Rotor end ring with oil sleeve

Abstract

An electric motor includes: a housing; a stator having end turn windings; a rotatable central shaft; a rotor mounted on the central shaft; and a rotor end ring mounted on the central shaft adjacent to the rotor. The rotor end ring includes: an annular disc-shaped body having a circumferential outer diameter and a circumferential inner diameter and formed of a thermally conductive material; a recess formed in the front face of the body; an oil jacket formed in the back face of the body, the oil jacket including an annular channel having a circumferential outer wall and a circumferential inner wall; two inlets, each extending radially between the inner diameter of the body and the inner wall of the oil jacket; and a plurality of outlets, each including an arcuate slot, the plurality of outlets being equally spaced around the front face adjacent to the circumferential inner wall of the oil jacket.

Description

Technical Field

[0001] The present invention relates to an electric motor with a rotor end ring. Specifically, a rotor end ring of the present invention comprises an oil sleeve to improve the cooling characteristics of the rotor end ring. Background Art

[0002] Coolant is routed through the motor to provide cooling for the motor during operation. The current flowing within the motor generates heat, and if some of the heat is not removed, the motor can damage or fail. The coolant flowing through and through the rotor end ring absorbs the heat from the rotor end ring. Typically, the coolant passes through the rotor end ring and is pushed through the front face of the rotor end ring by centrifugal force. In current motors, the coolant is pushed outward toward the outer periphery of the rotor end ring without spreading out. This means that the coolant only flows through a localized area of ​​the front face of the rotor end ring.

[0003] Therefore, while current techniques achieve their intended purposes, a new and improved electric motor having a rotor end ring adapted to provide more efficient cooling of the rotor end ring is needed. Summary of the invention

[0004] According to several aspects of the present invention, a rotor end ring for an electric motor includes: an annular disc-shaped body having a circumferential outer diameter and a circumferential inner diameter; a recess formed in the front face of the body; an oil jacket formed in the back face of the body; at least one inlet adapted to allow coolant to enter the oil jacket; and a plurality of outlets adapted to allow coolant to flow from the oil jacket through the rotor end ring to the recess formed in the front face of the body.

[0005] According to another aspect, the oil jacket is an annular channel having a circumferential outer wall and a circumferential inner wall.

[0006] According to another aspect, the radius of the circumferential outer wall of the oil sleeve is at least about 5 mm smaller than the circumferential outer diameter of the body, and the radius of the circumferential inner wall of the oil sleeve is at least about 5 mm larger than the inner diameter of the body.

[0007] According to another aspect, the axial depth of the oil sleeve is approximately 0.1 times to 0.8 times the thickness of the rotor end ring.

[0008] According to another aspect, the axial depth of the oil sleeve is approximately 2 mm to 4 mm.

[0009] According to another aspect, at least one inlet extends radially between an inner diameter of the body and an inner wall of the oil jacket.

[0010] According to another aspect, the at least one inlet has an axial depth approximately equal to the axial depth of the oil jacket and a width of approximately 3 mm to 10 mm.

[0011] According to another aspect, the at least one inlet includes two inlets positioned approximately 180 degrees apart.

[0012] According to another aspect, the plurality of outlets are arcuate slots equally spaced in a circular pattern around the front face of the body.

[0013] According to another aspect, the plurality of outlets are located adjacent to a circumferential inner wall of the oil jacket.

[0014] According to another aspect, the radial width of the outlet is approximately 1 mm to 10 mm.

[0015] According to another aspect, the arc length of the outlet is equal to (360 degrees / N) x 0.95, where N is the number of outlets.

[0016] According to another aspect, the combined arc length of the plurality of outlets is less than or equal to approximately 342 degrees.

[0017] According to another aspect, the body is formed from a thermally conductive material.

[0018] According to several aspects of the present disclosure, a rotor end ring for an electric motor includes: an annular disc-shaped body having a circumferential outer diameter and a circumferential inner diameter and formed of a heat conductive material; a recess formed in the front face of the body; an oil jacket formed in the back face of the body, the oil jacket including an annular channel having a circumferential outer wall and a circumferential inner wall; two inlets positioned approximately 180 degrees apart, each extending radially between the inner diameter of the body and the inner wall of the oil jacket and adapted to allow coolant to enter the oil jacket; and a plurality of outlets, each including an arcuate slot, the outlets being equidistantly spaced in a circular pattern around the front face of the body adjacent to the circumferential inner wall of the oil jacket and adapted to allow coolant to flow from the oil jacket through the rotor end ring to the recess formed in the front face of the body.

