Abstract:
In an electric rotary machine, a stator, a metallic supporting member configured to support the stator, and a rotor are provided, the rotor is relatively rotatably supported with respect to the stator, a magnetic path is formed via a gap portion between the stator and the rotor to give a torque to the rotor, and a space section is provided to interrupt the magnetic path at a position of the metallic supporting member near to a magnetic pole of the stator facing the gap portion.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    (1) Field of the Invention 
         [0002]    The present invention relates to an electric rotary machine in which a magnetic circuit (or a magnetic path) is formed between a rotor and a stator, and, more specifically, relates to a technique in the electric rotary machine which prevents a reduction of a driving efficiency generated due to an overflow of the magnetic path from a naturally ideal position of the magnetic path. 
         [0003]    (2) Description of the Related Art 
         [0004]    An electric machine in which a stator in which coil windings are equipped is supported by means of a metallic supporting member is exemplified by a Japanese Patent Application Publication (tokouhyou) of PCT Application (whose international publication is WO 03/084027) No. 2005-522166 published on Jul. 21, 2005 which corresponds to a U.S. Pat. No. 6,765,327 issued on Jul. 20, 2004. 
         [0005]    The previously proposed electric rotary machine disclosed in the above-described Japanese Patent Application Publication houses a rotor and the stator in an internal spatial region of a case made of an aluminum alloy. Cooling fins are attached on an external of the case. The stator is attached in an inside of the case. The stator is laminated with a plurality of thin-plate steel plates and non electrically conductive nonferrous layers. The stator minimizes a loss due to an eddy current of a magnetic flux at the inside of the stator. Furthermore, the stator is partitioned by means of thirty-six (36) grooves in a peripheral direction of the stator. The stator has the same number of stator cores as that of the grooves. An electrically conductive coil winding is wound on each of the stator cores. Since the case described above is formed of the aluminum alloy having a high thermal conductivity, heat generated on the coil windings and stator cores can speedily be discharged through the external of the case while a rigidity of the electric rotary machine is secured. Thus, a cooling performance of the electric rotary machine described above becomes high. 
       SUMMARY OF THE INVENTION 
       [0006]    However, in the previously proposed electric rotary machine described in the BACKGROUND OF THE INVENTION, the following problem occurs. That is to say, magnetic fluxes from the rotor and from the stator pass the case having no relationship to a torque generation of the rotor. At this time, an eddy current loss of each magnetic flux occurs and a driving efficiency of the electric rotary machine becomes worsened. Suppose that the magnetic flux passing the case is called a leakage magnetic flux. Especially, in a case where a high-load driving is carried out with the magnetic fluxes from the rotor of the previously proposed electric machine and from the stator thereof enlarged, the leakage magnetic flux overflowed from a magnetic circuit (or a magnetic path) directly formed via a gap provided between the rotor and the stator becomes accordingly enlarged. As a result of this, its loss becomes non-negligibly large. 
         [0007]    Regarding the above-described problem, the inventors (applicants) of the present application performed a model analysis for a comparative example of an axial gap electric rotary machine and clarified a portion of the axial gap electric rotary machine on which the leakage magnetic flux is remarkably present. A result of this model analysis will be explained with reference to  FIGS. 9 through 11 .  FIG. 9  shows a partially cross sectioned perspective view of the comparative example of the axial gap electric rotary machine in which both of the rotor and the stator are arranged in an axial direction. In  FIG. 9 , a reference symbol A denotes a part of the rotor and a reference symbol B denotes a part of the stator. Rotor A and stator B are separately opposed by a slightly short distance from each other in the axial direction of the electric rotary machine. A clearance between rotor A and stator B is called a gap. Each of permanent magnets C is adhered onto a front surface of both front and rear surfaces of a circular plate-like rotor A which opposes against stator B via the gap. Then, permanent magnets C, C, - - - are arranged in a circumferential (peripheral) direction of rotor A. Stator cores D, D, - - - are attached onto stator B and these stator cores D, D, - - - are arranged in the circumferential (peripheral) direction of stator B. Coil windings E are wound on surroundings of respective stator cores D. It should be noted that part of one of coil windings E is shown in a section. An inner peripheral ring F is arranged at an inner part of stator cores D in a radial direction of stator B. An outer peripheral ring G is arranged at an outer part of stator cores D in the radial direction thereof. Then, thin-plate materials H, H, - - - extended in the radial direction connect these rings F, G together and serve to couple these inner and outer peripheral rings F, G to each other. Each of these rings F, G and thin-plate materials H is formed of a light metal such as aluminum or duralumin. These members F, G, H are united into one body to constitute a metallic supporting member. This metallic supporting member constitutes a framework of stator B and the electric rotary machine. A structural rigidity (or a structural strength) of the electric rotary machine is secured. Each stator core D on which coil winding E is wound is arranged between circumferentially and mutually abutting thin-plate material H, H and between rings F, G. A resin is filled on an outer periphery of each coil winding E to assure a fixing of each coil winding E between thin-plate H and rings F, G. In this electric rotary machine, the magnetic fluxes from stator cores D and from permanent magnets C form the magnetic path via the gap between rotor A and stator B. Thus, a torque is given to rotor A to rotate rotor A. 
