Abstract:
A system for cooling an electrical machine is disclosed. The electrical machine includes a stator including a plurality of coils, an exterior housing, and an end cap. During operation of the electrical machine, a fluid is sprayed from the end cap onto the plurality of coils to carry away heat generated by the electrical machine.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure relates to a system for cooling an electrical machine. More particularly, the present disclosure relates to an internal oil cooling system for an electrical machine. 
       BACKGROUND OF THE INVENTION 
       [0002]    Electrical machines, including motors and generators, generate heat during operation. To cool the electrical machine, air or liquid coolant may be directed through an exterior housing that surrounds the electrical machine, for example. During operation of the electrical machine, air or liquid coolant flows through the exterior housing, absorbing and carrying away heat from the electrical machine. As another example, the electrical machine may be submerged in a liquid coolant during operation. 
       SUMMARY 
       [0003]    The present disclosure provides an internal oil cooling system for an electrical machine. The electrical machine includes a stator including a plurality of coils, an exterior housing, and an end cap. During operation of the electrical machine, a fluid is sprayed from the end cap onto the plurality of coils to carry away heat generated by the electrical machine. 
         [0004]    According to an embodiment of the present disclosure, an electrical machine is provided including a stator, an exterior housing, and an end cap. The stator includes a plurality of coils, the stator defining an axial bore configured to receive a rotor. The exterior housing has a first axial end and a second axial end, the exterior housing defining an axial chamber configured to receive the stator. The end cap is configured to couple to at least one of the first and second axial ends of the exterior housing. The end cap includes a fluid inlet configured to receive a fluid and a plurality of fluid outlets, at least one of the plurality of fluid outlets configured to deliver the fluid from the fluid inlet to at least one of the plurality of coils. 
         [0005]    According to another embodiment of the present disclosure, an electrical machine is provided including a stator, an exterior housing, and an end cap. The stator includes a plurality of coils, the stator defining an axial bore configured to receive a rotor. The exterior housing has a first axial end and a second axial end, the exterior housing defining an axial chamber configured to receive the stator. The end cap is configured to couple to at least one of the first and second axial ends of the exterior housing. The electrical machine also includes a fluid inlet configured to receive a fluid and a plurality of fluid outlets defined by the end cap and configured to deliver the fluid from the fluid inlet to the plurality of coils. 
         [0006]    According to yet another embodiment of the present disclosure, a method is provided for cooling an electrical machine. The electrical machine includes a stator having a plurality of coils, an exterior housing that surrounds the stator and has a first axial end and a second axial end, and an end cap coupled to at least one of the first and second axial ends of the exterior housing. The method includes the steps of delivering a liquid coolant to the end cap of the electrical machine and spraying the liquid coolant from the end cap onto the plurality of coils of the stator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the disclosure itself will be better understood by reference to the following description taken in conjunction with the accompanying drawings, wherein: 
           [0008]      FIG. 1  is a top plan view of an exemplary electrical machine of the present disclosure including an exterior housing and a stator; 
           [0009]      FIG. 1A  is a cross-sectional view of the electrical machine of  FIG. 1 , taken along line A-A of  FIG. 1 ; 
           [0010]      FIG. 2  is a top plan view of the electrical machine of  FIG. 1 , further including end caps coupled to the exterior housing; 
           [0011]      FIG. 2A  is a cross-sectional view of the electrical machine of  FIG. 2 , taken along line A-A of  FIG. 2 ; 
           [0012]      FIG. 2B  is a cross-sectional view of the electrical machine of  FIG. 2 , taken along line B-B of  FIG. 2 ; 
