Fluid pump with flow impedance member

1. A fluid pump comprising:

an inlet for introducing fluid into said fluid pump;

an outlet for discharging said fluid from said fluid pump;

a motor having an armature which rotates about an axis such that said armature is supported at one end by a first bearing and at a second end by a second bearing, said motor also having a stator which circumferentially surrounds said armature such that a fluid passage is defined radially between said armature and said stator through which said fluid flows from said inlet to said outlet;

a pumping arrangement which is rotated by said armature and which pumps said fluid from said inlet to said outlet; and

a flow impedance member extending axially in said fluid passage which impedes circumferential flow of said fluid within said fluid passage, thereby generating a pressure gradient circumferentially within said fluid passage which applies a lateral force to said armature;

wherein said fluid pump further comprises an axial flow separator located within said fluid passage which impedes axial flow of said fluid within said fluid passage, wherein said axial flow separator is located between said flow impedance member and said outlet;

wherein said axial flow separator is annular in shape and includes an axial flow separator flow aperture extending axially therethrough which provides fluid communication from said fluid passage to said outlet.

2. A fluid pump as in claim 1 wherein said axial flow separator flow aperture is not centered about said axis.

3. A fluid pump comprising:

an inlet for introducing fluid into said fluid pump;

an outlet for discharging said fluid from said fluid pump;

a motor having an armature which rotates about an axis such that said armature is supported at one end by a first bearing and at a second end by a second bearing, said motor also having a stator which circumferentially surrounds said armature such that a fluid passage is defined radially between said armature and said stator through which said fluid flows from said inlet to said outlet;

a pumping arrangement which is rotated by said armature and which pumps said fluid from said inlet to said outlet;

a flow impedance member extending axially in said fluid passage which impedes circumferential flow of said fluid within said fluid passage, thereby generating a pressure gradient circumferentially within said fluid passage which applies a lateral force to said armature;

wherein said flow impedance member is a lower flow impedance member which impedes circumferential flow of said fluid within said fluid passage, thereby generating a first pressure gradient circumferentially within said fluid passage which applies a lower lateral force to said armature, said fluid pump further comprising:

an upper flow impedance member extending axially in said fluid passage which impedes circumferential flow of said fluid within said fluid passage, thereby generating a second pressure gradient circumferentially within said fluid passage which applies an upper lateral force to said armature;

wherein said lower flow impedance member is located within said fluid passage at a different circumferential location than said upper flow impedance member; and

wherein said lower flow impedance member extends axially within said fluid passage over a different axial range than said upper flow impedance member.

4. A fluid pump as in claim 3 wherein said lower flow impedance member extends axially within said fluid passage over a first axial range from a first lower flow impedance member end to a second lower flow impedance member end and said upper flow impedance member extends axially within said fluid passage over a second axial range from a first upper flow impedance member end to a second upper flow impedance member end such that said first axial range does not include said second axial range.

5. A fluid pump as in claim 3 wherein said lower lateral force and said upper later force act together to generate a moment couple on said armature.

6. A fluid pump as in claim 3 wherein said lower flow impedance member and said upper flow impedance member extend radially into said fluid passage from diametrically opposing locations of said stator.

7. A fluid pump as in claim 6 further comprising an axial flow separator located within said fluid passage which impedes axial flow of said fluid within said fluid passage, wherein said axial flow separator is located axially between said lower flow impedance member and said upper flow impedance member.

8. A fluid pump as in claim 7 wherein said axial flow separator is annular in shape and includes an axial flow separator flow aperture extending axially therethrough which provides fluid communication from said fluid passage to said outlet.

9. A fluid pump as in claim 8 wherein said axial flow separator flow aperture is not centered about said axis.

10. A fluid pump as in claim 3 further comprising an axial flow separator located within said fluid passage which impedes axial flow of said fluid within said fluid passage, wherein said axial flow separator is located axially between said lower flow impedance member and said upper flow impedance member.

11. A fluid pump as in claim 10 wherein said axial flow separator is annular in shape and includes an axial flow separator flow aperture extending axially therethrough which provides fluid communication from said fluid passage to said outlet.

12. A fluid pump as in claim 11 wherein said axial flow separator flow aperture is not centered about said axis.

13. A fluid pump as in claim 3 wherein said lower flow impedance member and said upper flow impedance member are fixed to said stator.

14. A fluid pump as in claim 3 wherein said lower flow impedance member is configured to apply said lower lateral force in a direction which is opposite in direction to a side load applied to said armature by said pumping arrangement.

15. A fluid pump as in claim 14 wherein said lower lateral force and said upper later force act together to generate a moment couple on said armature.