         [0008]    In order to improve the driving efficiency of the electric rotary machine, it is ideal that all of the magnetic fluxes pass the gap between magnetic poles of each of stator cores D and each of permanent magnets C at a shortest distance and, in other words, the magnetic path is directly formed between rotor A and stator B. However, as an actual matter of fact, a part of the magnetic fluxes from stator cores D and permanent magnets C bypasses the gap and passes members of electric rotary machine except rotor A and stator B (such as members F, G, and H). The leakage magnetic fluxes overflowed from an ideal magnetic path generate the eddy current in the magnetic flux passing members except rotor A and stator B to be converted into heat. Thus, the driving efficiency is lowered. Hence, a reduction of the leakage magnetic flux is desirable in terms of the driving efficiency. 
         [0009]      FIG. 10  shows a perspective view of inner peripheral ring F and of outer peripheral ring G as viewed from an arrow-marked direction in  FIG. 9 . In  FIG. 10 , a distribution of a magnetic flux density of the leakage magnetic flux passing through inner peripheral ring F and outer peripheral ring G which are not the stator nor the rotor is divided into a plurality of zones on the magnetic flux density, when the axial gap electric rotary machine of the above-described comparative example is driven in an acceleration state. In  FIG. 10 , a zone  4  indicates a large magnetic flux density and the magnetic flux densities become smaller in an order of a zone  3 , a zone  2 , and a zone  1 . It should be noted that the magnetic flux density is not varied in a stepwise manner for each portion shown in a zone division but the magnetic flux density is distributed so as to be varied in continuous and progressive manners from a portion at which the magnetic flux density is relatively large to a portion at which the magnetic flux density is relatively small. 
         [0010]      FIG. 11  shows a distribution of eddy current densities caused by the leakage magnetic flux described above divided into a plurality of zones. In  FIG. 11 , a zone  4 ′ indicates a large eddy current density and the eddy current densities become smaller in an order of a zone  3 ′, a zone  2 ′, and a zone  1 ′. It should be noted that the eddy current density is not varied in a stepwise manner for each portion shown in the zone division but the eddy current density is distributed so as to be varied in continuous and progressive manners from a portion at which the eddy current density is relatively large to a portion at which the eddy current density is relatively small. As shown in  FIG. 11 , the eddy current density becomes larger as the portion of each member becomes nearer to the gap. In other words, the eddy current density becomes larger as the portion of each member becomes nearer to the magnetic pole of each stator core D which faces against the gap and to the magnetic pole of each permanent magnet C which faces the gap. 
         [0011]    It is, in view of the above-described actual circumstance and the result of the model analysis, to provide a technique for an electric rotary machine which can effectively prevent the leakage magnetic flux. 
         [0012]    According to one aspect of the present invention, there is provided an electric rotary machine comprising: a stator; a metallic supporting member configured to support the stator; and a rotor, the rotor being relatively rotatably supported to the stator, a magnetic path being formed via a gap portion between the stator and the rotor to give a torque to the rotor, and a space section being provided on a portion of the metallic supporting member near a magnetic pole of the stator facing the gap portion to interrupt the magnetic path. According to a structure of the electric rotary machine in the present invention, a space section has a large magnetic resistance and the magnetic flux becomes difficult to pass through the space section. Hence, the passage of the magnetic flux through the metallic supporting member can largely be eliminated. Thus, a generation of an eddy current can be suppressed and an undesirable temperature rise of the electric rotary machine can be reduced. In addition, the leakage of the magnetic flux from the magnetic path formed between the stator and the rotor via the gap can be eliminated and the magnetic path is formed to connect a magnetic pole of an armature provided on the stator to a magnetic pole or a salient pole of each permanent magnet installed on the rotor at a shortest distance. An improvement in the driving efficiency of the electric rotary machine and a large torque can be expected. When a large torque driving at which the magnetic flux density of the magnetic path becomes large is carried out, the effect of the suppression of the heat generation and the effect of the improvement in the driving efficiency can more remarkably be enjoyed. This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features. The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a longitudinal cross sectional view of a preferred embodiment of an electric rotary machine according to the present invention partially cut away with a plane including an axial line. 
