Patent Publication Number: US-2022239170-A1

Title: Integrated stator cooling jacket system

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a Continuation-in-Part of U.S. Non-Provisional application Ser. No. 16/739,264 filed Jan. 10, 2020, which claims the benefit of an earlier filing date from U.S. Provisional Application Ser. No. 62/793,215 filed Jan. 16, 2019, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Exemplary embodiments pertain to the art of electric motors and, more particularly, to an electric motor having an integrated stator cooling system. 
     During operation, electric motors produce heat. Often times, rotating components of an electric motor may support a fan member that directs a flow of air through internal motor components. The flow of air may help with smaller systems, such as alternators, and systems that are installed in in open areas, such as generators. The flow of air is not always sufficient in high output systems, particularly those installed in closed areas, such as motor vehicle engine compartments. 
     Electric motors that are employed as prime movers in a motor vehicle typically include a liquid coolant system. The electric motor includes a stator formed from a plurality of stator laminations and a rotor. The liquid cooling system may include an inlet that receives coolant and an outlet that guides coolant to a heat exchange system. The coolant may flow in a jacket arranged radially outwardly of a stator of the electric motor. Specifically, the coolant may flow through small openings in the housing down onto end turns of a stator winding. The coolant runs over the end turns and passes to the outlet. Transferring heat from the end turns to the coolant reduces a portion of an overall heat signature of the electric motor. However, the end turns have a relatively small surface area relative to an overall size of the stator thereby limiting cooling efficiency. 
     Other systems rely on direct contact between an outer surface of the stator and an inner surface of a motor housing. In some cases, a cooling jacket may be defined at the inner surface of the housing. Heat may flow from the stator, through the housing, into the coolant passing through the cooling jacket. Indirect contact between a coolant and a surface to be cooled limits heat transfer capacity. In other systems, the heat may pass from an outer surface of the stator into coolant flowing through the housing. The outer surface of the stator possess a relatively small surface area when considered in relation to an overall area of the stator laminations. Accordingly, the industry would be receptive to electric motor cooling systems that remove heat from a larger surface area of the stator directly into a coolant to increase cooing efficacy. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Disclosed is an electric machine including a housing having an outer surface, an inner surface, a coolant inlet, and a coolant outlet, and a stator mounted in the housing. The stator includes a stator core formed from a plurality of stator laminations arranged in a first lamination group and a second lamination group that is circumferentially off-set from the first lamination group. The first lamination group and the second lamination group form a coolant flow path that extends circumferentially about and axially across the stator. Each of the plurality of stator laminations of the first lamination group and the second lamination group include a body having an inner surface section and an outer surface section, the inner surface section including a plurality of stator teeth and a plurality of cooling channels defining members integrally formed with and extending radially outwardly from the outer surface section. The plurality of cooling channel defining members create a coolant flow path that extends circumferentially in a first plurality of channels and axially in a second plurality of channels across the stator. 
     Also disclosed is a stator including a stator core formed from a plurality of laminations arranged in a first lamination group and a second lamination group that is circumferentially off-set from the first lamination group. The first lamination group and the second lamination group form a coolant flow path that extends circumferentially about and axially across the stator. Each of the plurality of laminations of the first lamination group and the second lamination group include a body having an inner surface section and an outer surface section. The inner surface section includes a plurality of stator teeth. A plurality of cooling channels defining members is integrally formed with and extend radially outwardly from the outer surface section. The plurality of cooling channel defining members create a coolant flow path that extends circumferentially in a first plurality of channels and axially in a second plurality of channels across the stator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts an electric motor including a stator formed from a plurality of stator laminations, in accordance with an aspect of an exemplary embodiment; 
         FIG. 2  depicts a stator lamination of the stator of  FIG. 1 ; 
         FIG. 3  depicts stator laminations arranged in a first lamination group radially off-set from stator laminations of a second lamination group, in accordance with an aspect of an exemplary embodiment; 
         FIG. 4  depicts a coolant flow path formed from a plurality of the stator lamination groups defining the stator of  FIG. 1 ; 
         FIG. 5  depicts a partially disassembly view of the stator of  FIG. 1  illustrating first and second end rings that are mounted to the stator laminations, in accordance with a non-limiting example; 
         FIG. 6  depicts the first and second end rings mounted to the stator laminations, in accordance with a non-limiting example; 
         FIG. 7  is a plan view of an inner surface of the second end ring depicting coolant spray notches that guide coolant onto stator end turns, in accordance with a non-limiting example; 
         FIG. 8  is a partial cross-sectional view of the stator core depicting coolant flow passing from a coolant spray notch onto a stator end turn, in accordance with a non-limiting example; and 
         FIG. 9  is a cross-sectional view of the electric motor of  FIG. 1  in accordance with a non-limiting example. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     With initial reference to  FIG. 1 , an electric motor in accordance with a non-limiting example, is indicated generally at  10 . Electric motor  10  includes a housing  14  having an outer surface  16  and an inner surface  18 . Housing  14  also includes a coolant inlet  22  and a coolant outlet  24 . The particular location and orientation of coolant inlet  22  and coolant outlet  24  may vary. Electric motor  10  includes a stator  26  arranged in housing  14 . Stator  26  includes a stator core  28  having a first axial end  29  and a second axial end  30  that is opposite first axial end  29 . Stator core  28  is coupled to inner surface  18  of housing  14 . Stator  26  includes a first end turn  32  and a second end turn  34 . In a non-limiting example, coolant inlet  22  and coolant outlet  25  are radially aligned and arranged axially inwardly of each axial end  29 ,  30  of stator  26 . 