           [0013]      FIG. 2C  is a detailed view of a portion of the electrical machine of  FIG. 2A ; 
           [0014]      FIG. 2D  is a detailed view of a portion of the electrical machine of  FIG. 2B ; 
           [0015]      FIG. 3  is a top plan view of one of the end caps of  FIG. 2 ; 
           [0016]      FIG. 3A  is a cross-sectional view of the end cap of  FIG. 3 , taken along line A-A of  FIG. 3 ; 
           [0017]      FIG. 3B  is a cross-sectional view of the end cap of  FIG. 3 , taken along line B-B of  FIG. 3 ; 
           [0018]      FIG. 4  is a top plan view of another exemplary electrical machine of the present disclosure including an exterior housing and a stator; 
           [0019]      FIG. 4A  is a cross-sectional view of the electrical machine of  FIG. 4 , taken along line A-A of  FIG. 4 ; 
           [0020]      FIG. 5  is a cross-sectional view of the electrical machine of  FIG. 4 , further including a first and second end caps coupled to the exterior housing; 
           [0021]      FIG. 5A  is a cross-sectional view of the electrical machine of  FIG. 5 , taken along line A-A of  FIG. 5 ; 
           [0022]      FIG. 5B  is a cross-sectional view of the electrical machine of  FIG. 5 , taken along line B-B of  FIG. 5 ; 
           [0023]      FIG. 6  is a top plan view of the first end cap of  FIG. 5A ; 
           [0024]      FIG. 6A  is a cross-sectional view of the first end cap of  FIG. 6 , taken along line A-A of  FIG. 6 ; 
           [0025]      FIG. 6B  is a cross-sectional view of the first end cap of  FIG. 6 , taken along line B-B of  FIG. 6 ; 
           [0026]      FIG. 7  is a top plan view of the second end cap of  FIG. 5A ; 
           [0027]      FIG. 7A  is a cross-sectional view of the second end cap of  FIG. 7 , taken along line A-A of  FIG. 7 ; 
           [0028]      FIG. 7B  is a cross-sectional view of the second end cap of  FIG. 7 , taken along line B-B of  FIG. 7 ; 
           [0029]      FIG. 8  is a schematic representation of an exemplary method for cooling the electrical machine of  FIGS. 1-3 ; and 
           [0030]      FIG. 9  is a schematic representation of an exemplary method for cooling the electrical machine of  FIGS. 4-7 . 
       
    
    
       [0031]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the disclosure and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION 
       [0032]      FIGS. 1-2  illustrate an exemplary electrical machine in the form of motor  10 . Although the electrical machine is illustrated and described herein as motor  10 , machines of the present disclosure may also include generators, for example. Motor  10  includes stator  12 . Stator  12  is substantially cylindrical and defines axial bore  14  configured to receive a rotor (not shown). In operation, power is supplied to motor  10  to rotate the rotor relative to the surrounding stator  12 . 
         [0033]    Stator  12  includes outer periphery  16  and inner periphery  18 . Inner periphery  18  of stator  12  surrounds axial bore  14  and also includes a plurality of radially-spaced winding teeth  20 . Wires, such as insulated copper wires, wrap repeatedly around each winding tooth  20  of stator  12  to form coils  24 . End turns  26  of coils  24  are formed as the wires reverse direction at both axial ends  28  of stator  12  to wrap the wires repeatedly around each winding tooth  20 . 
         [0034]    Referring to  FIGS. 1 and 1A , motor  10  also includes exterior housing  30 . Exterior housing  30  is substantially cylindrical and includes inner wall  32  that defines axial bore  34 . Exterior housing  30  also includes axial ends  36 . Exterior housing  30  may be constructed of a steel tube, for example. To assemble motor  10 , exterior housing  30  may be prepared to receive stator  12 . More particularly, exterior housing  30  may be cut to length to receive stator  12  between axial ends  36  of exterior housing  30 , and inner wall  32  of exterior housing  30  may be sized and shaped to receive stator  12  in axial bore  34  of exterior housing  30 . For example, as shown in  FIGS. 1 and 1A , inner wall  32  of exterior housing  30  may be sized and shaped to contact and frictionally engage outer periphery  16  of stator  12 . As discussed in more detail below, inner wall  32  of exterior housing  30  may include chamfer  38  at both axial ends  36 . Also, both axial ends  36  of exterior housing  30  may include attachment apertures  40  formed by tapping or drilling holes axially into axial ends  36  of exterior housing  30 , for example. 
