Vane Pump Assembly

Abstract

The vane pump has a housing with an inner wall which surrounds an inner chamber and has circumferentially spaced inlet ports and circumferentially spaced outlet ports. The vane pump assembly further includes a rotor which is rotatably disposed in the inner chamber of the housing and has a circular outer surface and presents at least two passages which are spaced from a center axis of the rotor. A curved or rocker vane is disposed in each of the passages, and each of the curved or rocker vanes extends between opposite vane ends that project past the circular outer surface of the rotor for sealing against the inner wall. The curved or rocker vanes are articulatable back and forth within the passages to maintain the vane ends in sealing engagement with the inner wall of the housing as the rotor rotates relative to the housing within the inner chamber.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related generally to rotary vane pump assemblies.

2. Related Art

In general, rotary vane pump assemblies are positive displacement pumps that include one or more vanes that are mounted to a rotor which is rotatable within a housing having an inner wall defining an open chamber. A pressure differential is applied across the vane, which causes the rotor to rotate within the open chamber of the housing. The rotor is coupled with an output shaft which may be attached to any suitable machine including, for example, an electric generator. During operation of such vane pump assemblies, it is important to maintain a fluid-tight seal between the vane and the inner wall of the housing in order to optimize efficiency and maximize power output.

One approach to maintaining the fluid-tight seal between the vane and the housing is to use springs to bias the vane against the inner wall of the housing. Rotary vane pumps that use this approach generally include two or more vanes, and a spring is disposed between the rotor and each vane to bias the respective vane in a radially outward direction and against this housing. The biasing forces exerted by the springs maintain the vanes in continuous contact with the housing through a full 360 degrees of rotation of the rotor within the open chamber of the housing.

Another approach to maintaining the fluid-tight seal between the vane and the housing is to provide open chamber with a non-circular shaped cross-section. The rotor is centered within the non-circular open chamber, and a vane extends through the rotor to engage at either end with an inner wall of the open chamber. The noncircularly shaped cross-section of the open chamber guides the vane through a reciprocating motion back and forth across the rotor to maintain both ends of the vane in contact with the inner wall to establish the fluid tight seals.

In some rotary vane pumps it is additionally important for the rotor to seal against the inner wall. In general this is accomplished by manufacturing the rotor and housing under tight tolerances in order to achieve a tight fit between the rotor and the inner wall of the housing. However, it is often costly as expensive and time consuming manufacturing and/or machining processes must be employed to achieve such tight tolerances.

SUMMARY OF THE INVENTION AND ADVANTAGES

One aspect of the present invention is related to a vane pump assembly with a housing. The housing has an inner wall which surrounds a non-circular inner chamber and has at least two circumferentially spaced fluid inlet ports for conveying a fluid into the inner chamber and at least two circumferentially spaced fluid outlet ports for conveying the fluid out of the inner chamber. The vane pump assembly further includes a rotor which is rotatably disposed in the inner chamber of the housing and has a circular outer surface and presents at least two passages which are spaced from a center axis of the rotor. A curved or rocker vane is disposed in each of the passages, and each of the curved or rocker vanes extends between opposite vane ends that project past the circular outer surface of the rotor for sealing against the inner wall. The curved or rocker vanes are articulatable back and forth within the passages to maintain the vane ends in sealing engagement with the inner wall of the housing as the rotor rotates relative to the housing within the inner chamber.

The curved or rocker vanes have been found to establish a more reliable and durable seal as compared to other styles of vanes in vane pumps. The curved or rocker vanes also allow a shaft to extend through the length of the rotor.

According to another aspect of the present invention, the passages are curved, and the vanes are curved and are slidable within the curved passages for articulating back and forth within the curved passages.

According to yet another aspect of the present invention, the vanes are pivotable about a pivot for articulating back and forth within the passages.

According to still another aspect of the present invention, the non-circular inner chamber of the housing is elliptical in shape.

According to a further aspect of the present invention, the at least two passages in the rotor is exactly two passages.

According to yet a further aspect of the present invention, each of the vanes includes a vane body and each of the vane ends includes at least one primary roller received in a U-shaped groove of the vane body for rolling along the inner wall of the housing as the rotor rotates relative to the housing.

