bore and the periphery of the shroud to a position that is upstream of the shroud. In at least one variation of this implementation, the periphery of the shroud defines a groove to receive the seal arrangement. In at least another variation of this implementation, the seal arrangement includes an O-ring seal. In still another variation of this implementation, the periphery of the shroud defines a groove to receive the O-ring.

In another implementation of the second embodiment, the seal arrangement may be disposed along an outer surface of the wall to form a seal between the outer surface of the wall and the inner surface of the bore when the housing is at least partially received within the bore so as to further inhibit the fluid that is received in the discharge port from flowing between the inner surface of the bore and the outer surface of the wall to the inlet. In at least one variation of this implementation, the outer surface of the wall defines a groove to receive the seal arrangement. In at least another variation of this implementation, the seal arrangement includes an O-ring seal. In still another variation of this implementation, the outer surface of the wall defines a groove to receive the O-ring seal.

In at least another implementation of the second embodiment, a portion of the impeller is disposed in sufficiently close association with the outer surface of the shroud to inhibit fluid from flowing between the impeller and the outer surface of the shroud as the impeller rotates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a centrifugal fluid pump and an engine block;

FIG. 2 is a cutaway perspective view of the centrifugal fluid pump received within the engine block;

FIG. 3 is a fragmentary cross-sectional view of a portion of the engine block taken along the line 3-3 of FIG. 2;

FIG. 4 is a fragmentary cross-sectional view of a portion of the engine block and an embodiment of the centrifugal fluid pump received within a bore of the engine block taken along the line 3-3 of FIG. 2;

FIG. 5 is a fragmentary cross-sectional view of FIG. 4 depicting a second embodiment of the centrifugal fluid pump; and

FIG. 6 is a fragmentary cross-sectional view of FIG. 4 depicting a third embodiment of the centrifugal fluid pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

A centrifugal fluid pump 10 is shown in FIG. 1. Centrifugal fluid pump 10 is configured to be received within an engine 12, also shown in FIG. 1. Engine 12 includes a coolant path 14 configured to contain and circulate fluid through the engine and a heat exchanger (not shown) to maintain the engine at a desired temperature during engine operation. Engine 12 further includes a bore 16 that is configured to at least partially receive the centrifugal fluid pump 10. The bore 16 is disposed along coolant path 14. Coolant path 14 includes a duct 18 for directing coolant radially into the bore 16.

Centrifugal fluid pump 10 includes a body or housing 20 having a wall 22. In the embodiment illustrated in FIG. 1, the wall 22 defines a fluid receiving chamber 24 and an inlet 26 defined in the wall 22 to permit fluid to enter the fluid receiving chamber 24. Centrifugal fluid pump 10 is configured to be at least partially received within bore 16. When centrifugal fluid pump 10 is at least partially received within bore 16, inlet 26 aligns with duct 18 to allow fluid to flow radially from the coolant path 14 into the fluid receiving chamber 24.

In the illustrated embodiment, centrifugal fluid pump 10 includes a shaft 28 that is rotatably connected at one end to the body 20. At an opposite end, impeller 30 is mounted to shaft 28 and configured to rotate together with shaft 28 with respect to body 20. The rotation of impeller 30 causes fluid to move from the fluid receiving chamber 24 to the impeller 30. As the fluid engages impeller 30, it is discharged radially from impeller 30.

When impeller 30 is at least partially received within bore 16, impeller 30 is disposed proximate to discharge port 32. Discharge port 32 is configured to receive the fluid that is radially discharged from impeller 30 and to redirect it along coolant path 14. In the embodiment illustrated in FIGS. 1-6, discharge port 32 is a volute which has generally spiral configuration and which is adapted to convert the radial motion of fluid discharged from impeller 30 to linear motion. Discharge ports having other configurations may also be utilized to receive the fluid discharged from impeller 30.