         [0035]    Exterior housing  30  of motor  10  also includes at least one drain port  42  that extends radially through exterior housing  30 . As shown in  FIG. 1A , motor  10  includes two drain ports  42 . Drain ports  42  may be formed by tapping or drilling holes radially into exterior housing  30 , for example. According to an exemplary embodiment of the present disclosure, each drain port  42  is located near axial end  36  of exterior housing  30  to be positioned axially beyond the corresponding axial end  28  of stator  12 . Each drain port  42  may be configured to receive hydraulic fitting  44  for draining fluid from motor  10 . It is within the scope of the present disclosure that inner wall  32  of exterior housing  30  may be tapered to direct fluid toward drain port  42 . 
         [0036]    Referring to  FIGS. 2-2D , motor  10  further includes at least one substantially circular end plate or cap  50 . Each end cap  50  may be constructed of steel or cast iron, for example. In the illustrated embodiment, motor  10  includes two substantially identical end caps  50 , each end cap  50  coupled to a corresponding axial end  36  of exterior housing  30 . Each end cap  50  may include a first, cap portion  50   a  that rests against axial end  36  of exterior housing  30  and a second, cylindrical portion  50   b  that extends within axial bore  34  of exterior housing  30 . To secure end caps  50  to exterior housing  30 , cap portion  50   a  of each end cap  50  may include attachment apertures  52  that align with attachment apertures  40  in exterior housing  30  for receiving a suitable fastener (not shown), such as a screw or a bolt. Seal  54 , such as an elastomeric O-ring, may be positioned between exterior housing  30  and each end cap  50  to seal the components. According to an exemplary embodiment of the present disclosure, seal  54  may be retained between cylindrical portion  50   b  of each end cap  50  and chamfer  38  in inner wall  32  of exterior housing  30 . 
         [0037]    With end cap  50  secured to exterior housing  30 , motor  10  includes an internal, annular channel  56  that extends substantially about the circumference of motor  10 . In the illustrated embodiment of  FIGS. 2C and 2D , cylindrical portion  50   b  of end cap  50  includes circumferential notch  57  that cooperates with inner wall  32  of exterior housing  30  to define annular channel  56 . It is also within the scope of the present disclosure that stator  12  may cooperate with end cap  50  and exterior housing  30  to define annular channel  56 . Forming part of annular channel  56  with end cap  50  and the rest of annular channel  56  with exterior housing  30  and/or stator  12 , rather than forming annular channel  56  entirely within end cap  50 , simplifies the construction of end cap  50 . For example, in the illustrated embodiment of  FIGS. 2C and 2D , end cap  50  may be constructed to include circumferential notch  57  rather than a hollow chamber that extends entirely within end cap  50 . 
         [0038]    As shown in  FIG. 2 , each end cap  50  may include central bore  58 . When motor  10  is fully assembled, a bearing or shaft of the rotor (not shown) may extend through central bore  58  of each end cap  50 . End cap  50  may support the rotor shaft in central bore  58  during operation of motor  10 . 
         [0039]    To secure motor  10  to another mechanical device, such as the mechanical device powered by motor  10 , each end cap  50  may also include mounting apertures  59 . Like attachment apertures  52  of end cap  50 , mounting apertures  59  of end cap  50  may be configured to receive a fastener (not shown), such as a screw or a bolt. In this embodiment, end caps  50  may serve as mounting brackets for mounting motor  10  to another mechanical device. 
         [0040]    An exemplary end cap  50  is shown in more detail in  FIGS. 3 ,  3 A, and  3 B. End cap  50  of motor  10  includes at least one entry port  60  that extends radially into end cap  50 . Entry port  60  may be formed by tapping or drilling holes radially into cap portion  50   a  of end cap  50 , for example. Entry port  60  of end cap  50  may be configured to receive hydraulic fitting  62  for injecting fluid into motor  10 . 