According to still a further aspect of the present invention, the inner wall of the housing has at least one thin walled portion between one of the fluid inlet ports and one of the fluid outlet ports and further including an adjustable biaser that applies a force against an opposite side of the thin walled portion from the rotor to seal the thin walled portion against the rotor.

According to another aspect of the present invention, the biaser includes at least one bar which is received in a passage of the housing and includes at least one adjustment screw that engages the bar to move the bar and adjust the force applied by the bar against the thin walled portion of the housing.

Another aspect of the present invention is related to a vane pump assembly which includes an inner wall that surrounds an inner chamber. The housing further includes at least two circumferentially spaced fluid inlet ports for conveying a fluid into the inner chamber and at least two circumferentially spaced fluid outlet ports for conveying the fluid out of the inner chamber. A rotor is rotatably disposed in the housing and has an outer surface which contacts or nearly contacts the inner wall of the housing in at least one location between one of the fluid inlet ports and one of the fluid outlet ports. At least one vane is at least partially received within a passage of the rotor and extends outwardly therefrom for establishing a seal against the inner wall of the housing. The inner wall of the housing includes at least one thin walled portion in at least one location where the rotor contacts or nearly contacts the inner wall. A biaser is disposed on an opposite side of the thin walled portion from the rotor and applies a force against the thin walled portion to establish a seal between the thin walled portion of the inner wall and the rotor. Advantageously, the biaser allows for an improved seal between the inner wall of the housing and the rotor to prevent air from flowing directly from the air inlet to the air outlet, which would reduce the efficiency of the vane pump assembly.

According to yet another aspect of the present invention, the biaser further includes at least one adjustment screw which engages the bar for adjusting the force applied by the biaser against the thin walled portion of the inner wall of the housing.

According to still another aspect of the present invention, the at least one vane is further defined as at least two vanes and wherein each of the vanes extends between a pair of vane ends.

According to a further aspect of the present invention, the vanes are curved vanes that are slidable within the respective passages for sliding back and forth within the passages to maintain the vane ends in sealing contact with the inner wall of the housing.

According to yet a further aspect of the present invention, the vanes are rocker vanes.

Yet another aspect of the present invention is related to a vane pump assembly which includes a housing with an inner wall. The inner wall surrounds an elliptically shaped inner chamber. The housing includes a pair of circumferentially spaced fluid inlet ports for conveying a fluid into the inner chamber and a pair of circumferentially spaced fluid outlet ports for conveying the fluid out of the inner chamber. The inner wall has a thin walled portion between one of the fluid inlet ports and one of the fluid outlet ports. A rotor is rotatably disposed in the inner chamber of the housing. The rotor has a circular outer surface and at least two passages which are spaced from a center axis of the rotor. The rotor is in contact or nearly in contact with the thin walled portion of the inner wall of the housing. A biaser is disposed on an opposite side of the thin walled portion of the inner wall from the rotor and applies a force against the thin walled portion to seal the thin walled portion of the inner wall against the rotor. The biaser includes a bar which is disposed in a passage of the housing. The biaser additionally includes at least one adjustable screw which is in engagement with the bar for adjusting the force applied by the bar against the thin walled portion of the inner wall of the housing. A curved or rocker vane is disposed in each of the passages, and each of the curved or rocker vanes extends between opposite vane ends that project past the circular outer surface of the rotor for sealing against the inner wall. The curved or rocker vanes are articulatable back and forth within the passages to maintain the vane ends in sealing engagement with the inner wall of the housing as the rotor rotates relative to the housing within the inner chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a cross-sectional view of a first exemplary embodiment of a vane pump assembly constructed according to one aspect of the present invention;

FIG. 2 is a perspective and elevational view of a rotor and a plurality of vanes from the vane pump assembly of FIG. 1;

FIG. 3 is a perspective and elevation view of the vanes of FIG. 2;

FIG. 4 is a perspective view showing the installation of a pair of bars into the vane pump assembly of FIG. 1;

FIG. 5 is a perspective and sectional view of the vane pump assembly of FIG. 1;

FIG. 6 is a perspective and elevation view of an alternate embodiment of the vanes for the vane pump assembly of FIG. 1;

FIG. 7 is a cross-sectional view of an alternate embodiment of the vane pump assembly; and

FIG. 8 is a perspective and elevation view of an alternate embodiment of the vanes for use in the vane pump assembly of FIG. 7.