           [0014]      FIG. 2  is a longitudinal cross sectional view of another preferred embodiment of the electric rotary machine according to the present invention partially cut away with the plane including the axial line. 
           [0015]      FIG. 3  is a perspective view of a case of the electric rotary machine in a still another preferred embodiment according to the present invention with the case partially broken. 
           [0016]      FIG. 4  is a perspective view of a part of the case of the electric rotary machine in a further another preferred embodiment according to the present invention with a part of the case broken. 
           [0017]      FIG. 5  is a cross sectional view of the part of the case shown in  FIG. 4  cut away along a line of A-A in  FIG. 4 . 
           [0018]      FIG. 6  is a cross sectional view of the part of the case shown in  FIG. 4  cut away along a line of B-B in  FIG. 4 . 
           [0019]      FIG. 7  is a perspective view of the case and an inner peripheral ring in the further other preferred embodiment of the electric rotary machine representing a result of analysis of a distribution of magnetic fluxes of the inner peripheral ring and the case in the further another preferred embodiment under the same condition as a model shown in  FIG. 9 . 
           [0020]      FIG. 8  is a perspective view of the case and the inner peripheral ring in the further other preferred embodiment of the electric rotary machine representing a result of analysis of a distribution of eddy current densities of the inner peripheral ring and the case in the further other preferred embodiment under the same condition as a model shown in  FIG. 9 . 
           [0021]      FIG. 9  is a partially cross sectioned perspective view of an analytical model which is a comparative example of an axial gap electric rotary machine in which a rotor and a stator are arranged in an axial direction to the present invention. 
           [0022]      FIG. 10  is a perspective view representing a magnetic flux density distribution of the inner peripheral ring and an outer peripheral ring in the analytical model shown in  FIG. 9 . 
           [0023]      FIG. 11  is a perspective view representing an eddy current density distribution of the inner peripheral ring and an outer peripheral ring in the analytical model shown in  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Reference will hereinafter be made to the drawings in order to facilitate a better understanding of the present invention. 
         [0025]      FIG. 1  shows a longitudinal cross sectional view of a stator in a preferred embodiment of an electric rotary machine according to the present invention, partially cut away with a plane including an axial line. In the preferred embodiment shown in  FIG. 1 , rotors  6  are arranged at both sides of a stator  5  in a direction of an axle O so as to oppose with each other via stator  5 . A gap portion  7  is provided between each of rotors  6  and stator  5 . A case  8  made of aluminum is installed on an outer periphery of stator  5 . Case  8  may be made of a metallic raw material having a high strength (rigidity), a light weight, and a high thermal conductivity, other than the aluminum raw material. Case  8  is a hollow cylindrical member with axle  0  as a center. Stator cores  9  are attached onto an inner wall  8   u  located at an inner peripheral surface of the hollow cylindrical member, viz., case  8 . A plurality of stator cores  9  are arranged in a peripheral direction of axle O and each of stator cores  9  is extended in the direction of axle O. 
         [0026]    Widths of both ends  9   t ,  9   t  of stator cores  9  in the direction of axle O are extended to secure areas of stator cores  9  abutting gap portion  7 . Coil windings  10  are wound around a middle portion of stator cores  9  located between both ends  9   t ,  9   t . Insulators  14  are attached onto both ends of coil windings  10  in the direction of axle O. Insulators  14  serve to secure the fixing of the ends of coil windings  10  in the direction of axle O onto the outer periphery of stator cores  9 . Stator cores  9  and coil windings  10  constitute an armature. 