     In accordance with a non-limiting example, stator  26  is formed from a plurality of stator laminations  37  having an outer diameter  38  as will be detailed more fully herein. Stator laminations  37  are arranged in a plurality of lamination groups including a first lamination group  39  and a second lamination group  41 . The number of lamination groups may vary. Second lamination group is circumferentially off-set relative to first lamination group  39 . In an embodiment, second lamination group  41  may be circumferentially off-set from first lamination group  39  by about 30°. 
     In a non-limiting example, first lamination group  39  is formed from a first plurality of laminations  42  spaced one, from another by a corresponding one of a first plurality of channels  44 . Similarly, second lamination group  41  is formed from a plurality of laminations such as shown at  46  spaced one from another by a corresponding one of a second plurality of channels  48 . First and second pluralities of channels  44  and  48  form part of a coolant flow path (not separately labeled) that extends circumferentially about plurality of laminations  37 . 
     In a non-limiting example plurality of laminations  37  is formed by stacking and interleaving the first plurality of laminations  42  of first lamination group  39  with corresponding ones of the second plurality of laminations  46  forming second lamination group  41 . In a non-limiting example, each of the second plurality of laminations  46  is circumferentially offset from corresponding ones of the first plurality of laminations  42  forming first lamination group  39 . The circumferential offset creates the first and second pluralities of channels  44  and  48 . Each of the first plurality of channels  44  is axially and circumferentially offset relative to corresponding ones of each of the second plurality of channels  48 . In a non-limiting example, inner surface  18  of housing  14  defines an outer boundary of the first and second pluralities of channels  46  and  48  and thus forms a surface of the coolant flow path  50 . Reference will now follow to  FIG. 2  in describing one of the first plurality of stator lamination  42  that may form part of first lamination group  39 . Stator lamination  42  includes a body  54  having an inner surface section  56  and an outer surface section  58 . Inner surface section  56  supports a plurality of radially inwardly projecting stator teeth  60 . In accordance with an exemplary embodiment, outer surface section  58  supports a plurality of cooling channel defining members, one of which is indicated at  64 . At this point, it should be understood that each of the second plurality of laminations  46  includes a second plurality of cooling channel defining members such as shown at  66  in  FIG. 3 . Further, it should be understood that the first plurality of laminations  42  and the second plurality of laminations  46  may be similarly formed. 
     In an embodiment, each cooling channel defming member  64  is radially off-set from an adjacent cooling channel defining member  64  by about 30°. It should be understood that the number of cooling channel defining members  64  may vary as may the off-set between adjacent cooling channel defining members  64 . Further, the offset may be different from or may be substantially the same as the off-set between adjacent lamination groups. 
     In accordance with an exemplary embodiment, each cooling channel defining member  64  includes a first circumferentially extending portion  68  and a second circumferentially extending portion  70 . First circumferentially extending portion  68  is spaced from second circumferentially extending portion  70  by a gap  71 . First circumferentially extending portion  68  is also spaced from outer surface section  58  to establish a first cooling channel portion  72  and second circumferentially extending portion  70  is spaced from outer surface section  58  to establish a second cooling channel portion  73 . 
     Each of the first plurality of stator lamination  42  includes an opening  83  formed in each of the plurality of cooling channel defining members  64  and a partial opening  85  formed in third cooling channel portion  80 . First and second lamination group  39  and  41  may be offset relative to one another and joined as shown in  FIG. 3 . In an embodiment, each circumferentially extending portion  68 ,  70  may include a recess or notch (not separately labeled) on an outer surface portion (also not separately labeled). The recess forms a bonding element receiving zone that may aid in joining stator  26  to inner surface  18  of housing  14 . At this point, it should be understood that each of the second plurality of stator laminations  46  are similarly formed. 
     In an embodiment, a number of the first plurality of stator laminations  42 , for example six (6) stator laminations, may be joined to form first lamination group  39 . Similarly, a number of the second plurality of stator laminations  46 , for example six (6) stator laminations, may be joined to form second lamination group  41  that is circumferentially offset relative to and combined with first lamination group  39 . That is, each lamination  42  may be interleaved with each lamination  46  when lamination groups  39  and  41  are formed. Additional lamination groups may be formed and joined together, each offset relative to another to form stator  26  such as shown in  FIG. 4 . At this point, it should be understood that the number of laminations in a lamination group may vary. Further, while channels  44  and  48  are shown as having a thickness of a single lamination, the thickness of each channels  44  and  48  may vary by adjusting how many laminations are combined prior to being interleaved. 