         [0041]    As shown in  FIG. 3A , end cap  50  includes entry channel  64  that extends between entry port  60  of end cap  50  and annular channel  56  of motor  10  which is partially defined by notch  57  of end cap  50 . Entry channel  64  may be formed by tapping or drilling holes axially into end cap  50 , and in particular, into cap portion  50   a  of end cap  50 . In operation, fluid injected into entry port  60  may be directed into annular channel  56  of motor  10  via entry channel  64 . 
         [0042]    As shown in  FIG. 3B , end cap  50  also includes a plurality of discharge channels  66 . Discharge channels  66  extend from annular channel  56  of motor  10  which is partially defined by notch  57  of end cap  50 . Discharge channels  66  may be formed by tapping or drilling holes into end cap  50 , and in particular, into cylindrical portion  50   b  of end cap  50 . In operation, fluid injected into entry port  60  may be directed into annular channel  56  of motor  10  via entry channel  64 , and fluid in annular channel  56  of motor  10  may be directed toward coils  24  of stator  12  via discharge channels  66 . According to an exemplary embodiment of the present disclosure, discharge channels  66  are spaced radially about end cap  50 . Each discharge channel  66  may align with a corresponding end turn  26  of coils  24  to direct fluid onto that end turn  26 . As shown by comparing  FIGS. 3A and 3B , discharge channels  66  may be aligned substantially parallel to entry channel  64 . However, it is also within the scope of the present disclosure that discharge channels  66  may extend radially inward from annular channel  56  toward coils  24  of stator  12  ( FIGS. 2A and 2B ). For example, discharge channels  66  may extend at an angle through cylindrical portion  50   b  of end cap  50 . 
         [0043]    Referring again to  FIG. 3A , end cap  50  may also include a bearing channel  68  that extends between entry port  60  and central bore  58  of end cap  50 . Bearing channel  68  may be formed by tapping or drilling holes radially inwardly into end cap  50 . In operation, fluid injected into entry port  60  may be directed either toward central bore  58  via bearing channel  68  or into annular channel  56  of motor  10  via entry channel  64 . 
         [0044]    Referring back to  FIGS. 2C and 2D , during operation of motor  10 , a liquid coolant, such as oil, is delivered to motor  10  for cooling. As shown in  FIG. 2C , the oil may be directed through an external hydraulic hose or tube (not shown), for example, and into entry port  60  of one or both end caps  50 . If end cap  50  includes bearing channel  68 , some of the oil that enters entry port  60  may flow toward central bore  58  ( FIG. 2A ) of end cap  50  via bearing channel  68  to lubricate the rotor shaft (not shown). The rest of the oil that enters entry port  60  flows into annular channel  56  of motor  10  via entry channel  64 , such that the oil substantially surrounds stator  12 . Next, as shown in  FIG. 2D , the oil sprays onto coils  24  of stator  12  from annular channel  56  via discharge channels  66  that are spaced radially about stator  12 . For example, the oil may spray onto end turns  26  of coils  24  via discharge channels  66 . Upon contacting coils  24 , the oil absorbs and carries away heat from coils  24 . As a result, the cooled coils  24  draw heat away from the center of motor  10  toward end caps  50 . As shown in  FIG. 2A , the heated oil then exits motor  10  through drain ports  42  of exterior housing  30 . It is also within the scope of the present disclosure that the heated oil may exit from end caps  50  of motor  10  rather than from exterior housing  30  of motor  10 . Drain ports  42  may be positioned along the bottom of motor  10  such that the heated oil exits motor  10  under the force of gravity. The oil may be directed from drain ports  42  through external hydraulic hoses or tubes (not shown), for example. The oil that exits motor  10  may be cooled and recycled through motor  10  for further cooling. 
