Abstract:
A high-speed sleeveless rotor for an electric machine is provided. The rotor includes a shaft rotatable about a longitudinal axis, and a rotor core circumscribing at least a portion of the shaft wherein the rotor core includes an axially oriented slot. The slot includes a radially outer slot opening, a radially inner slot floor, and a slot sidewall extending therebetween. The slot floor includes a topstick attachment member extending radially outward from the slot floor and configured to engage a topstick positioned in the slot opening and the slot sidewall includes a shoulder configured to engage the topstick, preventing radially outward movement of the topstick.

Description:
BACKGROUND OF THE INVENTION 
     The field of the invention relates generally to aircraft engine synchronous machines, and more specifically, to an apparatus and system for a sleeveless high-speed engine starter/generator rotor. 
     At least some known synchronous machine rotors rotate at high rate of rotational velocity. Centrifugal forces acting on components housed in the rotor are related to a mass of the component, a rotating speed of the rotor, and on a distance to the component from a center of rotation of the rotor. To contain the rotor components within the rotor envelope, known rotors use a sleeve into which the stacked laminations and components of the rotor are pressed. The rotor containment sleeve maintains the rotor stresses at acceptable levels. However, the rotor containment sleeve also increases an assembly weight of the rotor and hence the synchronous machine and increases the distance of the airgap between the main rotor and the stator decreasing the magnetic efficiency of the machine. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, a high-speed sleeveless rotor for an electric machine includes a shaft rotatable about a longitudinal axis, and a rotor core circumscribing at least a portion of the shaft wherein the rotor core includes an axially oriented slot. The slot includes a radially outer slot opening, a radially inner slot floor, and a slot sidewall extending therebetween. The slot floor includes a topstick attachment member extending radially outward from the slot floor and configured to engage a topstick positioned in the slot opening and the slot sidewall includes a shoulder configured to engage the topstick, preventing radially outward movement of the topstick. 
     In another embodiment, a high-speed sleeveless rotor for an electric machine includes a plurality of laminations each having an outer peripheral edge stacked face-to-face along a rotor shaft forming a rotor core having an outer peripheral surface including the edges of the plurality of laminations. The rotor also includes a plurality of axial slots spaced at a predetermined interval in the circumferential direction of the rotor core, each axial slot is closed by a topstick extending at least partially along a length of the slot. Each axial slot includes an engagement surface configured to engage a radially outer lip of the topstick, a side wall extending radially inwardly toward a slot floor, and an attachment member extending radially outward from the slot floor. The attachment member is configured to engage at least one of the topstick and a topstick wedge such that centrifugal forces generated in one or more components positioned within the slot are shared between the attachment member and the engagement surface. 
     In yet another embodiment, a lamination for a laminated core of an electric machine includes a unitary planar body that includes an outer peripheral edge, an inner peripheral edge spaced radially from the outer peripheral edge, and a plurality of openings that extend through the body from the outer peripheral edge radially inwardly such that the openings are arcuately spaced about the body. The openings each include a slot floor edge between the outer peripheral edge and the inner peripheral edge. The slot floor edge includes a topstick attachment member extending radially outward therefrom and configured to engage at least one of a topstick and a topstick wedge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-6  show exemplary embodiments of the rotor and lamination described herein. 
         FIG. 1  is a schematic electrical diagram of an engine starter/generator (ES/G) assembly; 
         FIG. 2  is a perspective view of the rotor assembly shown in  FIG. 1 ; 
         FIG. 3  is an axial view of a portion of a main rotor lamination of the plurality of laminations shown in  FIGS. 1 and 2 ; 
         FIG. 4  is an axial view of a portion of main rotor lamination of the plurality of laminations shown in  FIGS. 1 and 2  in accordance with another exemplary embodiment of the present invention; 
         FIG. 5  is an axial view of a portion of main rotor lamination of the plurality of laminations shown in  FIGS. 1 and 2  in accordance with still another exemplary embodiment of the present invention; and 
         FIG. 6  is an axial view of a portion of main rotor lamination of the plurality of laminations shown in  FIGS. 1 and 2  in accordance with still another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description illustrates embodiments of the invention by way of example and not by way of limitation. It is contemplated that the invention has general application to rotating machinery in industrial, commercial, and residential applications. 
     As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
       FIG. 1  is a schematic electrical diagram of an engine starter/generator (ES/G) assembly  100  including a main generator  102 , a permanent magnet generator (PMG)  104 , and an exciter  106  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, ES/G assembly  100  includes a rotor assembly  106  comprising a shaft  108 . 