DETAILED DESCRIPTION OF THE ENABLING EMBODIMENTS

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a first exemplary embodiment of a vane pump assembly 20 is generally shown in FIG. 1. As shown, the exemplary vane pump assembly 20 includes a housing 22 which is annularly disposed about an axis A and has an inner wall 24 that presents an axially extending open or inner chamber 26 which is non-circular in shape. The open chamber 26 has an upper portion 28 and a lower portion 30. In this exemplary embodiment, the non-circular shape of the open chamber 26 is elliptical.

The housing 22 defines a plurality of ports 32, 34 which are spaced circumferentially from one another and extend through the inner wall 24 and into the open chamber 26. In the exemplary embodiment shown in FIG. 1, the ports 32, 34 include two fluid inlet ports 32 for conveying a fluid into the open chamber 26 and two fluid outlet ports 34 for dispensing the fluid out of the open chamber 26. The fluid inlet ports 32 are spaced circumferentially from the fluid outlet ports 34. One fluid inlet port 32 and one fluid outlet port 34 are each disposed adjacent to the upper portion 28 and the other fluid inlet port 32 and fluid outlet port 34 are each disposed adjacent to the lower portion 30 of the open chamber 26. Although two of each type of port is utilized in the exemplary embodiment, it should be appreciated that any suitable number of ports 32, 34 may be included in the housing 22.

The vane pump assembly 20 also includes a rotor 36 which has a circle shaped cross-section and an outer surface 38. The rotor 36 is rotatably disposed about the central axis A in the open chamber 26 of the housing 22 for allowing the rotor 36 to rotate relative to the housing 22 during operation of the vane pump assembly 20. Referring additionally to FIG. 2, the rotor 36 presents a plurality of through-passages 40 that extend across the rotor 36 and axially along the rotor 36. The rotor 36 also has an opening 42 which is disposed centrally and extends axially through the rotor 36. The opening 42 presents a keyway 44 which has a rectangularly shaped cross-section. The rotor 36 also presents a pair of channels 48 that oppose from one another and extend circumferentially from each of the through-passages 40. Vane seals 50 are disposed in the channels 48 and contact the vanes 52 for preventing movement of the fluid between the vane 52 and the through-passages 40 of the rotor 36. The rotor 36 may be sealed with the housing 22 at either axial end of the rotor 36 (or both ends) with at least one axial seal (not shown) disposed within an arc shaped track on the opposite axial ends of the rotor 36. The axial seals may also be biased axially by, for example, springs. However, it should be understood that other sealing arrangements could be used instead.

As shown in FIG. 2, the exemplary rotor 36 of the vane pump assembly 20 is formed from two parts which are made separately and are subsequently joined together in an axial direction. This two part design could help facilitate the assembly of the vanes 52 with the rotor 36. The rotor 36 could instead be formed as one integral piece through an extrusion process followed by machining the through-passages 40 therein. However, any suitable manufacturing process or combination of processes may be employed to manufacture the rotor 36.

The vane pump assembly 20 further includes a shaft 54 which extends axially through the opening 42 of the rotor 36 and past at least one axial side of the housing 22. The shaft 54 includes at least one key 56 (FIG. 1) which extends radially from the shaft 54 and into the keyway 44 to fix the shaft 54 to the rotor 36 such that the shaft and rotor 36 rotate with one another. If the vane pump assembly 20 is operating to compress a fluid coming in through the fluid inlet ports 32 and exiting through the fluid outlet ports 34, then the shaft 54 functions as an input which may be coupled to any suitable power device capable of providing rotary motion to the shaft 54 and the rotor 36. The power device could be, for example, an electric motor or an internal combustion engine. Alternatively, if the vane pump assembly 20 is operating as an engine converting the energy of expanding fluids coming in through the fluid input ports 32, 34 and exiting through the fluid outlet ports 34 into rotational energy imparted to the shaft 54, the shaft 54 functions as an output. As an output, the shaft 54 may be coupled to any desirable power-receiving device, e.g. an electrical generator or the drivetrain of a vehicle. In this configuration the vane pump assembly 20 may be powered by any suitable source of pressurized fluid including, for example, steam. For example, the vane pump assembly 20 could be disposed in a Rankine style heat engine to provide the pressurized steam to drive rotation of the rotor 36 in the vane pump assembly 20.