         [0045]    The above-described cooling method is also illustrated schematically in  FIG. 8 . First, the oil is directed through entry port  60  of one or both end caps  50 . Next, the oil either flows through bearing channel  68  toward central bore  58  of each end cap  50  to lubricate rotor shaft  80 , or the oil flows through entry channel  64  into annular channel  56  of motor  10 . Then, from annular channel  56 , the oil flows through discharge channels  66  and onto end turns  26  of coils  24  of stator  12 . After contacting and cooling coils  24  of stator  12 , the heated oil exits motor  10  through drain port  42  of exterior housing  30 . 
         [0046]    The present disclosure may eliminate the need for an external cooling jacket, which may increase the size and weight of motor  10 . Also, rather than submerging motor  10  in oil, the present disclosure provides for a continuous flow of oil into and out of motor  10 , which may reduce resistance on motor  10  and improve the efficiency of motor  10 . 
         [0047]      FIGS. 4-5  provide another exemplary electrical machine in the form of motor  10 ′. Except as described below, motor  10 ′ includes many elements that are identical or substantially identical to those of motor  10 , and the same reference numerals followed by a prime symbol are used to designate identical or substantially identical elements therebetween. 
         [0048]    As shown in  FIGS. 4 and 4A , motor  10 ′ includes stator  12 ′ and exterior housing  30 ′. Outer periphery  16 ′ of stator  12 ′ includes radially spaced notches  70 ′ that cooperate with inner wall  32 ′ of exterior housing  30 ′ to define axial ducts  72 ′. 
         [0049]    Referring next to  FIGS. 5 ,  5 A, and  5 B, motor  10  further includes first end cap  50 ′ and second end cap  50 ″. In the illustrated embodiment, first end cap  50 ′ and second end cap  50 ″ are coupled to opposite axial ends  36 ′ of exterior housing  30 ′. With first and second end caps  50 ′,  50 ″, secured to exterior housing  30 ′, motor  10  includes a first annular channel  56 ′ and a second annular channel  56 ″. In the illustrated embodiment of  FIGS. 5A and 5B , cylindrical portion  50   b ′ of first end cap  50 ′ cooperates with inner wall  32 ′ of exterior housing  30 ′ and stator  12 ′ to define first annular channel  56 ′, and at the opposing axial end  36 ′ of motor  10 ′, cylindrical portion  50   b ″ of second end cap  50 ″ cooperates with inner wall  32 ′ of exterior housing  30 ′ and stator  12 ′ to define second annular channel  56 ″. As discussed below, first and second annular channels  56 ′,  56 ″, of first and second end caps  50 ′,  50 ″, cooperate with axial ducts  72 ′ of stator  12 ′. 
         [0050]    An exemplary first, or non-drive, end cap  50 ′ is shown in more detail in  FIGS. 6 ,  6 A, and  6 B. First end cap  50 ′ includes entry port  60 ′ and drain port  42 ′. As shown in  FIG. 6A , cylindrical portion  50   b ′ of first end cap  50 ′ is tapered to direct fluid toward drain port  42 ′. As shown in  FIG. 6B , first end cap  50 ′ also includes entry channel  64 ′ that extends between entry port  60 ′ and first annular channel  56 ′ and a plurality of discharge channels  66 ′ that extend radially inward from first annular channel  56 ′ toward stator  12 ′ ( FIG. 5B ). First end cap  50 ′ further includes bearing channel  68 ′ that extends between entry port  60 ′ and central bore  58 ′ of first end cap  50 ′, as shown in  FIG. 6A . 
