Abstract:
A motor driven assembly includes a motor having a motor inlet and a motor outlet, a shaft, and a rotor spaced radially outwards from the shaft. A cooling flow passage is located between the shaft and the rotor. The cooling flow passage fluidly connects the motor inlet and the motor outlet. A compressor is in fluid communication with the motor outlet. The compressor includes a compressor outlet that is in fluid communication with the motor inlet.

Description:
RELATED APPLICATION 
     This is a divisional application of U.S. patent application Ser. No. 12/843,352, filed on Jul. 26, 2010, which is a divisional application of U.S. Pat. No. 7,791,238. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to motor driven machinery and, more particularly, to motor driven turbo machinery with an internal cooling flow arrangement. 
     Typical motors in motor driven turbo assemblies, such as a motor driven compressor for moving air in an aircraft air conditioning system, include a rotational rotor that rotates about a motor shaft and a stator spaced radially outward of the rotational rotor. The design desire for the aircraft industry has been toward motors of smaller physical size, which provide increased power. As a result, progressively smaller motors are being driven at progressively higher rotational speeds. The combination of higher rotational speeds and smaller size results in significant heat generation, which may reduce magnetization of the rotational rotor and over a prolonged time period may ultimately result in motor or compressor failure. 
     One possible solution to heat generation in the motor is utilizing airflow through the space between the rotational rotor and the stator to communicate heat away from the motor. In selected conventional motor driven compressor assemblies, an internal portion of the motor is fluidly connected to an inlet port of the compressor. The compressor evacuates the internal portion of the motor during operation. Air evacuated from the motor passes through the space between the rotational rotor and the stator. The size of the space however, has decreased with the decreasing size of the motors. As a result, the airflow through the space is insufficient to provide effective thermal management of the motor. 
     Accordingly, there is a need for a motor driven assembly having an internal cooling flow arrangement that provides effective thermal management of a relatively small electric motor driven turbo machine. 
     SUMMARY OF THE INVENTION 
     An example motor driven assembly includes a motor having a motor inlet and a motor outlet, a shaft, and a rotor spaced radially outwards from the shaft. A cooling flow passage is located between the shaft and the rotor. The cooling flow passage fluidly connects the motor inlet and the motor outlet. A compressor is in fluid communication with the motor outlet. The compressor includes a compressor outlet that is in fluid communication with the motor inlet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows. 
         FIG. 1  is a schematic view of an example thermal management system; 
         FIG. 2  is a schematic view of one embodiment of a motor driven assembly of the present invention; 
         FIG. 3  is a schematic view of one embodiment of a cooling flow passage between a motor rotor and a motor shaft; 
         FIG. 4  is a cross-sectional view of the fins within the cooling flow passage shown in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of sub-passages between the fins within the cooling flow passage and secondary flow pattern; 
         FIG. 6  is a perspective view of one configuration of fins within the cooling flow passage; 
         FIG. 7  is a perspective view of another configuration of fins within the cooling flow passage; 
         FIG. 8  is a cross-sectional view of a rounded profile fin; 
         FIG. 9  is a cross-sectional view of a tapered profile fin; and 
         FIG. 10  is a perspective view of one embodiment of a motor rotor having a sleeve with radially extending fins. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  schematically illustrates selected portions of a thermal management system  10  that includes a motor driven assembly  12  for supplying pressurized air to a space  14 , such as an aircraft cabin. The motor driven assembly  12  includes a motor  16 , such as a permanent magnet motor, that drives a compressor  18 . The compressor  18  receives air from an outside source through outside source inlet  19  (such as unpressurized ram air or cabin air) and the motor  16 , compresses the air, and circulates the compressed air to the space  14 . 
     The motor  16  includes a first cooling flow passage  20  and a second cooling flow passage  22  that each receive air to provide internal cooling of the motor  16 . The first cooling flow passage  20  is connected to a first motor inlet  24  and the second cooling flow passage  22  is connected to a second motor inlet  26 . The first cooling flow passage  20  and the second cooling flow passage  22  are each fluidly connected to the compressor  18  and supply air to the compressor  18 . 
     A portion of the air compressed in the compressor  18  is diverted out of a compressor outlet  28  to a heat exchanger  30 . The heat exchanger  30  cools the compressed air before the air circulates into the first motor inlet  24  to cool the motor  16 . The second motor inlet  26  receives air from the environment surrounding the motor driven assembly  12 , such as ram air. The flow of air through the first cooling flow passage  20  and the second cooling flow passage  22  removes heat from the motor  16  to provide the benefit of maintaining the motor  16  at a desirable operating temperature to prevent, for example, motor overheating. 