         [0027]    A hollow cylindrical shaped inner peripheral ring  11  is arranged in an inner diameter direction of each of stator cores  9 . Inner peripheral ring  11  is made of aluminum and a shaft (not shown) extended along the direction of axle O and coupled with each rotor  6  is penetrated through a center hole  11   c  formed by an inner wall of inner peripheral ring  11 . Outer walls  11   s  of inner peripheral ring  11  are coupled with inner walls  8   u  of case  8  via thin plate members  12  extended in the radial direction of stator  5 . Theses thin plate members  12  are alternately arranged with respective stator cores  9  in the peripheral (circumferential) direction of axle O. Stator cores  9  on which coil windings  10  are wound are disposed between mutually adjacent case  8  and inner peripheral ring  11  in the radial direction and between mutually adjacent thin plate members  12 ,  12  in the peripheral direction. This disposition method is as follows: That is to say, a projection  23  such as a terminal projected from each of coil windings  10  is, at first, preliminarily fixed to each of outer walls  11   s  of inner peripheral ring  11  by means of a resin  21 . At the next stage, a resin  22  is used to enclose a whole surrounding of coil windings  10  and, thereafter, respective stator cores  9  on which coil windings  10  are wound are completely fixed onto inner walls  8   u  and outer walls  11   s.    
         [0028]    Case  8  is, as described above, formed of the hollow cylindrical shape. A thickness of case  8  in the radial direction of stator  5  is not wholly uniform. In other words, the thickness of case  8  in the radial direction of stator  5  is formed to become small (thin) so as to provide a recess from an inner wall direction of case  8  toward an outer diameter direction of case  8  at both ends of the axial direction of stator  5 . Thus, a space section  13  is provided at a portion (or position) of case  8  which is near to corresponding one of tips (or end)  9   t  of each stator core  9 . The radial directional thickness of each stator core  9  is formed largely (to become thick) for the inner wall of case  8  to become more inner diameter direction at the middle portion of the axial direction of case  8 , namely, at a portion at which the axial length and axial directional position of each stator core  9  are made coincident with case  8 . Thus, case  8  having a large thermal conductivity speedily discharges the heat generated by each stator core  9  and prevents an excessive heat of stator core  9 . 
         [0029]    Since each stator core tip (end)  9   t  is a magnetic pole of the armature, a magnetic flux density of a magnetic flux generated at each stator core  9  is largest at the proximity of each stator core tip  9   t . In addition, a permanent magnet (not shown) is installed on each rotor  6  and a magnetic pole of the permanent magnet is opposed against each stator core tip  9   t . Hence, gap portion  7  serves as an axial gap at a space (a space enclosed by a broken line in  FIG. 1 ) interposed between stator core tip  9   t  and the permanent magnet (not shown). 
         [0030]    A driving of the electric rotary machine is carried out by supplying appropriately an electric power to each coil winding  10 . The magnetic flux in the direction of axle O is developed on each stator core  9  during the power supply of each of coil windings  10  and a magnetic path (a magnetic circuit) is formed between both rotors  6 ,  6  via (axial) gap portion  7 . In this way, the magnetic path is directly formed between stator  5  and rotors  6  only via gap portions  7 . Thus, the torque is efficiently given to rotors  6  and rotors  6  are accordingly rotated. 
         [0031]    In this embodiment, each space sections  13  is provided at a position (or portion) of the case  8  near to each stator core tip  9   t  which is the magnetic pole of the stator side armature to interrupt the magnetic path between the stator and rotors. Hence, a large magnetic flux density developed at the proximity of each stator core tip  9   t  does not pass through case  8 . Hence, the bypassing of the magnetic flux of each stator core  9  through (axial) gap portion  7  can be eliminated. Thus, the generation of the eddy current at case  8  and a thermal loss thereat can be prevented. It becomes possible for the magnetic flux of each stator core  9  to be magnetically connected to rotors  6  via (axial) gap portion  7  without leakage of the magnetic fluxes of respective stator cores  9 . Consequently, the driving efficiency of the electric rotary machine can be improved. 
         [0032]    Next, the electric rotary machine in another preferred embodiment according to the present invention will be described below.  FIG. 2  shows a longitudinally cross sectioned view of the stator in the other preferred embodiment of the electric rotary machine with the plane including the axial line in cross section. The structure of this embodiment is basically common to a basic structure of the above-described preferred embodiment shown in  FIG. 1  but has a feature such that each space section is replaced with a bus-bar. That is to say, each space section in the embodiment is provided with bus-bar having the same size of each space section. Therefore, the same reference numerals as those shown in the above-described embodiment shown in  FIG. 1  are the like elements and their explanations will be omitted herein. For the different elements from the above-described embodiment, new reference numerals are attached and their detailed explanations will be made below. 