In the exemplary embodiment, a pair of end plates 58 are disposed at opposite ends of the rotor 36 and are fixed to the shaft 54 for preventing axial movement of the vanes 52 and for transferring torque to the rotor 36 from the shaft 54 and vice versa depending on the operating mode of the vane pump assembly 20. A plurality of bolts 60 extend through the bores 46 of the rotor 36 and between the end plates 58 for interconnecting the end plates 58 with the rotor 36. The end plates 58 of the exemplary embodiment further include an indentation (not shown) to accept an O-ring to seal the end plate 58 against the rotor 36.

A plurality of vanes 52 are slidably disposed in the through-passages 40 of the rotor 36 and are moveable relative to the rotor 36. The vanes 52 extend between opposite vane ends, and each vane 52 has a front 62 and a back 64 (shown in FIG. 1). In the exemplary embodiment, the vanes 52 each have a second length between the vane ends that is greater than the first length of the through-passages 40. This causes the vane ends to project radially past the outer surface 38 of the rotor 36. During operation of the vane pump assembly 20, each vane 52 moves or articulates back 64 and forth in the through-passage 40 and such that the vane ends remain against the inner wall 24 of the housing 22 during an entire three-hundred and sixty degrees (360°) of rotation relative to the rotor 36.

The housing 22, rotor 36 and vane 52 of the vane pump assembly 20 may be made of a range of different materials such as, for example, various types of ceramics, thermoplastics or metals. These components may also be formed and assembled together through any suitable process or combination of processes.

As best illustrated in FIGS. 1-3, the vanes 52 of the first exemplary embodiment each have an arc shaped or curved cross-sectional shapes and are slidably disposed in curved through-passages 40 of the rotor 36 for articulating back 64 and forth in the through-passage 40 to seal against the inner wall 24 of the housing 22 during operation of the vane pump assembly 20. Each vane 52 moves along a sliding arch 66 with a constant radius. That is, each vane 52 rotates about a point which is located outside of the rotor 36 such that each vane 52 intersects the outer surface 38 of the rotor 36 at two locations that are approximately 90 degrees apart from one another. Because the vanes 52 have arc shaped cross-sections, the shaft 54 does not have to be offset from the center of the rotor 36 as may be necessary for vane pumps with one or more vanes that have straight cross-sectional shapes.

The vanes 52 of the exemplary embodiment also each include vane bodies which at the vane ends present grooves 68 that are U-shaped and extend axially from the front 62 to the back 64 of the vanes 52. At least one primary roller 70 with a cylindrical shape is disposed in each of the grooves 68 at the vane ends. In operation of the vane pump assembly 20, centrifugal force from the rotation of the rotor 36 biases the vane 52 such that the vane ends are sealed against the inner wall 24 of the housing 22. The centrifugal force maintains the rollers 70 in rolling contact with the inner wall 24 of the housing 22 while the vane 52 articulates back 64 and forth through the through-passage 40 of the rotor 36. The outer surface 38 of the rotor 36, inner wall 24, and primary rollers 70 define a crescent shaped pumping chamber 72.

In the exemplary embodiment, the rotor 36 rotates counterclockwise. The fluid inlet ports 32 and fluid outlet ports 34 alternate in a counterclockwise direction to correspond with the counterclockwise rotation of the rotor 36. In other words, as the rotor 36 turns in a counterclockwise direction, the vanes 52 cause fluid to move through each pumping chamber 72 from each fluid inlet port 32 toward and into the respective fluid outlet port 34.