[0019] According to another aspect, the radius of the circumferential outer wall of the oil sleeve is at least about 5 mm smaller than the circumferential outer diameter of the body, the radius of the circumferential inner wall of the oil sleeve is at least about 5 mm smaller than the inner diameter of the body, and the axial depth of the oil sleeve is approximately 0.1 times to 0.8 times the thickness of the rotor end ring.

[0020] According to another aspect, the axial depth of each inlet is approximately equal to the axial depth of the oil jacket and the width is approximately 3 mm to 10 mm, and the radial width of each outlet is approximately 1 mm to 10 mm and the arc length is equal to (360 degrees / N)×0.95, where N is the number of outlets.

[0021] According to several aspects of the present disclosure, an electric motor includes: a housing; a stator, which is fixedly mounted in the housing and has an end turn winding; a rotatable central shaft; a rotor, which is mounted on the central shaft for rotation in the stator, the stator, the central shaft and the rotor are all coaxially positioned in the housing; and a rotor end ring, which is mounted on the central shaft adjacent to the axial end of the rotor, the rotor end ring including: an annular disc-shaped body, which has a circumferential outer diameter and a circumferential inner diameter and is formed of a heat conductive material; a recess, which is formed in the front surface of the body an oil jacket formed in the back side of the body, the oil jacket comprising an annular channel having a circumferential outer wall and a circumferential inner wall; two inlets positioned approximately 180 degrees apart, each extending radially between the inner diameter of the body and the inner wall of the oil jacket and adapted to allow coolant to enter the oil jacket; and a plurality of outlets, each comprising an arcuate slot, the outlets being spaced equidistantly around the front side of the body in a circular pattern adjacent the circumferential inner wall of the oil jacket and adapted to allow coolant to flow from the oil jacket through the rotor end annulus to a recess formed in the front side of the body.

[0022] According to another aspect, the radius of the circumferential outer wall of the oil sleeve is at least about 5 mm smaller than the circumferential outer diameter of the body, the radius of the circumferential inner wall of the oil sleeve is at least about 5 mm smaller than the inner diameter of the body, and the axial depth of the oil sleeve is approximately 0.1 times to 0.8 times the thickness of the rotor end ring.

[0023] According to another aspect, the axial depth of each inlet is approximately equal to the axial depth of the oil jacket and the width is approximately 3 mm to 10 mm, and the radial width of each outlet is approximately 1 mm to 10 mm and the arc length is equal to (360 degrees / N)×0.95, where N is the number of outlets.

[0024] Further areas of applicability will become apparent from the description provided herein.It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

[0026] Figure 1 is a cross-sectional view of a motor having a rotor end ring according to an exemplary embodiment of the present invention;

[0027] Figure 2 is a perspective view of a rotor end ring according to an exemplary embodiment of the present invention;

[0028] Figure 3 yes Figure 1 An end view of a rotor end ring shown in ;

[0029] Figure 4 yes Figure 2 A schematic cross-sectional view of the rotor, rotor end rings and central shaft of the electric motor shown in ; and

[0030] Figure 5 is a schematic diagram of the rotor and rotor end ring, showing the coolant flow across the front face of the rotor end ring. DETAILED DESCRIPTION

[0031] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

[0032] Reference Figure 1 , an electric motor 10 according to an exemplary embodiment of the present invention includes a housing 12. A stator 14 is fixedly mounted in the housing 12. The stator 14 is generally cylindrical and includes end turn windings 16 on either axial end thereof. A rotatable central shaft 18 is supported by the housing 12 and extends longitudinally in the housing 12. A rotor 20 is mounted on the central shaft 18 for rotation in the stator 14. The stator 14, the central shaft 18, and the rotor 20 are all coaxially positioned in the housing 12. A rotor end ring 22 is mounted on the central shaft 18 adjacent to each axial end of the rotor 20. The central shaft 18, the rotor 20, and the rotor end ring 22 rotate integrally in the housing 12.