         [0033]    Bus-bar  15  is of an annular shape having approximately the same inner radius as case  8  and is equipped with a plurality of elements  16 . Each element  16  has an inner part of an electrically conductive portion and has its outer periphery of the electrically conductive portion enclosed with an insulating material. Bus-bar  15  serves to electrically connect each of coil windings  10  to an inverter (not shown) installed externally to the electric rotary machine shown in  FIG. 2  and serves to form a neutral point of three-phase alternating currents. In the embodiment shown in  FIG. 2 , bus-bar  15  in which three elements  16  through which three-phase alternating currents are individually caused to flow are aligned in the direction of axle O is attached onto each of both ends  9   t ,  9   t  in the direction of axle O of case  8 . In details, bus-bar  15  is divided in the direction of axle O and is provided with elements  16 . Then, bus-bar  15  is divided into small sizes in the direction of axle O and a size of each element  16  in the direction of axle O is made smaller than a size thereof in the radial direction which is a right angle to axle O. 
         [0034]    In this embodiment, bus-bar  15  is installed at the position near each stator core tip  9   t ,  9   t  which is the magnetic pole of the stator side armature. Since each element  16  constituting bus-bar  15  is enclosed with the insulating material, bus-bar  15  is divided into small (or narrow) sized elements in the direction of axle O when bus-bar  15  is viewed from a representative one of stator core tips  9   t ,  9   t . Hence, even if the magnetic flux enters each of small-sized (or narrow) elements  16 , the eddy current and its loss can be reduced. 
         [0035]    Next, the electric rotary machine of a still another preferred embodiment according to the present invention will be described below.  FIG. 3  shows a perspective view of the electric rotary machine with a part of case  8  cross sectioned. The basic structure of the still other preferred embodiment shown in  FIG. 3  is common to the embodiment shown in  FIG. 1  but a plurality of fins are installed in the axial direction within each space section  13 . In the still other preferred embodiment which will be described hereinbelow, the same elements as those in the embodiment shown in  FIG. 1  are not shown. 
         [0036]    A plurality of block-shaped fins  17  are installed at each end (tip) in the axle direction of case  8  of the hollow cylindrical shape along the peripheral direction of case  8 , as shown in  FIG. 3 . Therefore, a plurality of space sections  13  are formed between mutually abutting fins  17 . In other words, rectangular cross sectioned recesses  13  are formed in the peripheral (circumferential) direction of case  8  at each axial end portion of case  8  of the hollow cylindrical shape. 
         [0037]    Fins  17  and other space sections  13  are disposed on positions near stator core tips  9   t ,  9   t  which are the magnetic poles of the stator side armature. When these fins  17  located at an outer diameter side of inner wall  8   u  are viewed from stator core tips  9   t ,  9   t  located at the inner diameter side of inner wall  8   u , fins  17  are divided into small divisions in the peripheral direction of case  8 . Hence, even if the magnetic flux from each stator core tip  9   t  enters each small divided fin  17 , the eddy current and its loss can be reduced. In addition, since each fin  17  is of the block shape, a rigidity of each end portion of case  8  can be secured. 
         [0038]    In the embodiment shown in  FIG. 3 , another space section  18  is provided within an inner side of case  8  and a refrigerant is caused to flow through this space section  18 . Thus, a temperature rise in the electric rotary machine can be prevented. Case  8  is formed of a metal such as aluminum having the high thermal conductivity. Hence, heat at each stator core  9  and each coil winding  10  of the electric rotary machine speedily passes inner wall  8   u  and is exhausted at this space section  18 . 
         [0039]    Next, a further another preferred embodiment of the electric rotary machine will be described below.  FIG. 4  shows a perspective view of the electric rotary machine whose part of case  8  is cross sectioned in the further other preferred embodiment of the electric rotary machine. A basic structure of the embodiment shown in  FIG. 4  is common to the embodiment shown in  FIG. 1  on all other members than the case and, therefore, the drawings thereof will be omitted herein. However, different components will be described with new reference numerals attached. 