         [0051]    An exemplary second, or drive, end cap  50 ″ is shown in more detail in  FIGS. 7 ,  7 A, and  7 B. Second end cap  50 ″ includes drain port  42 ″. As shown in  FIG. 7A , cylindrical portion  50   b ″ of second end cap  50 ″ is tapered to direct fluid toward drain port  42 ″. As shown in  FIG. 7B , second end cap  50 ″ also includes a plurality of discharge channels  66 ″ that extend radially inward from second annular channel  56 ″ toward stator  12 ′ ( FIG. 5B ). Second end cap  50 ″ further includes bearing channel  68 ″ that extends between second annular channel  56 ″ and central bore  58 ″ of second end cap  50 ″, as shown in  FIG. 7A . 
         [0052]    Referring back to  FIGS. 5 ,  5 A, and  5 B, during operation of motor  10 ′, a liquid coolant, such as oil, is delivered to motor  10 ′ for cooling. As shown in  FIG. 5A , the oil may be directed through an external hydraulic hose or tube (not shown), for example, and into entry port  60 ′ of first end cap  50 ′. If first end cap  50 ′ includes bearing channel  68 ′, some of the oil that enters entry port  60 ′ may flow toward central bore  58 ′ of first end cap  50 ′ via bearing channel  68 ′ to lubricate the rotor shaft (not shown). The rest of the oil that enters entry port  60 ′ flows into first annular channel  56 ′ of motor  10 ′ via entry channel  64 ′, such that the oil substantially surrounds stator  12 ′. From first annular channel  56 ′, the oil either sprays onto end turns  26 ′ of coils  24 ′ of stator  12 ′ via discharge channels  66 ′ of first end cap  50 ′, as shown in  FIG. 5B , or the oil flows axially down the outer periphery  16 ′ of stator  12 ′ via axial ducts  72 ′, as shown in  FIG. 5A . In this embodiment, the oil cools coils  24 ′ of stator  12 ′, as well as stator  12 ′ itself. After flowing through axial ducts  72 ′, the oil enters second annular channel  56 ″, such that the oil substantially surrounds stator  12 ′. From second annular channel  56 ″, the oil either sprays onto end turns  26 ′ of coils  24 ′ of stator  12 ′ via discharge channels  66 ″ of second end cap  50 ″, as shown in  FIG. 5B , or the oil flows toward central bore  58 ″ of second end cap  50 ″ via bearing channel  68 ″ to lubricate the rotor shaft (not shown), as shown in  FIG. 5A . After contacting coils  24 ′ of stator  12 ′, the heated oil may exit motor  10 ′ from either drain port  42 ′ of first end cap  50 ′ or drain port  42 ″ of second end cap  50 ″. The oil that exits motor  10 ′ may be cooled and recycled through motor  10 ′ for additional cooling. 
         [0053]    As mentioned above, axial ducts  72 ′ may be provided in communication with first and second annular channels  56 ′,  56 ″, to cool outer periphery  16 ′ of stator  12 ′ in addition to coils  24 ′ of stator  12 ′. This embodiment may enhance the cooling of motor  10 ′, especially a long motor  10 ′. 
         [0054]    The above-described cooling method is also illustrated schematically in  FIG. 9 . First, the oil is directed through entry port  60 ′ of first end cap  50 ′. Next, the oil either flows through bearing channel  68 ′ toward central bore  58 ′ of first end cap  50 ′ to lubricate rotor shaft  80 ′, or the oil flows through entry channel  64 ′ into first annular channel  56 ′ of motor  10 ′. From first annular channel  56 ′, the oil either flows through discharge channels  66 ′, onto end turns  26 ′ of coils  24 ′ of stator  12 ′, and out through drain port  42 ′ of first end cap  50 ′, or the oil flows through axial ducts  72 ′ to second annular channel  56 ″. From second annular channel  56 ″, the oil either flows through discharge channels  66 ″, onto end turns  26 ′ of coils  24 ′ of stator  12 ′, and out through drain port  42 ″ of second end cap  50 ″, or the oil flows through bearing channel  68 ″ of second end cap  50 ″ toward central bore  58 ″ of second end cap  50 ″ to lubricate rotor shaft  80 ′. 
         [0055]    While this invention has been described as having preferred designs, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.