At any given time during operation, at least one primary roller 70 of the vane 52 is in contact with and sealed against the inner wall 24 of the housing 22 through at least part of one complete revolution of the rotor 36 within the open chamber 26 of the housing 22. This establishes a gas tight seal capable of maintaining a pressure difference across the vane 52 within the pumping chamber 72 of the housing 22. In other words, the pressure of the fluid on one side of the vane 52 in the pumping chamber 72 is greater than the pressure of the fluid on the other side of the vane 52. This pressure difference drives rotation of the vane 52 and the rotor 36 when the vane pump assembly 20 is operating as an engine. The fluid outlet port 34 of the exemplary embodiment additionally includes a flap or Reed valve (not shown) that resiliently deflects to close the fluid outlet port 34 as the vane 52 passes while leaving the input ports 32 open. This flap or Reed valve helps reduce the noise and lost energy resulting from operation of the vane pump assembly 20 that may result from a transition from high pressure into low pressure that occurs when a vane 52 passes a fluid outlet valve and the fluid exits the open chamber 26.

Referring now to FIG. 3, the vanes 52 of the exemplary embodiment each include a first piece 76 and a second piece 78. Both the first piece 76 and the second piece 78 include a base 80 and three legs 82 extending in a parallel relationship with one another transversely away from the base 80. The legs 82 of the two pieces 76, 78 interleave with each other. Each leg 82 defines two orifices that align with the orifices of adjacent legs 82 when interleaved and extends axially through the first piece 76 and the second piece 78 of the vane 52. The base 80 and the legs 82 of the vane 52 also define a recess 84 when the first piece 76 and the second piece 78 are interleaved. The recess 84 extends along the leg 82 of the vane 52 and one is disposed at the front 62 of the vane 52 and another is disposed at the back 64 of the vane 52. A pin 86 extends axially through each of the orifices and into each of the recesses 84 to interconnect the first piece 76 and the second piece 78 with one another. This two-piece configuration of the vane 52 is particularly advantageous because it allows for simpler installation of the vane 52 into the through-passages 40 of the rotor 36. Specifically, the first piece 76 of the vane 52 may be inserted into the through-passages 40 from one direction, and the second piece 78 of the vane 52 may be inserted into the through-passages 40 from an opposite direction. The pieces 76, 78 may then be joined together within the rotor 36. However, depending on the configuration of the rotor 36, the vane 52 may take a range of shapes and configurations.

A plurality of vane articulation rollers 88 are disposed in each recess 84 of the vane 52 and are rotatable about the pins 86 for guiding articulation of the vane 52 in the through-passage 40 during operation of the vane pump assembly 20. In the exemplary embodiment, the vane articulation rollers 88 are sized so that they only engage one side of the through-passage 40 at a time, rather than being in engagement with both sides (i.e., the vane articulation rollers 88 only grip one side at a time). This helps facilitate movement of the vanes 52 in the through-passages 40. Although the vane articulation rollers 88 are disposed in the recess 84 of the vanes 52 in the exemplary embodiment, it should be appreciated that the vane articulation rollers 88 may be arranged in various other ways. For example, as shown in FIG. 6, the vane articulation rollers 88 could also be employed on both sides of the vanes 52 to facilitate their movement through the rotor 36. Other embodiments may not include any vane articulation rollers 88.

Referring back to FIG. 1, as shown, the rotor 36 comes into contact or near contact with a thin walled portion of the inner wall 26 of the housing 22 in two locations which are each located between adjacent ones of the fluid inlet ports 32 and the fluid outlet ports 34. In order to allow for adjustment of the dimensions of open chamber 26 of the exemplary embodiment, the housing 22 defines further defines two passageways 90, one extending axially along the upper portion 28 and another along the lower portion 30 of the open chamber 26. An adjustable biaser including a bar 92 is disposed in each of the passageways 90 on an opposite side of the thin walled portion from the rotor 36. The biaser further includes a pair of adjustment screws 94 which are each threadedly engaged with cavities of the housing 22 and extend through the housing 22 into the passageway 90 to engage the bars 92. The adjustment screws 94 engage the bar 92 for moving the bar 92 and deforming the inner wall 24 of the housing 22 to contact the peripheral edge 38 of the rotor 36 in response to the adjustment screws 94 being turned relative to the housing 22. This ability to adjust the dimensions of open chamber 26 of the housing 22 advantageously accounts for manufacturing tolerances by minimizing any fluid leaks directly from the fluid inlet ports 32 to the fluid outlet ports 34.