         [0040]    As shown in  FIG. 4 , space section  18  is installed in an inner part of case  8  of hollow cylindrical shape as in the same case of the still other embodiment shown in  FIG. 3 . Space section  18  is arranged with axial ends thereof extended as large as possible in the axial direction and extended toward the inner diameter side (as large as possible). A plurality of fins  19  of block shapes are extended at two of four corners of space section  18  located at the inner diameter side at the axial end portions of case  8 .  FIG. 5  shows a cross sectioned view cut away along a plane A-A denoted by a dot-dot-and-dash line with a part of case  8  in cross section and  FIG. 6  shows a cross sectioned view cut away along a plane B-B denoted by a dot-dot-and-dash line with a part of case  8  thereof in cross section. As compared with  FIGS. 5 and 6 , it will be appreciated that the plurality of fins  19  are disposed in the peripheral direction of case  8  as space section  18  is present between these abutting fins  19 . A refrigerant is filled within space section  18  and this refrigerant is circulated between space section  18  and a radiator to provide space section  18  with a passage of the refrigerant. 
         [0041]    In this embodiment, space section  18  is formed within the inner part of case  8  supporting each stator core  9  and extended toward a position near to each stator core tip  9   t . Space section  18  provides a passage through which the refrigerant is caused to flow in an inner part of case  8  supporting each stator core  9 . Hence, even if the magnetic flux from each stator core tip  9   t ,  9   t  enters case  8 , the eddy current and its loss can be reduced. 
         [0042]    In this embodiment, when one of fins  19  shown in  FIGS. 4 and 6  is viewed from stator core tip  9   t , each of fins  19  is divided as a narrower unit in the peripheral direction of case  8 . Hence, even if the magnetic flux from stator core tip  9   t  enters each small fin  19 , the eddy current and its loss can be reduced. In addition, since each fin  19  is of the block shape, the rigidity of each end of case  8  can be secured. 
         [0043]    In order to confirm the effect of the further other preferred embodiment shown in  FIGS. 4 through 6 , the applicants (inventors) of the present application uses a model of the same as the analytical model ( FIG. 9 ) explained in the above-described SUMMARY OF THE INVENTION. 
         [0044]      FIG. 7  shows a perspective view of case  8  equivalent to outer peripheral ring G as inner peripheral ring  11  equivalent to inner peripheral ring F shown in  FIG. 9  as viewed from an arrow-marked direction in  FIG. 9 . When the electric rotary machine in the further other preferred embodiment shown in  FIGS. 4 through 6  is in the acceleration driving as the electric rotary machine of the axial gap type in the comparative example with the same predetermined electric power, magnetic flux density distribution of the leakage magnetic flux passing through inner peripheral ring F and outer peripheral ring G not the rotor nor the stator is divided into a plurality of zones. In the inner part of case  8  shown in  FIGS. 7 and 8 , space section  18  is disposed in the inner part of case  8  as shown in  FIGS. 4 through 6 . 
         [0045]    In  FIG. 7 , zone  4 A indicates a large magnetic flux density, and the magnetic flux densities become smaller in the order of zone  3 A, zone  2 A, and zone  1 A. While comparing with outer peripheral ring G of the comparative example of the electric rotary machine shown in  FIG. 10  having no space section  18 , case  8  shown in  FIG. 7  indicating the effect of the embodiment shown in  FIGS. 4 through 6  is analyzed. In this case, the density distribution of the leakage magnetic flux can remarkably be reduced according to the case in the embodiment shown in  FIGS. 4 through 6  according to the present invention. 
         [0046]      FIG. 8  shows the eddy current density distribution caused by the leakage magnetic flux described above in the zone division form. In  FIG. 8 , zone  4 A′ is the large eddy current density and the eddy current densities become smaller in the order of zone  3 A′, zone  2 A′, and zone  1 A′. 
         [0047]    When case  8  shown in  FIG. 8  is viewed indicating the effect of the embodiment shown in  FIGS. 4 through 6 , while comparing with outer peripheral ring G of the comparative example shown in  FIG. 11  having no space section  18 , the density distribution of the eddy current can remarkably be reduced according to case  8  in the embodiment according to the present invention. 