     Referring to  FIG. 2 , the motor  16  includes a shaft  40  mounted on a bearing  42  for rotation about an axis A. A motor rotor  44  is mounted on the bearing  42  for rotation with the shaft  40  about the axis A. The motor rotor  44  is spaced apart from the shaft  40  such that the first cooling flow passage  20  is between the shaft  40  and the rotor  44 . Air incoming through the first motor inlet  24  flows through a motor conduit  45 , through the bearing  42 , into the first cooling flow passage  20 , and into the compressor  18 . 
     The second cooling flow passage  22  is divided into two passages. A motor stator  46  is spaced radially outward from the motor rotor  44  such that a stator-rotor passage  48  is between the motor rotor  44  and the motor stator  46 . The motor stator  46  is spaced apart from a motor housing  50  such that a stator passage  51  is between the stator  46  and the motor housing  50 . Intake air from the second motor inlet  26  is divided and flows either through the stator-rotor passage  48  or stator passage  51  to a motor outlet  52 . 
     A vent valve  53  near the motor outlet  52  is selectively opened or closed to respectively vent air from the stator passage  51  to the surrounding environment or direct air to the motor outlet  52  for supply into the compressor  18 . If the vent valve  53  is open, less air will flow into the compressor  18 . If the vent valve is closed, more air will flow into the compressor  18 . The vent valve  53  controls the air flow through the stator passage  51  to selectively control air flow into the compressor  18 . 
     The shaft  40  extends from the motor housing  50  into the compressor  18  to drive a compressor rotor  55 . The compressor rotor  55  compresses air received from the external source and motor outlet  52  and conveys compressed air through a compressor outlet  54  to the space  14 . A bleed valve  56  near the compressor outlet  54  diverts a portion of the compressed air through a conduit  58  and into the heat exchanger  30 . The heat exchanger  30  cools the compressed air before the air is conveyed to the first motor inlet  24 . The heat exchanger  30  supplies cooled air to the first motor inlet  24 , which results in a significantly cooler air than ambient and a significant cooling effect. 
     The motor  16  receives air for internal cooling of the motor  16  from two different sources. The first motor inlet  24  receives air from the heat exchanger  30  through the compressor bleed valve  56  and the second motor inlet  26  receives air from the surrounding environment. The first cooling flow passage  20  receives air from the first motor inlet  24  to generally cool the motor rotor  44  and the second cooling flow passage  22  receives air from the second motor inlet  26  to generally cool the motor stator  46  and the rotor-stator gap  48 . Utilizing two different sources of cooling air provides the benefit of minimizing air pressure drop through the motor  16  (i.e., at the motor outlet  52 ). If the first cooling flow passage  20  is narrow and restricts air flow there through, there may be an undesirable pressure drop between the first motor inlet  24  and the motor outlet  53 . The air flow through the second cooling flow passage  22  from the second motor inlet  26  to the motor outlet  53 , however, provides additional air at the motor outlet  52  and minimizes the air pressure drop that might otherwise occur if only a single air inlet was utilized. 
     Referring to  FIG. 3 , the motor rotor  44  includes fins  68  that provide increased surface area (e.g., compared to a cylindrical, smooth surface) from which the motor rotor emits heat into the passing air. The fins  68  extend radially inward from an inner diameter  70  of the motor rotor  44  into the first cooling flow passage  20 . The fins  68  each include a base portion  72  and a fin end  74  preferably having a squared profile, as illustrated in  FIG. 4 . 
     The fins  68  are spaced apart from each other and include first sub-passages  76  between the fins  68 . The fins ends  74  are spaced radially from the shaft  40  such that a second sub-passage  78  is between the fins ends  74  and the shaft  40 . Each fin  68  extends in a length direction ( FIG. 3 ) approximately parallel to the rotational axis A such that the first cooling flow passage  20 , which includes the first sub-passages  76  and the second sub-passage  78 , extends approximately parallel to the shaft  40 . 
     Incoming air flow from the first motor inlet  24  passes through the bearing  42  ( FIG. 2 ) and into the first cooling flow passage  20 . The air enters the first sub-passages  76  and the second sub-passage  78  before entering the compressor  18 . The fins  68  provide a relatively large surface area from which the motor rotor  44  conducts heat to the air passing through the first cooling flow passage  20  to cool the motor  16 . During operation of the motor driven assembly  12 , air flowing in the first cooling flow passage  20  flows along the first sub-passage  76  and down into the second sub-passage  78 , as illustrated in  FIG. 5 . The air passing though the first sub-passage  76  and the second sub-passage  78  absorbs and carries away heat that the motor rotor  44  emits from the surfaces of the fins  68  and the shaft  40  to cool the motor  16 . Owing to the centrifugal force generated by the rotation of the motor rotor  44 , a secondary flow is produced in the airflow inside these fin channels. In addition to the flow in axial direction parallel to the motor rotor  44 , a counter-rotating vortex, or secondary air flow pattern  45 , is created in the airflow as shown in the  FIG. 5 . Additional heat transfer enhancement is achieved by this effect. 