     In a non-limiting example, when first lamination group  39  and second lamination group  41  are combined, a split coolant path is formed as shown in  FIG. 4 . That is, coolant, such as oil, entering coolant inlet  22  ( FIG. 1 ) passes into channels  44  and  48  and flows circumferentially about stator core  30 . The coolant passes axially through coolant passages defined by first and second cooling channel portions  72  and  73 , passes through first plurality and second plurality of channels  44  and  48  and enters into coolant outlet  24 . Dividing coolant flow into channels  44  and  48  via first and second cooling channel portions  72  and  73  reduces a pressure drop of the coolant and thus enhances stator cooling efficiency. 
     In a non-limiting example, a portion of the coolant entering coolant inlet  22  flows counter-clockwise through channels  44  until reaching cooling channel portion  72 . The coolant flows into cooling channel portion  72  in both axial directions. A portion of the coolant may pass from cooling channel portion  72  and flow counter-clockwise into channels  48 . A second portion of the coolant flow may pass axially out the channel  72  and onto stator end turns  32  and/or  34 . Additional coolant may pass into channels  48  and then into cooling channel portion  73 . The second portion of the coolant may flow through cooling channel portion  73  in channel  73  in both axial directions. A third portion of the coolant may flow into an adjacent one of channels  44  and or may flow axially outwardly onto stator end turn  32  and/or  34 . The pattern repeats itself counter-clockwise until all the coolant is expelled axially from cooling channel portions  72  and  73 . 
     In a non-limiting example shown in  FIG. 5 , a first end ring  87  and a second end ring  88  may be installed on opposing sides of stator core  30 . First and second end rings  87  and  88  may be connected through a plurality of mechanical fasteners, one of which is indicated at  91  that extend through corresponding ones of openings  83  and partial openings  85  in first and second groups of laminations  39  and  41  as shown in  FIG. 6 . As will be detailed herein, end rings  87  and  88  cooperate with the coolant passages defined by first and second cooling channel portions  72  and  73  to deliver coolant to first and second end turns  32  and  34  of stator  26   
     In a non-limiting example shown in  FIG. 7 , end ring  88  includes a plurality of openings, one of which is shown at  100  that are receptive of corresponding ones of the plurality of mechanical fasteners  95 . End ring  88  includes an inner surface  110  that abuts one of the plurality of laminations  37 . In a non-limiting example, inner surface  110  includes a plurality of locator elements  118  that orient end ring  88  to stator core  30 . That is, locator elements  118  establish a selected circumferentially alignment of end ring  88  relative to stator core  30 . 
     In a non-limiting example, inner surface  110  of end ring  88  includes a plurality of coolant spray notches  130  that align with one of channels  44  and  48  and or the coolant passages defined by first and second cooling channel portions  72  and  73 . The coolant spray notches  130  guide coolant onto end turn  32  as shown in  FIG. 8 . In this manner, not only does the coolant reduce operating temperatures of stator core  30  but also lowers stator end turn temperatures. It should be understood that while the coolant spray notches are described as being on inner surface  110  of end ring  88 , additional coolant notches (not shown) are provided on end ring  87 . 
     In accordance with a non-limiting example shown in  FIG. 9 , coolant  100  enters coolant inlet  22  and a substantially bifurcates into a first coolant flow portion  108  and a second coolant flow portion  110 . First coolant flow portion  108  enters coolant flow path  50  and flows circumferentially clockwise around the stator  26  within first and second pluralities of channels  44  and  48 . Second coolant flow portion  110  flows circumferentially counter-clockwise about stator  26  within first and second pluralities of channels  44  and  48 . 
     Upon reaching channels  72  and  73 , a portion of first and second coolant flows  108  and  110  flows axially across stator  26 . At this point, coolant  100  exits channels  72  and  73  at each of first axial end  28  and second axial end  30  and is sprayed onto corresponding ones of first and second end turns  32  and  34 . The coolant continues to flow around and through first and second end turns  32  and  34  and drops down to the bottom (not separately labeled) of housing  14 . Coolant  100  collects at the bottom of housing  14  and drains through coolant outlet  25 . 
     In one non-limiting example, illustrated in  FIGS. 1 and 9  coolant inlet  22  is located axially inwardly of first and second axial end  28  and  30 . Coolant outlet  25  is disposed axially outwardly of first and second axial ends  28  and  30 . In addition, electric motor  10  includes a rotor (not shown) having a hollow rotor shaft (also not shown) that may carry coolant which is sprayed onto an inner diameter  120  ( FIG. 1 ) stator  26 . 
     At this point, it should be understood that the exemplary embodiments describe a stator that includes radially outwardly extending projections, each including circumferentially extending portions that create a tortuous or serpentine cooling channel. With this arrangement, additional surface area of the stator laminations is exposed to cooling fluid thereby enhancing heat shedding capacity. The heat shedding capacity may be increased by as much as 50% or greater compared to existing systems. Further, the increased surface area of the stator laminations provides increased flux carrying capacity of the stator that may increase performance by as much as 5%. Thus, not only does the present invention provide additional cooling but also increases an overall operational efficiency of the electric motor. 
     The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. 
     While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.