         [0048]    According to each embodiment described above, the position of case  8  made of a metal and supporting stator cores  9  of the stator which faces against gap portion  7  near magnetic pole  9   t  of stator side armature is provided with space section  13  which interrupts the magnetic path. Hence, the problem such that the large magnetic flux passes the case can be eliminated, a thermal loss due to the eddy current is largely suppressed, and an undesired temperature rise of the electric rotary machine can be suppressed. In addition, the leakage of the magnetic flux from the magnetic path formed via gap portion  7  between stator core tip  9   t  and rotor  6  can be eliminated. The magnetic path is formed so as to connect magnetic pole  9   t  of the stator side armature installed on stator  5  and the magnetic pole or a salient pole of the permanent magnet installed on rotor  6  at a shortest distance. The improvement in the driving efficiency and an augment effect of the torque can be expected. When the large torque driving at which the magnetic flux density of the magnetic path becomes large is carried out, the effect of the heat generation suppression and that of the improvement in the driving efficiency can be enjoyed. 
         [0049]    In addition to space sections  13  in the embodiment shown in  FIG. 1 , specifically, if space sections  13  are replaced with (or provided with) bus-bar  15  enclosed with the insulating material for connecting each coil winding  10  to the inverter (not shown) of the electric rotary machine, the same effect as the embodiment shown in  FIG. 1  can be achieved. 
         [0050]    In the embodiment shown in  FIG. 2 , bus-bar  15  as viewed from magnetic pole  9   t  of stator  5  is divided narrowly into the plurality of elements  16 , each enclosed with the insulating material. Thus, even if the magnetic flux from each stator core tip  9   t  enters each element  16  whose magnetic flux is narrowly small, the eddy current and its loss can be reduced. 
         [0051]    In addition, in the embodiment shown in  FIG. 3 , a plurality of fins  17  are installed within space sections  13 . Hence, the rigidity (or strength) of each end portion of case  8  can be secured. 
         [0052]    In the embodiment shown in  FIG. 3 , as viewed from magnetic pole  9   t  of stator  5 , fins  17  and space sections  13  positioned between mutually abutting fins  17  are alternately aligned. Hence, fins  17  are divided narrowly into small ones. Even if the magnetic flux from each magnetic pole tip  9   t  of stator  5  enters each small fin  17 , the eddy current and its loss can be reduced. Furthermore, the provision of fins  17  can secure the rigidity of each end portion of case  8 . It should be noted that, in each of the embodiments shown in  FIGS. 1 through 3 , space section  18  may be provided at the inner part of case  8  and the refrigerant may be caused to flow through space section  18 . 
         [0053]    In addition, space section  18  is formed as a passage through which the refrigerant is caused to flow in the inside (inner part) of case  8  in the embodiment shown in  FIG. 4 . This passage is utilized as space section  18  interrupting the magnetic path. Hence, the same effects as those in each of the embodiments shown in  FIGS. 1 through 3  can be exhibited. 
         [0054]    In addition, in each embodiment shown in  FIGS. 1 through 4 , metallic member supporting stator  5  is a case  8  forming a crust of the electric rotary machine. Thus, the heat can be exhausted to an external portion of the outside of case  8  speedily from case  8  from each stator core  9  and each of coil windings  10  which are heat sources of stator  5 , the strength (rigidity) of stator  5  can be secured, the rise in temperature exceeding an appropriate temperature range can effectively be prevented. 
         [0055]    In addition, in each embodiment shown in  FIGS. 1 through 4 , stator  5  and rotors  6  are opposed in the direction of axle O to form the axial gap electric rotary machine. Case  8  is formed of the hollow cylindrical shape and supports stator  5  with inner wall  8   u . Hence, the effect of the present invention can enjoy the axial gap electric rotary machine. 
         [0056]    Specifically, in the embodiment of the axial gap electric rotary machine shown in  FIG. 2 , bus-bar  15  is arranged at substantially the same position as the position of axle O of each magnetic pole  9   t  of stator  5  and this bus-bar  15  is divided into the direction of axle O so that three elements  16  are formed, the size of the direction of axle O of these elements  16  being made smaller than the size of the radial direction thereof. Hence, even if the magnetic flux from each stator core tip  9   t  enters each small element  16 , the eddy current and its loss can be reduced. 
         [0057]    This application is based on a prior Japanese Patent Application No. 2006-131400. The entire contents of a Japanese Patent Application No. 2006-131400 with a filing date of May 10, 2006 are hereby incorporated by reference. Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art in light of the above teachings. For example, the present invention is not only applicable to the axial gap electric rotary machine but also applicable to a radial gap electric rotary machine. The scope of the invention is defined with reference to the following claims.