     The fins  68  are preferably formed integrally with the motor rotor  44 , such as by electrical discharge machining. Alternatively, the fins  68  are formed separately and then bonded to an inner diameter  70  ( FIG. 3 ) of the motor rotor  44 . If formed separately, the fins  68  may alternatively be manufactured of a material different than that of the motor rotor  44 . This provides a benefit of selecting a material that has particularly tailored heat transfer properties, such as a material with a relatively high thermal conductivity. 
       FIG. 6  illustrates a perspective view of another motor rotor  44 ′ configuration. The motor rotor  44 ′ includes a rotor can  100  about a periphery  102  of rotor pieces  104 . Rotor pieces  104 , such as permanent magnets, are assembled on a rotor hub  106 . The rotor hub  106  includes a cylindrical opening  108   a  having a diameter D. The cylindrical opening  108   a  is parallel to the rotational axis A of the motor shaft  40 . 
     A sleeve  110  is received in the cylindrical opening  108   a  and includes a cylindrical opening  108   b  for receiving the motor shaft  40 . A plurality of fins  112  extend radially outward from a tubular base portion  114  of the sleeve  110 . Each fin  112  includes a fin end  116 . In the illustration, the fin ends  116  have a square profile, however, the fin end  116  profiles may alternatively be rounded, tapered, or other shape to achieve a desired cooling effect as described above. The spaces between the fins  112  form the first cooling flow passage  20 ′. 
     The sleeve  110  includes an outer diameter D O  that extends between opposite fin ends  116  and an inner diameter D I  that extends between opposite sides of a smooth inner surface  118  of the cylindrical opening  108   b  of the sleeve  110 . The size of the outer diameter D O  of the sleeve  110  is slightly smaller than the diameter D of the cylindrical opening  108   a . In a generally known assembly procedure for assembling tight fitting components together, the sleeve  110  is chilled to thermally contract the size of the diameter D O . The contraction allows the sleeve  110  to fit into the cylindrical opening  108   a . After being inserted, the sleeve  110  warms and thermally expands as it returns to ambient temperature to provide a tight fit between the sleeve  110  and the rotor hub  106 . 
     During operation of the motor  16 , the rotor pieces  104  transfer heat from to the rotor hub  106 . The rotor hub  106  transfers heat to the sleeve  110  through contact surfaces between the fin ends  116  and an inner surface  120  of the rotor hub  106 . The fins  112  and rotor hub  106  emit heat into the air flowing through the first cooling flow passage  20 ′ between the fins  112  to provide a cooling effect on the motor  16 . 
       FIG. 7  illustrates an alternate fin configuration to that shown in  FIGS. 4 and 6  in which the fins  68   a  are offset from one another to produce a discontinuous flow path through the first cooling flow passage  20 . Air flow enters a second sub-passage  76   a  between a first fin  180  and a second fin  182 . The air exits the second sub-passage  76   a  and flows into a forward surface  184  of a third fin  186 . The air flows around the forward surface  184  into second sub-passages  76   a ′ and  76   a ″ between fins  186 ,  188 , and  190 . This configuration provides the benefit of additional surface area, such as the forward surface  184 , from which the motor rotor  44  emits heat into the passing air. 
     Referring to another alternate configuration shown schematically in  FIG. 8 , post fins  68   b  are offset from one another to produce a discontinuous flow path similar to that shown in  FIG. 7 . The post fins  68   b , or extended surface portions, have a squared profile, however, the profile can be selected to achieve a desired cooling effect as will be described below. 
       FIG. 9  schematically illustrates an alternate fin profile in which the fins  68   c  include rounded profiles. The rounded profile fins  68   c  include a fin height H, a radius of curvature R, and a width dimension D R . The height H, radius R, and width D R  are selected based upon a desired cooling effect as described below. 
     Referring to  FIG. 10 , the fins  68   d  include tapered profiles. The tapered fins  68   d  include relatively flat fin ends  192  and angled surfaces  194  that extend from the fin ends  192  to a fin base  196 . 
     The geometry (e.g., size and shape) of the fins  68   a - d  are tailored to achieve a desired cooling effect in the motor  16 . The amount of heat that the motor rotor  44  transfers to air passing through the first cooling passage  20  generally corresponds to the amount of exposed surface area of the fins  68   a - d  in the first cooling flow passage  20 . In selecting the size and shape of the fins  68   a - d , the available air flow from the first motor inlet  24 , an expected air pressure drop across the first cooling flow passage  20 , and a desired amount of heat transfer from the motor rotor  44  may also be taken into consideration to achieve a desired cooling level. Given this description, one of ordinary skill in the art will be able to select a fin size and shape to meet their particular motor cooling needs. 
     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.