Abstract:
The present invention is generally concerned with an inductance assembly that is so configured and sized as to be inserted inside the cooling assembly of an electric machine to thereby decrease the overall volume of the machine.

Description:
PRIORITY CLAIM 
   This application claims the benefit of U.S. Provisional Patent Application filed on Sep. 13, 2006 Ser. No. 60/844,087, the specification of which is expressly incorporated herein, in its entirety, by reference. 

   FIELD 
   The present invention relates to electric machines. More specifically, the present invention is concerned with electric machines provided with an inductance assembly mounted therein. 
   BACKGROUND 
   Electric machines are well known in the art. They usually have a fixed stator and a rotating rotor. Generally the stator is external and the rotor is rotatably mounted inside the stator, coaxially therewith. 
   In some electric machines, the stator is internal and the cylindrical rotor is coaxially mounted outside the stator. These machines will be referred herein as internal stator electric machines. 
   Some of these electric machines are powered by battery and use a boost circuit to selectively increase the voltage of the battery. This is interesting in many applications, for example to ensure that the voltage presented to the load is constant even when the voltage from the battery decreases. 
   Such a boost circuit is schematically illustrated in  FIG. 1 . In this circuit, an inductance, a capacitor, two transistor and two diodes are used to increase the voltage of the battery as presented to the load. This circuit will not be described in greater details herein since it is believed to be understood by one skilled in the art of electric machines control. 
   It is to be noted that in many applications the size of the inductance is important since it must carry strong currents. Also, the inductance generates heat that must be dissipated for adequate operation of the electric machine. 
   OBJECTS OF THE INVENTION 
   An object of the present invention is therefore to provide an inductance assembly for an electric machine 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
     In the appended drawings: 
       FIG. 1  is a schematic circuit of a boost circuit; 
       FIG. 2  is a perspective view of an inductance assembly according to a first illustrative embodiment of the present invention mounted inside the internal stator of an electric machine, the coils of the inductance assembly being omitted for illustration purpose; 
       FIG. 3  is a perspective view of a coil to be inserted in the inductance assembly of  FIG. 2 ; 
       FIG. 4  is a top plan view of the inductance assembly of  FIG. 2 , the cooling assembly of the electric machine being shown in dashed lines; 
       FIG. 5  is a side elevational view of the inductance assembly of  FIG. 2 , the cooling assembly of the electric machine being shown in dashed lines; 
       FIG. 6  is a perspective view of a retaining element used in the inductance assembly of  FIG. 2 ; 
       FIG. 7  is a perspective view of an inductance assembly according to a second illustrative embodiment of the present invention mounted inside the internal stator of an electric machine, the coils of the inductance assembly being omitted for illustration purpose; 
       FIG. 8  is a top plan view of the inductance assembly of  FIG. 7 , the cooling assembly of the electric machine being shown in dashed lines; 
       FIG. 9  is a side elevational view of the inductance assembly of  FIG. 7 , the cooling assembly of the electric machine being shown in dashed lines; 
       FIG. 10  is a perspective view of a retaining element used in the inductance assembly of  FIG. 7 ; 
       FIG. 11  is a top plan view of a cooling assembly in which the inductance assembly of  FIG. 7  is mounted; 
       FIG. 12  is a sectional view taken along line  12 - 12  of  FIG. 11 ; 
       FIG. 13  is a bottom perspective view of the cooling assembly of  FIG. 11 ; 
       FIG. 14   11  is a top plan view of an alternate cooling assembly in which the inductance assembly of  FIG. 7  is mounted; and 
       FIG. 15  is a sectional view taken along line  15 - 15  of  FIG. 14 . 
   

   DETAILED DESCRIPTION 
   In accordance with an illustrative embodiment of the present invention, there is provided an inductance assembly to be mounted in a cooling assembly having a generally cylindrical inner surface; the inductance assembly comprising: 
   at least two longitudinal body portions each having a generally semi-cylindrical outer surface so configured as to be mounted to the generally cylindrical inner surface of the cooling assembly; each body portion being provided with a longitudinal central arm defining first and second longitudinal channels; 
   at least one coil provided with first and second longitudinal leg portions provided between first and second head portions; the first leg portion being so configured as to be inserted in the first longitudinal channel and the second leg portion being so configured as to be inserted in the second longitudinal channel; and 
   at least one clip so mounted between the at least two longitudinal body portions as to bias the generally semi-cylindrical outer surfaces of the at least two longitudinal body portions to the generally cylindrical inner surface of the cooling assembly. 