As shown in FIG. 2, when centrifugal fluid pump 10 is at least partially received within bore 16, inlet 26 aligns with duct 18 to radially receive fluid into the fluid receiving chamber 24. Impeller 30 is positioned at least partially within the discharge port 32. Arranged in this manner, the coolant path 14, including the duct 18 and the discharge port 32 together with the centrifugal fluid pump 10, form a substantially closed path for the circulation of coolant through engine 12.

FIG. 3 is a fragmentary cross-sectional view of a portion of engine 12. The portion depicted is configured to receive a centrifugal fluid pump 10 within bore 16. As illustrated, duct 18 opens into bore 16 to allow for the radial introduction of fluid. A rear portion of bore 16 opens to discharge port 32 to receive fluid discharged from centrifugal fluid pump 10. Engine 12 includes holes 34 to permit centrifugal fluid pump 10 to be fastened to engine 12. The bore 16 includes an internal surface 36 that is configured to receive the centrifugal fluid pump 10 when centrifugal fluid pump 10 is inserted into the bore 16.

FIG. 4 depicts a first embodiment of centrifugal fluid pump 10 at least partially received within bore 16. As illustrated, centrifugal fluid pump 10 includes a body or housing 38, a bearing 40 connected to the body 38 and an impeller shaft 42 rotatably connected to the body 38 by bearing 40. A pulley hub 44 is connected to impeller shaft 42 and is configured for connection to a serpentine belt which may wrap around a portion of pulley hub 44 and which may cause pulley hub 44 to rotate as the serpentine belt moves. In other engines, an apparatus other than a serpentine belt may be used to rotate pulley hub 44. In other embodiments of the present invention, structures other than pulley hub 44 may be used to impart rotation to impeller shaft 42.

As illustrated, centrifugal fluid pump 10 may further include a flange 46. Flange 46 engages an outer surface of engine 12 to control the depth of insertion of the centrifugal fluid pump 10 into the bore 16. Flange 46 includes holes 48 which align with holes 34 when centrifugal fluid pump 10 is at least partially received within bore 16. Bolt 50 passes through hole 48 and is received in hole 34 and, through threaded engagement with an interior surface of hole 34, secures centrifugal fluid pump 10 to engine 12. In other embodiments, screws, other threaded fasteners or any other fastener effective to secure centrifugal fluid pump 10 to engine 12 may be used.

Body 38 further includes a body seal groove 52 to receive a body seal 54. Body seal 54 serves to fluidly seal the body 38 against an inner surface of bore 16 to prevent fluid from leaving the coolant path and leaking to an area outside of engine 12. In other embodiments, body seal 54 may be disposed on body 38 so as to contact engine 12 along an outer surface of engine 12 as opposed to an inner surface of bore 16. In at least one embodiment, body seal 54 may be a rubber o-ring. In other embodiments, body seal 54 may be any type of seal effective to prevent fluid from leaving the coolant path and leaking to an area outside of engine 12.

As illustrated in FIG. 4, centrifugal fluid pump 10 includes a wall 22 connected to the body 38. The wall 22 defines the fluid receiving chamber 24. Inlet 26 is defined in wall 22 and, as illustrated in FIG. 4, aligned with duct 18 when centrifugal fluid pump 10 is at least partially received within bore 16. An outer surface of wall 22 engages an inner surface of bore 16 when centrifugal fluid pump 10 is at least partially received within bore 16. In some embodiments, such engagement may be in the form of an interference fit. In other embodiments, such engagement may take the form of a close association between the two surfaces, meaning that the two surfaces are disposed very close to one another. In at least some embodiments, once centrifugal fluid pump 10 is at least partially received within bore 16, and once centrifugal fluid pump 10 is fastened to engine 12, wall 22 remains stationary with respect to the inner surface of bore 16. In other embodiments, centrifugal fluid pump 10 may have neither wall 22 nor fluid receiving chamber 24.