     In the exemplary embodiment, PMG  104  includes a PMG stator  110  and a PMG rotor  112 . PMG stator  110  supplies electrical power to a generator voltage regulator (GVR)  114 . AC voltage is induced in stator windings  116  by rotating permanent magnets  118  of the PMG  104 . GVR  114  circuitry rectifies and modulates an output  120  of PMG  104 . An output  122  of GVR  114  is fed back to an exciter field winding  124 , generating an AC voltage on an exciter rotor  126 , which causes a current flow. Exciter  106  is a brushless, synchronous machine with a stator  128  and three-phase wound exciter rotor  126 . Exciter stator  128  has a three-phase winding during a start mode and a DC winding during a generate mode. The magnitude of AC voltage output of exciter  106  is proportional to the DC excitation current on field winding  124  and a rotational speed of rotor  126 . 
     An AC output  130  of rotor  126  is rectified with a full wave bridge of a plurality of diode rectifiers  132 , mounted axially inside shaft  108  for direct contact oil cooling and low inertial forces. A DC output  134  from diode rectifiers  132  supplies field current to main generator  102 . 
     Main generator  102  includes a wound multiple-pole main rotor  136  and a star-connected  3 Ø main stator  138 . The magnitude of a voltage output  140  of main stator  138  is proportional to DC output  134  current supplied by the exciter rotor  126  and a rotational speed of main rotor  136 . The DC excitation voltage of output  122 , supplied to field winding  124  determines a magnitude of the output power from main generator  102 . 
     The electrical output  140  of main stator  138  of main generator  102  is fed into a respective inverter/converter controller (ICC)  142 . During continuous power generating modes, AC output  140  (120 Vac) of main generator  102  is rectified into for example, 270 Vdc for distribution. 
     Rotor  106  is a sleeveless high speed rotor design capable of a rotational speed greater than 24,000 rpm. Being sleeveless, an outer peripheral edge  144  of a plurality of laminations  146  that are stacked together to form a rotor core  148  is also an outer peripheral extent  150  of rotor  136 . 
       FIG. 2  is a perspective view of rotor assembly  106  (shown in  FIG. 1 ) in accordance with an exemplary embodiment of the present invention. As shown in  FIG. 1 , rotor assembly  106  includes exciter rotor  126 , PMG rotor  112 , and main rotor  136  mounted on common shaft  108 . In the exemplary embodiment, shaft  108  is hollow and forms a conduit  200  for cooling oil and a mounting space for, for example, diode rectifiers  132 . In the exemplary embodiment, main rotor  136  includes an onboard portion of a rotor oil cooling system (not shown in  FIG. 2 ). The onboard portion includes oil piping connections  202  configured to couple respective main rotor oil cooling tubes (not shown in  FIG. 2 ) to shaft  108 . 
       FIG. 3  is an axial view of a portion of a main rotor lamination  300  of the plurality of laminations  146  (shown in  FIGS. 1 and 2 ) in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, lamination  300  includes a substantially circular cross-section of which only a portion is shown. Lamination  300  includes outer peripheral edge  144  (shown in  FIG. 1 ) that forms a part of outer peripheral extent  150  of rotor  136  when rotor  136  is fully assembled. It should be noted that rotor  136  does not include a sleeve that is used in prior art high-speed rotors to reduce the stresses of containing the centrifugal forces acting on the rotor that must be otherwise accommodated by the laminations. 
     Lamination  300  includes a center bore  302  that circumscribes shaft  108  when lamination  300  is installed on shaft  108 . Lamination  300  includes a plurality of copper bar apertures  304  circumferentially spaced about edge  144 . In one embodiment, apertures  302  are open to edge  144  and in various other embodiments, apertures  304  are closed to edge  144 . 
     Lamination  300  further includes a main slot  306  for carrying various rotor borne components of ES/G assembly  100 . For example, main slot  306  is sized and configured to house main rotor windings  308 , main rotor oil tubes  310 , main rotor winding wedges  312 , a slot liner  314 , and a main rotor topstick  316 . 
     Main slot  306  includes an opening  318  and a slot floor  320 . In contrast to prior art rotor slots, slot floor  320  includes an attachment member  322  that extends radially outward from slot floor  320  at least partially into slot  306 . In the exemplary embodiment, attachment member  322  includes an extension  324  between slot floor  320  and attachment member  322 . During operation, topstick  316  secures the various rotor borne components during rotor rotation. Topstick  316  is secured to main rotor  136  using a topstick engagement surface  326  configured to engage a complementary engagement surface  328  on lamination  300 . Additionally, topstick  316  is secured to main rotor  136  using an attachment slot  330  formed in a radially inner side of topstick  316  and attachment member  322 . In the exemplary embodiment, attachment member  322  is dovetail-shaped and attachment slot  330  is complementarily shaped to engage attachment member  322 . Restraining topstick  316  using an engagement method proximate the periphery of lamination  300  and restraining topstick  300  using an attachment method at radially inner attachment member  322  permits operating main rotor  136  at relatively high rotational speeds without using a rotor sleeve. 
