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An electric machine having a stator, a rotor and a housing assembly with two end caps and inner and outer axially extending members. The outer housing member is disposed about the inner member. Ribs extend from one housing member and engage the other housing member in an interstitial space. The othe

An electric machine having a stator, a rotor and a housing assembly with two end caps and inner and outer axially extending members. The outer housing member is disposed about the inner member. Ribs extend from one housing member and engage the other housing member in an interstitial space. The other housing member may be a tubular sleeve. The ribs define axially extending fluid path segments within the interstitial space and the end caps close the opposite axial ends of the interstitial space and define an inlet and an outlet for a liquid coolant. The liquid coolant path may be serpentine. The housing member with ribs may include a sleeve portion with at least some ribs having a width greater than the radial thickness of the sleeve portion. Threaded fasteners can attach the end caps to the enlarged width ribs. The inner and outer housings are advantageously extrudable.

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1. An electric machine comprising: a stator operably coupled with a rotor wherein the stator includes a stator core and a plurality of windings and the rotor is rotatable about a rotational axis, the stator having a length extending the distance between distal limits of the windings at opposite axia

1. An electric machine comprising: a stator operably coupled with a rotor wherein the stator includes a stator core and a plurality of windings and the rotor is rotatable about a rotational axis, the stator having a length extending the distance between distal limits of the windings at opposite axial ends of the electric machine;a housing assembly including first and second end caps and inner and outer axially extending housing members wherein:the stator core is disposed within and thermally coupled with the inner axially extending housing member and the outer axially extending housing member is disposed about the inner axially extending housing member and defines an interstitial space radially therebetween;a plurality of ribs extends radially from one of the inner and outer housing members into the interstitial space, each of the ribs having a distal end which engages the opposite one of the inner and outer housing members, the opposite one of the inner and outer housing members being a tubular sleeve with a substantially smooth walled surface facing the interstitial space; the distal end of each of the plurality of ribs being engaged with the smooth walled surface; the plurality of ribs defining a plurality of axially extending fluid path segments within the interstitial space, the first and second end caps defining end turn passages through which fluid path segments are connected at opposite axial ends of the electric machine; andelectronic components located radially inward of the end turn passages;wherein the first and second end caps sealingly close the opposite axial ends of the interstitial space and the housing assembly defines an inlet and an outlet wherein a liquid coolant enters the inlet, flows along a fluid path including the plurality of axially extending fluid path segments and the end turn passages and is discharged through the outlet; andwherein the fluid path has a length extending the distance between two opposite axial limits of the fluid path end turn passages and the fluid path length is greater than the stator length, whereby liquid coolant flow along the fluid path helps to cool the electronic components. 2. The electric machine of claim 1 wherein the plurality of ribs extends radially outwardly from the inner housing member and the substantially smooth walled surface is a radially inward facing cylindrical surface. 3. The electric machine of claim 1 wherein the inner and outer housing members and first and second end caps define a serpentine path for the liquid coolant wherein the liquid coolant flows in opposite axial directions in circumferentially adjacent ones of the fluid path segments with the axial direction of the fluid flow being reversed between the adjacent segments at positions proximate the first and second end caps. 4. The electric machine of claim 3 wherein the inner and outer housing members have substantially the same axial length and wherein each of the plurality of ribs has an axial extent that is substantially equivalent to the axial length of the inner and outer housing members. 5. The electric machine of claim 4 wherein each of the first end and second end caps defines a plurality of fluid passageways communicating fluid between the adjacent segments. 6. The electric machine of claim 3 wherein the inner and outer housing members have substantially the same axial length and at least some of the plurality of ribs are shortened and have an axial extent that is less than the axial length of the inner and outer housing members, the shortened ribs defining a passageway which communicates fluid between the adjacent segments. 7. The electric machine of claim 6 wherein at least one of the first and second end caps defines a substantially planar surface engageable with the inner and outer housing members proximate the passageways defined by the shortened ribs. 8. The electric machine of claim 1 wherein the inner and outer housing members each have an axial length and define a cross section that is substantially uniform along the entire axial length of the respective housing member whereby the inner and outer housing members are each extrudable. 9. The electric machine of claim 8 wherein the opposite one of the inner and outer housing members is a substantially cylindrical sleeve. 10. The electric machine of claim 8 further comprising four sealing members wherein one of the sealing members is disposed at each axial end of each of the inner and outer housing members and each of the sealing members is sealingly engaged with and disposed between one of the first and second end caps and one of the inner and outer housing members. 11. The electric machine of claim 1 wherein the one of the inner and outer housing members having the plurality of ribs extending therefrom includes a tubular portion having a radial thickness and wherein at least some of the plurality of ribs define a circumferentially extending width greater than the radial thickness of the tubular portion. 