The centrifugal fluid pump 10 illustrated in FIG. 4 further includes a shroud 60 connected to wall 22. Through this connection to wall 22, shroud 60 remains stationary with respect to body 38. In embodiments lacking a wall 22, shroud 60 may be connected to body 38 in a non-rotational fashion through other means such as posts, bands, beams, struts, braces, or any other member effective to attach shroud 60 to body 38 so that shroud 60 does not rotate. In the illustrated embodiment, an inner surface of shroud 60 defines a portion of fluid receiving chamber 24. In other embodiments, the shroud 60 may be separate from the structure defining fluid receiving chamber 24. Shroud 60 includes an opening or outlet 62 to permit fluid to flow out of the fluid receiving chamber 24. As illustrated, impeller shaft 42 extends through the fluid receiving chamber 24, protrudes through opening 62 and is disposed within the discharge port 32.

A periphery 64 of shroud 60 is illustrated in close association with the inner surface of bore 16. In some embodiments, the periphery 64 may be in contact with the inner surface of the bore at one or more locations around periphery 64. In other embodiments, the entire periphery 64 may be in contact with an inner surface of the bore 16. In still other embodiments, portions of the periphery 64 may provide an interference fit with the inner surface of the bore 16. In still other embodiments, the entire periphery 64 may provide an interference fit with the inner surface of the bore 16.

Impeller 66 is connected to impeller shaft 42 and is configured to rotate together with impeller shaft 42. Impeller 66 includes vanes 68 which, in the embodiment illustrated in FIG. 4, are disposed in close association with an outer surface of shroud 60. In some embodiments, vanes 68 may be disposed so as to provide a sliding contact with the outer surface of shroud 60.

When a serpentine belt or other source of rotation is applied to pulley hub 44, impeller shaft 42 rotates with respect to body 38 causing impeller 66 to rotate. When impeller 66 rotates, it pushes fluid radially away from impeller 66 into discharge port 32. Discharge port 32 directs the moving fluid into the coolant path 14 which then circulates the fluid through engine 12 to duct 18 where the fluid passes through inlet 26 and enters fluid receiving chamber 24. From the fluid receiving chamber 24, the fluid is moved through opening 62 back to impeller 66. The path of the fluid is indicated in FIG. 4 with arrows showing the direction of fluid travel.

The efficiency with which centrifugal fluid pump 10 moves fluid through engine 12 could be adversely impacted if fluid received within the discharge port 32 were to leak back to inlet 26 instead of entering the coolant path 14. By providing a shroud 60 that remains stationary, a very close association between the periphery 64 and an inner surface of the bore 16 can be provided so as to inhibit the fluid from leaking between the periphery 64 and an inner surface of the bore 16 back to inlet 26.

The efficiency of centrifugal pump 10 can be further improved by disposing vanes 68 in close association with an outer surface of shroud 60. A close association can inhibit fluid from flowing between these components. Fluid that flows between vanes 68 and an outer surface of shroud 60 does not enter the coolant path 14, but instead recirculates through impeller 66. The narrower the gap is between vanes 68 and the outer surface of shroud 60, the less fluid will recirculate, and the greater will be the efficiency of the centrifugal fluid pump 10.

To further improve the efficiency of the centrifugal fluid pump 10, an additional seal can be used. FIG. 5 illustrates one embodiment of a centrifugal fluid pump 10 utilizing an additional seal to further inhibit fluid from leaking between the periphery 64 of shroud 60 and an inner surface of bore 16. In the illustrated embodiment, an O-ring seal 70 is received within O-ring seal groove 72, both of which are disposed along the periphery 64 of the shroud 60. As illustrated, O-ring 70 provides an interference fit against an inner surface of the bore 60. Disposed around the entire periphery 64 of shroud 60, O-ring seal 70 inhibits fluid from leaking from the discharge port 32 to inlet 26. Seals other than O-ring seals may also be utilized. In still other embodiments, the seal arrangement may be disposed elsewhere on the centrifugal fluid pump 10. For instance, as illustrated in FIG. 6, an O-ring seal 74 is disposed within an O-ring seal groove 76 that is disposed along an outer surface of wall 22. In the arrangement illustrated in FIG. 6, any fluid that leaks between periphery 64 of shroud 60 and an inner surface of bore 16 will be inhibited from reaching inlet 26 by O-ring seal 74.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.