       FIG. 4  is an axial view of a portion of main rotor lamination  300  of the plurality of laminations  146  (shown in  FIGS. 1 and 2 ) in accordance with another exemplary embodiment of the present invention. In the exemplary embodiment, lamination  300  includes a substantially circular cross-section of which only a portion is shown. Lamination  300  includes outer peripheral edge  144  (shown in  FIG. 1 ) that forms a part of outer peripheral extent  150  of rotor  136  when rotor  136  is fully assembled. 
     Lamination  300  includes center bore  302  that circumscribes shaft  108  when lamination  300  is installed on shaft  108 . Lamination  300  includes plurality of copper bar apertures  304  circumferentially spaced about edge  144 . In one embodiment, apertures  302  are open to edge  144  and in various other embodiments, apertures  304  are closed to edge  144 . 
     Lamination  300  further includes main slot  306  for carrying various rotor borne components of ES/G assembly  100 . For example, main slot  306  is sized and configured to house main rotor windings  308 , main rotor oil tubes  310 , main rotor winding wedges  312 , slot liner  314 , and a main rotor topstick  400 . In the exemplary embodiment, a main rotor topstick wedge  402  includes a first securement member  404  configured to couple to attachment member  322  and a second securement member  406  configured to couple to main rotor topstick  400 . 
     Main slot  306  includes opening  318  and slot floor  320  that includes attachment member  322 . Attachment member  322  extends radially outward from slot floor  320  at least partially into main slot  306 . Topstick  400  is secured to main rotor  136  using main rotor topstick wedge  402  and attachment member  322 . In the exemplary embodiment, main rotor topstick wedge  402  is secured to main rotor  136  using first securement member  404  formed in a radially inner side of main rotor topstick wedge  402 . In the exemplary embodiment, attachment member  322  is dovetail-shaped and first securement member  404  is complementarily shaped to engage attachment member  322 . In an alternative embodiment, attachment member  322  comprises for example, a slot and first securement member  404  is complementarily shaped to the slot to engage attachment member  322 . Additionally, attachment member  322  may comprise a fastener coupled to a complementary insert formed or attached to rotor  136 . Restraining topstick  316  using the above described attachment method at radially inner attachment member  322  permits operating main rotor  136  at relatively high rotational speeds without using a rotor sleeve. 
       FIG. 5  is an axial view of a portion of main rotor lamination  300  of the plurality of laminations  146  (shown in  FIGS. 1 and 2 ) in accordance with still another exemplary embodiment of the present invention. In the exemplary embodiment, main rotor topstick  500  is a single unitary piece that substantially combines the structures of main rotor topstick wedge  400  (shown in  FIG. 4 ) and main rotor topstick  400  (shown in  FIG. 4 ). Main rotor topstick  500  is secured to rotor  136  using attachment member  322  and a securement member  502  that is substantially similar to securement member  404  (shown in  FIG. 4 ). Main rotor topstick  500  includes a topstick engagement surface  526  configured to engage a complementary engagement surface  528 . Accordingly, main rotor topstick  500  is retained within rotor  136  using two independent methods such that centrifugal forces acting on components in slot  306  are shared between attachment member  322  and engagement surface  528 , permitting rotor  136  to be fabricated without a sleeve. 
       FIG. 6  is an axial view of a portion of main rotor lamination  300  of the plurality of laminations  146  (shown in  FIGS. 1 and 2 ) in accordance with still another exemplary embodiment of the present invention. In the exemplary embodiment, main rotor topstick  600  is a single unitary piece that is secured to rotor  136  using attachment member  322  and a securement member  602 . In the exemplary embodiment shown in  FIG. 6 , attachment member  322  comprises an axial slot extending radially inwardly from a slot floor  604  and securement member  602  comprises a tab extending radially inwardly from securement member  602  to engage the slot. Main rotor topstick  600  includes a topstick engagement surface  626  configured to engage a complementary engagement surface  628 . Accordingly, main rotor topstick  600  is retained within rotor  136  using two independent methods such that centrifugal forces acting on components in slot  306  are shared between attachment member  322  and engagement surface  628 , permitting rotor  136  to be fabricated without a sleeve. 
     The above-described embodiments of a rotor and a lamination for a high-speed sleeveless rotor provides a cost-effective and reliable means for fabricating a high speed rotor that transfers the centrifugal forces acting on a rotor slot topstick to additional areas reducing the concentrated forces in one area. More specifically, the rotor and a lamination described herein facilitate reducing a weight of the rotor by eliminating the need for a rotor sleeve. In addition, the above-described rotor and a lamination facilitate securing the topstick in the rotor slots by providing additional areas of support for the topstick. As a result, the rotor and a lamination described herein facilitate improving the magnetic efficiency of the rotor field windings and the weight of the rotor in a cost-effective and reliable manner. 
     An exemplary rotor and a lamination for facilitate improving the magnetic efficiency of the rotor field windings and the weight of the rotor are described above in detail. The apparatus illustrated is not limited to the specific embodiments described herein, but rather, components of each may be utilized independently and separately from other components described herein. Each system component can also be used in combination with other system components. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.