   According to another aspect of the present invention, there is provided an inductance assembly to be mounted in an electric machine provided with an internal stator having a generally cylindrical inner surface; the inductance assembly comprising: 
   a cooling assembly having a generally cylindrical outer surface configured and sized to be inserted in the internal stator, and a generally cylindrical inner surface; 
   at least two longitudinal body portions each having a generally semi-cylindrical outer surface so configured as to be mounted to the generally cylindrical inner surface of the cooling assembly; each body portion being provided with a longitudinal central arm defining first and second longitudinal channels; 
   at least one coil provided with first and second longitudinal leg portions provided between first and second head portions; the first leg portion being so configured as to be inserted in the first longitudinal channel and the second leg portion being so configured as to be inserted in the second longitudinal channel; and 
   at least one clip so mounted between the at least two longitudinal body portions as to bias the generally semi-cylindrical outer surfaces of the at least two longitudinal body portions to the generally cylindrical inner surface of the cooling assembly. 
   The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one”. Similarly, the word “another” may mean at least a second or more. 
   As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps. 
   Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of illustrative embodiments thereof, given by way of example only with reference to the accompanying drawings. 
   Generally stated, an inductance assembly according to an illustrative embodiment of the present invention is so configured and sized as to be inserted inside the internal stator of an electric machine and securely mounted therein. 
   Turning now to  FIG. 2 to 6  of the appended drawings, an inductance assembly  20  according to a first illustrative embodiment of the present invention will be described. 
     FIG. 2  illustrates a portion of the inductance assembly  20  mounted inside an internal stator  22  of an electric machine (not shown). More specifically, the inductance assembly  20  is mounted inside a generally tubular cooling assembly  24 , itself mounted inside the generally tubular internal stator  22 . 
   The inductance assembly  20  includes two body portions  26  and  28 , a plurality of coils  30  inserted in the body portions  26  and  28  (see  FIGS. 3 ,  4  and  5 ) and two clips  32 ,  34  maintaining the inductance assembly  20  in the cooling assembly  24 . 
   It is to be noted that the coils  30  are not illustrated in  FIG. 2  to better show the features of the body portions  26  and  28 . It is also to be noted that since the body portions  26  and  28  are identical, only the body portion  26  will be described hereinbelow, for concision purpose. 
   As can be better seen from  FIG. 2 , the body portion  26  is generally E-shaped, having a semi-cylindrical outer surface  36  so configured and sized as to adequately contact the internal cylindrical surface  38  of the cooling assembly  24 . The body portion  26  includes a central arm  40  defining two stepped longitudinal channels  42  and  44  so configured as to receive the coils  30 . 
   Turning now to  FIG. 3  of the appended drawings, an illustrative coil  30  will be described. The coil  30  includes many turns of rectangular wire each provided with first and second leg portions  46  and  48  integrally mounted between heads  50  and  52  to yield a continuous coil. 
   It is to be noted that in the illustrative embodiment of the inductance assembly, there are four different coils  30  used to form the inductance inserted in each of the body portions  26  and  28  (only one shown in  FIG. 3 ). These four coils  30  are so configured and sized as to be inserted inside each other. It will be understood that the number of coils  30  used may vary. 
     FIGS. 4 and 5  illustrate the four coils  30   a,    30   b,    30   c  and  30   d,  coil  30   a  being the smallest and coil  30   d  being the largest. 
   As better seen in  FIG. 4 , once the coils  30   a - 30   d  have been inserted in the longitudinal channels  42  and  44 , two stoppers  54  and  56  are slidably engaged in the triangular notches  58  (see  FIG. 2 ) facing each others in the channels to maintain the coils in place. 
   Also seen on this figure are key  58  and keyway  60  arrangements provided between the external surface  36  of the body portion  26  and the internal surface  38  of the cooling assembly. The key and keyway arrangement is provided to both prevent rotation of the inductance assembly  20  in the cooling assembly  24  and to properly position the body portions  26  and  28  during assembly. 
     FIG. 4  also shows that the external surface  36  of the body portions  26  and  28  includes chamfered edges  62  and  64  to allow the insertion of the two clips  32  and  34  between the body portions  26  and  28 . 
   The clip  32  is illustrated in  FIG. 6 . It is to be noted that clip  34  is identical to clip  32 . Clip  32  is made of resilient material and has a longitudinal flat body  66  provided, at both ends, with curved spring portions  68 . Therefore, once inserted in the cooling assembly  24  between the two body portions  26  and  28 , the two clips  32  and  34  will bias the external surfaces  36  of the body portions towards the internal surface  38  of the cooling assembly  24 . 
   It is believed to be within the reach of one skilled in the art to determine the number of coils  30  used to form the inductance and the method of interconnection between the coils depending on the application of the inductance assembly. 