Referring now to FIG. 6, a second exemplary embodiment of the vanes 152 is generally shown with like numerals, separated by a prefix of “1” indicating corresponding parts with the above-described embodiment. The second embodiment is distinguished from the first embodiment by the inclusion of slide elements 74 disposed in grooves 168 in the vane bodies. Additionally, springs (not shown) or compressed gasses for example, may be disposed between the slide elements 174 and the vane bodies to maintain the slide elements 74 in contact with the inner wall 24 (shown in FIG. 1) of the housing 22 (shown in FIG. 1) during operation of the vane pump assembly 20 (shown in FIG. 1).

Referring now to FIG. 7, wherein like numerals separated by a prefix of “2” indicate corresponding parts with the above-described embodiments, a third exemplary embodiment of the vane pump assembly 220 is generally shown. The third exemplary embodiment is distinguished from the first exemplary embodiment in that the vanes 252 are each rocker vanes with W-shaped cross-sections and with a pair of lever arms 96 that extend outwardly from respective fulcrums 98 that connect first vane segments 100 and second vane segments 102. The rotor 236 further defines a furrow 104 which is open to the through-passage 240 and is coupled to the fulcrum 98 for engaging the fulcrum 98 of the vane 252 to allow the first vane segment 100 and the second vane segment 102 to alternately slide into and out of the through-passage 40 in response to the vane 252 pivoting about the fulcrum 98 relative to the rotor 36.

Referring now to FIG. 8, another exemplary embodiment of the vanes 352 is generally shown with like numerals, separated by a prefix of “3” indicating corresponding parts with the vanes 252 of the embodiment shown in FIG. 7. In this embodiment, the fulcrum 398 of each vane 352 presents an aperture 106 that extends axially through the vane 352 and a rod (not shown) extends through the aperture 106 and attaches to the rotor 236 (shown in FIG. 7) for allowing the vane 352 to pivot about the rod relative to the rotor 236.

In all of the above-discussed embodiments, all surfaces that slide against one another may also include a coating of coating used to reduce friction such as, but not limited to Polytetrafluoroethylene (PTFE). For example, with reference to FIG. 1, the thin walled portion of the inner wall 24 of the housing 22 which comes in contact with the outer surface 38 of the rotor 36 may include a PTFE coating and the peripheral edge 38 of the rotor 36 itself may also be coated to reduce friction and extend the life of these parts. As another example, through-passages 40 may also include a coating such as PTFE to help reduce friction as the vanes 52 move therein.

The vane pump assembly 20 may be used individually or together with other vane pump assemblies 20. More specifically, a plurality of the vane pump assemblies 20 can be arranged so that the shaft 54 of each vane pump assembly 20 is mechanically connected to an adjoining vane pump assembly 20, wherein the shafts 54 rotate in unison. However, each vane pump assembly 20 may be coupled to other vane pump assemblies 20 by, for example, a gearbox. Additionally, fluid inlet ports 32 and fluid outlet ports 34 of one vane pump assembly 20 may be interconnected to ports 32, 34 of another vane pump assembly 20.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims.

Claims

1. A vane pump assembly, comprising: a housing with an inner wall which surrounds a non-circular inner chamber and at least two circumferentially spaced fluid inlet ports for conveying a fluid into said inner chamber and at least two circumferentially spaced fluid outlet ports for conveying the fluid out of said inner chamber;a rotor rotatably disposed in said inner chamber of said housing and having a circular outer surface and presenting at least two passages which are spaced from a center axis of said rotor;a curved or rocker vane disposed in each of said passages, each of said curved or rocker vanes extending between opposite vane ends that project past said circular outer surface of said rotor for sealing against said inner wall; andsaid curved or rocker vanes being articulatable back and forth within said passages to maintain said vane ends in sealing engagement with said inner wall of said housing as said rotor rotates relative to said housing within said inner chamber.

2. The vane pump assembly as set forth in claim 1 wherein said passages are curved and said vanes are curved and are slidable within said curved passages for articulating back and forth within said curved passages.