[0033] Heat is generated by the current flowing through the motor 10. A coolant is circulated through the motor 10 to remove the heat and prevent the motor 10 from overheating. The coolant is directed through a passage 26 formed in the center shaft 18, as indicated by arrows 28. At least one aperture 30 is formed in the center shaft 18 and allows the coolant to flow axially outward from the passage 26 to the rotor end ring 22.

[0034] Reference Figure 2 and Figure 3 , the rotor end ring 22 includes an annular disk-shaped body 32 having a circumferential outer diameter 34 and a circumferential inner diameter 36. The inner diameter 36 of the body 32 is adapted to engage the center shaft 18. The rotor end ring 22 may be attached to the center shaft 18 by any suitable means, such as, as a non-limiting example, an interference fit.

[0035] The rotor end ring 22 includes a recess 38 formed in a front face 40 of the body 32 and an oil jacket 42 formed in a rear face 44 of the body 32. At least one inlet 44 is in fluid communication with the at least one aperture 30 and is adapted to allow coolant to enter the oil jacket 42. A plurality of outlets 46 extend axially through the body 32 of the rotor end ring 22 and are adapted to allow coolant to flow from the oil jacket 42 through the rotor end ring 22 to the recess 38 formed in the front face 40 of the body 32.

[0036] Reference Figure 3 and Figure 4, the oil sleeve 42 is an annular channel having a circumferential outer wall 48 and a circumferential inner wall 50. In an exemplary embodiment, the radius 52 of the circumferential outer wall 48 of the oil sleeve 42 is at least about 5 mm smaller than the radius 53 of the circumferential outer diameter 34 of the body 32, and the radius 54 of the circumferential inner wall 50 of the oil sleeve 42 is at least about 5 mm smaller than the radius 55 of the inner diameter 36 of the body 32. The axial depth 56 of the oil sleeve 42 is about 0.2 times the axial thickness 58 of the rotor end ring 22 to 0.5 times the axial thickness 58 of the rotor end ring 22. In an exemplary embodiment, the axial thickness 58 of the rotor end ring 22 is about 6 mm, and the axial depth 56 of the oil sleeve 42 is about 2 mm to 4 mm.

[0037] At least one inlet 44 extends radially between the inner diameter 36 of the body 32 and the inner wall 50 of the oil jacket 42 and has an axial depth 60 approximately equal to the axial depth 56 of the oil jacket 42 and a width 62 of approximately 3 mm to 10 mm. As shown, in the exemplary embodiment, the rotor end ring 22 includes two inlets 44 radially spaced 180 degrees from each other.

[0038] Each of the plurality of outlets 46 is an arcuate slot. The plurality of outlets 46 are equally spaced around the front face 40 of the body 32 in a circular pattern. The outlets 46 are located near the circumferential inner wall 50 of the oil jacket 42. In an exemplary embodiment, the radial distance 64 between the outlet and the circumferential inner wall 50 of the oil jacket 42 is minimized and may be 0 mm. In an exemplary embodiment, the radial width 66 of the outlet 46 is approximately 1 mm to 10 mm, and the arc length 68 is approximately equal to (360 degrees / N)×0.95, where N is the number of outlets 46. As shown, in an exemplary embodiment, the rotor end ring 22 includes eight outlets 46, and the combined arc length 68 of the eight outlets 46 is less than or equal to approximately 342 degrees.

[0039] The rotor end ring 22 may be made of any thermally conductive material suitable for conducting heat from the electric motor 10 to the coolant. In an exemplary embodiment, the rotor end ring 22 is formed of aluminum.

[0040] In operation, the center shaft 18, the rotor 20, and the rotor end ring 22 all rotate integrally within the motor 10. When the coolant flows from the center shaft 18 into the oil jacket 46, the centrifugal force pushes the coolant radially outward, causing the coolant to collect radially outward from the outlet 46 into the oil jacket 42. Once a sufficient amount of coolant collects in the oil jacket 42, the coolant begins to flow axially through the outlet 46.