   It will also be apparent to those skilled in the art that since there is adequate contact between the external surface of the body portions  26  and  28  and the internal surface of the cooling assembly  24 , the heat generated by the coils  30  will be collected by the cooling assembly  24  and removed from the electric machine. 
   Turning now to  FIGS. 7 to 10  of the appended drawings, an inductance assembly  100  according to a second illustrative embodiment of the present invention will be described. It is to be noted that since the inductance assembly  100  is very similar to the inductance assembly  20  described hereinabove with reference to  FIGS. 2 to 6 , only the differences therebetween will be described hereinbelow. 
   Generally stated the main difference between the two inductance assemblies relates to the manner used to mount them inside the cooling assembly  24 . 
   Indeed, while clips  32 ,  34  provided with respective spring portions are used for the inductance assembly  20  (see  FIG. 6 ), two complementary wedge-shaped blocks  102  and  104  (see  FIG. 10 ) are used to bias the body portions  106  and  108  apart from one another. The blocks  102  and  104  are advantageously made of non-magnetic material such as heat resistant plastic or aluminum alloy. 
   It is to be noted that while two sets of the complementary wedge-shaped blocks are used in the inductance assembly of  FIG. 7 , a third set of blocks (see  FIGS. 11 and 12 ) could be used between the central arms  40  of the body portions. 
   Also the external surface  110  of the body portions  106  and  108  may be completely semi-cylindrical since the chamfered edges  62  and  64  (see  FIG. 4 ) that allow the two clips  32  and  34  to be inserted between the body portions are not required. 
   Turning now to  FIGS. 11 to 16  of the appended drawings, two alternate cooling assemblies in which the inductance assembly  100  illustrated in  FIG. 7  is inserted will be described. 
   Referring more specifically to  FIGS. 11 to 13 , a cooling assembly  200  will be described. The cooling assembly  200  is made of a heat conducting material such as aluminum alloy and conventionally includes a cooling fluid inlet  202 , a cooling fluid outlet  204  and a cooling channel (not shown) interconnecting the inlet  202  and the outlet  204 . 
   As can be better seen from  FIG. 12 , the cooling assembly includes a generally cylindrical body  206  provided with an internal projection  208  defining an internal shoulder so configured as to receive a cradle  210 . The cradle  210  has a generally cylindrical outer surface  212  conforming to the generally cylindrical internal surface of the body  206 . The internal surface  214  has a generally C-shaped cross section and is provided with a shoulder  216  that is so configured as to receive the inductance assembly  100  while the coils thereof are safely distant from the cradle  210 . The shoulder  216  acting as a longitudinal stop for the inductance assembly  100 . 
     FIG. 13  illustrates that the projection  208  is not continuous and that fasteners  218  are used to mount the cradle  210  to the body  206 . 
   Referring more specifically to  FIGS. 14 to 16 , a cooling assembly  300  will be described. Again, the cooling assembly  300  is made of a heat conducting material such as aluminum alloy and conventionally includes a cooling fluid inlet  302 , a cooling fluid outlet  304  and a cooling channel (not shown) interconnecting the inlet  302  and the outlet  304 . The cooling assembly  300  is very similar to the cooling assembly  200  described hereinabove. Accordingly, only the differences therebetween will be describes herein. 
   As can be better seen from  FIG. 15 , the body  306  of the cooling assembly  300  is a one piece molded element including a cradle portion similar in shape to the separated cradle  210  of  FIG. 12 . Again a shoulder  308  receives the inductance assembly  100  in an appropriate position since it acts as a longitudinal stop for the inductance assembly  100 . 
   It is to be noted that while rectangular wire is used to form the coils  30  illustrated herein, other wire cross-sections could be used. 
   It is to be noted that during the assembly of the inductance assembly, the body portions can be independently impregnated with resin once the coils  30  have been inserted therein. Of course, both body portions could be impregnated at the same time. 
   It is also to be noted that while the inductance assemblies illustrated hereinabove include two body portions, one skilled in the art could design an inductance assembly according to the principles of the present invention using more than two body portions. 
   It is also to be noted that insulation film (not shown) can be provided between the coils and the body portions. One skilled in the art is believed to be in a position to determine an adequate insulation film. 
   It is also to be noted that an adhesive (not shown) may be provided between the body portions and the cooling assembly. One skilled in the art is believed to be in a position to determine an adequate adhesive. 
   It is to be understood that the invention is not limited in its application to the details of construction and parts illustrated in the accompanying drawings and described hereinabove. The invention is capable of other embodiments and of being practiced in various ways. It is also to be understood that the phraseology or terminology used herein is for the purpose of description and not limitation. Hence, although the present invention has been described hereinabove by way of illustrative embodiments thereof, it can be modified, without departing from the spirit, scope and nature of the subject invention.