3. The vane pump assembly as set forth in claim 1 wherein said vanes are pivotable about a pivot for articulating back and forth within said passages.

4. The vane pump assembly as set forth in claim 1 wherein said non-circular inner chamber is elliptical in shape.

5. The vane pump assembly as set forth in claim 1 wherein said at least two passages is exactly two passages.

6. The vane pump assembly as set forth in claim 1 wherein each of said vanes includes a vane body and wherein each of said vane ends includes at least one primary roller received in a U-shaped groove of said vane body for rolling along said inner wall of said housing as said rotor rotates relative to said housing.

7. The vane pump assembly as set forth in claim 1 wherein said inner wall of said housing has at least one thin walled portion between one of said fluid inlet ports and one of said fluid outlet ports and further including an adjustable biaser that applies a force against an opposite side of said thin walled portion from said rotor to seal said thin walled portion against said rotor.

8. The vane pump assembly as set forth in claim 7 wherein said biaser includes at least one bar which is received in a passage of said housing and includes at least one adjustment screw which engages said bar to move said bar and adjust the force applied by said bar against said thin walled portion of said housing.

9. A vane pump assembly, comprising: a housing with an inner wall which surrounds an inner chamber and at least two circumferentially spaced fluid inlet ports for conveying a fluid into said inner chamber and at least two circumferentially spaced fluid outlet ports for conveying the fluid out of said inner chamber;a rotor rotatably disposed in said housing and having an outer surface which contacts or nearly contacts said inner wall of said housing in at least one location between one of said fluid inlet ports and one of said fluid outlet ports;at least one vane at least partially received within a passage of said rotor and extending outwardly therefrom for establishing a seal against said inner wall of said housing;said inner wall of said housing including a thin walled portion in at least one location where said rotor contacts or nearly contacts said inner wall; anda biaser disposed on an opposite side of said thin walled portion from said rotor and applying a force against said thin walled portion to establish a seal between said thin walled portion of said inner wall and said rotor.

10. The vane pump assembly as set forth in claim 9 wherein said biaser includes a bar received in a passage of said housing on an opposite side of said thin walled portion of said inner wall from said rotor.

11. The vane pump assembly as set forth in claim 10 wherein said biaser further includes at least one adjustment screw which engages said bar for adjusting said force applied by said biaser against said thin walled portion of said inner wall of said housing.

12. The vane pump assembly as set forth in claim 9 wherein said at least one vane is further defined as at least two vanes and wherein each of said vanes extends between a pair of vane ends.

13. The vane pump assembly as set forth in claim 12 wherein said vanes are curved vanes that are slidable within said respective passages for sliding back and forth within said passages to maintain said vane ends in sealing contact with said inner wall of said housing.

14. The vane pump assembly as set forth in claim 12 wherein said vanes are rocker vanes.

15. A vane pump assembly, comprising: a housing with an inner wall which surrounds an elliptically shaped inner chamber and a pair of circumferentially spaced fluid inlet ports for conveying a fluid into said inner chamber and a pair of circumferentially spaced fluid outlet ports for conveying the fluid out of said inner chamber;said inner wall of said housing including a thin walled portion between one of said fluid inlet ports and one of said fluid outlet ports;a rotor rotatably disposed in said inner chamber of said housing and having a circular outer surface and presenting at least two passages which are spaced from a center axis of said rotor;said rotor being in contact or nearly in contact with said thin walled portion of said inner wall of said housing;a biaser disposed on an opposite side of said thin walled portion of said inner wall from said rotor and applying a force against said thin walled portion to seal said thin walled portion of said inner wall against said rotor, said biaser including a bar disposed in a passage of said housing, and said biaser including at least one adjustable screw in engagement with said bar for adjusting the force applied by said bar against said thin walled portion of said inner wall of said housing;a curved or rocker vane disposed in each of said passages, each of said curved or rocker vanes extending between opposite vane ends that project past said circular outer surface of said rotor for sealing against said inner wall; andsaid curved or rocker vanes being articulatable back and forth within said passages to maintain said vane ends in sealing engagement with said inner wall of said housing as said rotor rotates relative to said housing within said inner chamber.