[0041] The location of the outlets 46 adjacent to the circumferential inner wall 50 of the oil jacket 42 allows the coolant to pool within the oil jacket 42, absorbing heat from the rotor end ring 22 and the rotor 20 itself. Because the coolant pools within the oil jacket 42, the coolant remains within the oil jacket 42 for a period of time, and heat is more efficiently absorbed by the coolant. In addition, the pooling of the coolant within the oil jacket 42 ensures that the coolant will flow out of all of the outlets 46 evenly. Rather than having the coolant flow immediately from the inlet 44 to the nearest outlet 46, the coolant must first fill the oil jacket 42 and be dispersed throughout the oil jacket 42. Once the coolant fills the oil jacket 42 to the point where the coolant will flow through the outlets 46, the coolant will flow evenly through all of the multiple outlets 46.

[0042] Reference Figure 5 Once the coolant flows axially through the outlet 46, the coolant is forced across the front face 40 of the rotor end ring 22 as indicated by arrows 70. The arcuate shape of the outlet 46 allows the coolant to be more evenly spread across the front face 40 of the rotor end ring 22, thereby providing better cooling for the rotor end ring 22.

[0043] Eventually, the coolant flows through the recess 38, flows radially outward toward the outer circumference 34 of the body 32, and flows radially outward onto the end turn windings 16 of the stator 14 to provide additional cooling for the end turn windings 16. Due to the rotation of the rotor end ring 22, the coolant is pushed by centrifugal force at a relatively high speed through the front face 40 of the rotor end ring 22 and provides cooling for the end turn windings 16.

[0044] The electric motor 10 and rotor end ring 22 of the present invention provide several advantages. These advantages include two-stage cooling of the electric motor 10. First, the coolant collects within the oil jacket 42 and absorbs heat from the rotor end ring 22 and the rotor 20 internally; second, the coolant flows outwardly through the outlet 46 and radially passes through the front face 40 of the rotor end ring 22 to provide additional cooling to the front face 40 of the rotor end ring 22. More efficient cooling of the rotor end ring 22 will reduce deformation of the rotor end ring 22 due to thermal expansion, and more uniform spreading of the coolant on the front face 40 of the rotor end ring 22 will allow for better spraying of the coolant onto the end turn windings 16 of the stator 14.

[0045] The description of the present disclosure is merely exemplary in nature, and changes that do not depart from the gist of the present disclosure are included within the scope of the present disclosure. These changes should not be regarded as departing from the spirit and scope of the present disclosure.

Claims

1. A rotor end ring for an electric motor, comprising: an annular disc-shaped body having a circumferential outer diameter and a circumferential inner diameter; a recess formed in the front surface of the body; an oil jacket formed in the back side of the main body; at least one inlet adapted to allow coolant to enter the oil jacket; as well as a plurality of outlets adapted to allow coolant to flow from the oil jacket through the rotor end annulus to a recess formed in the front face of the body, wherein the plurality of outlets comprises arcuate slots equally spaced in a circular pattern around the front face of the body, and wherein the plurality of outlets have a combined arc length less than or equal to 342 degrees. 2 . The rotor end ring according to claim 1 , wherein the oil sleeve is an annular channel having a circumferential outer wall and a circumferential inner wall.

3. The rotor end ring according to claim 2, wherein the radius of the circumferential outer wall of the oil sleeve is at least 5 mm smaller than the circumferential outer diameter of the main body, and the radius of the circumferential inner wall of the oil sleeve is at least 5 mm larger than the inner diameter of the main body. 4 . The rotor end ring according to claim 2 , wherein an axial depth of the oil sleeve is 0.2 times to 0.5 times the thickness of the rotor end ring.

5. The rotor end ring according to claim 2, wherein an axial depth of the oil sleeve is 2 mm to 4 mm.

6. The rotor end ring of claim 2, wherein the at least one inlet extends radially between an inner diameter of the body and an inner wall of the oil jacket.

7. The rotor end ring according to claim 6, wherein the at least one inlet has an axial depth equal to the axial depth of the oil jacket and a width of 3 mm to 10 mm.

8. The rotor end ring of claim 6, wherein the at least one inlet comprises two inlets positioned 180 degrees apart.

9. The rotor end ring of claim 2, wherein the plurality of outlets are located adjacent to a circumferential inner wall of the oil jacket.

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