12. The electric machine of claim 11 wherein the first and second end caps are secured with threaded fasteners extending into bores located in the ribs having circumferential widths greater than the radial thickness of the tubular portion. 13. The electric machine of claim 1 wherein the distance between a distal limit of the stator and an axial limit of the fluid path at one axial end of the electric machine, is greater than the distance between a distal limit of the stator and an axial limit of the fluid path at the opposite axial end of the electric machine. 14. An electric machine comprising: a stator operably coupled with a rotor wherein the stator includes a stator core and a plurality of windings and the rotor is rotatable about a rotational axis, the stator having a length extending the distance between distal limits of the windings at opposite axial ends of the electric machine;a housing assembly including first and second end caps and inner and outer axially extending housing members wherein: the stator core is disposed within and thermally coupled with the inner axially extending housing member and the outer axially extending housing member is disposed about the inner axially extending housing member and defines an interstitial space radially therebetween,a plurality of ribs extends radially from one of the inner and outer housing members into the interstitial space, each of the ribs having a distal end which engages the opposite one of the inner and outer housing members,the opposite one of the inner and outer housing members has a substantially smooth walled surface facing the interstitial space wherein the distal end of each of the plurality of ribs is engaged with the smooth walled surface,the plurality of ribs defines a plurality of axially extending fluid path segments within the interstitial space, the first and second end caps defining end turn passages through which fluid path segments are connected at opposite axial ends of the electric machine, andthe inner and outer housing members each define an axial length and a cross section that is substantially uniform along the entire axial length of the respective housing member whereby the inner and outer housing members are each extrudable;the one housing member including a tubular portion having a radial thickness wherein at least some of the plurality of ribs define a circumferentially extending width greater than the radial thickness of the tubular portion;a plurality of fasteners engaging the first and second end caps and extending into bores located in the ribs having circumferential widths greater than the radial thickness of the tubular portion to thereby secure the first and second end caps to the one housing member wherein the first and second end caps sealingly close the opposite axial ends of the interstitial space and define an inlet and an outlet wherein a liquid coolant enters the inlet, flows along a serpentine fluid path defined by the inner and outer housing members and the first and second end caps with the liquid coolant and is discharged through the outlet; andelectronic components located radially inward of the end turn passages;wherein the fluid path has a length extending the distance between two opposite axial limits of the fluid path end turn passages and the fluid path length is greater than the stator length, whereby liquid coolant flow along the fluid path helps to cool the electronic components. 15. The electric machine of claim 14 wherein the bores located in the ribs are threaded bores threadingly engaged with the plurality of fasteners. 16. The electric machine of claim 14 wherein the inner and outer housing members and first and second end caps define a serpentine path for the liquid coolant wherein the liquid coolant flows in opposite axial directions in circumferentially adjacent ones of the fluid path segments with the axial direction of the fluid flow being reversed between the adjacent segments at positions proximate the first and second end caps. 17. The electric machine of claim 16 wherein the inner and outer housing members have substantially the same axial length and wherein the plurality of ribs have an axial extent that is substantially equivalent to the axial length of the first and second housing members and wherein each of the first end and second end caps defines a plurality of fluid end turn passages communicating fluid between the adjacent fluid path segments. 18. The electric machine of claim 17 wherein the inner and outer housing members have substantially the same axial length and at least some of the plurality of ribs are shortened and have an axial extent that is less than the axial length of the inner and outer housing members, the shortened ribs defining end turn passages which communicate fluid between the adjacent segments and wherein at least one of the first and second end caps defines a substantially planar surface engageable with the inner and outer housing members proximate the end turn passages defined by the shortened ribs. 19. The electric machine of claim 14 wherein the rotor is mounted on a shaft and the rotor and shaft rotate together about the rotational axis; and the electric machine further comprises first and second bearing assemblies rotatably supporting the shaft on opposite axial ends of the rotor wherein the first bearing assembly is mounted on the first end cap and the second bearing assembly is mounted on the second end cap. 20. The electric machine of claim 14 wherein the plurality of ribs extends radially outwardly from the inner housing member and the outer housing member is a tubular cylindrical sleeve with substantially smooth walled radially inward facing and radially outward facing surfaces. 21. The electric machine of claim 14 further comprising four sealing members wherein one of the sealing members is disposed at each axial end of each of the first and second housing members and each of the sealing members is sealingly engaged with and disposed between one of the first and second end caps and one of the inner and outer housing members. 22. The electric machine of claim 14 wherein the distance between a distal limit of the stator and an axial limit of the fluid path at one axial end of the electric machine, is greater than the distance between a distal limit of the stator and an axial limit of the fluid path at the opposite axial end of the electric machine.