Abstract:
A dynamo-electric machine reduces the increase in temperature of a stator close to a cooling liquid outlet and a stator end portion, and that has excellent cooling performance. The dynamo-electric machine is provided with: a stator, a rotor that is held on the inner-diameter-side of the stator across a predetermined gap so as to be capable of rotating; and a housing that is located on the outer-diameter-side of the stator and holds the stator and the rotor. The housing is provided with a cooling liquid channel through which a cooling liquid flows, the radial height of the cooling liquid channel within the housing differing depending on the axial position of the rotor.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a structure of a rotating electric machine. 
       BACKGROUND ART 
       [0002]    Rotating electric machines include a rotor which rotates about a rotating shaft, a stator disposed opposite to a circumferential surface of the rotor and with a stator coil winded around a stator core, and a housing which fixes the stator and rotatably holds the rotor. 
         [0003]    When a rotating electric machine is operated as an electric motor, an AC current is fed to the stator coil and a rotating magnetic field is generated, thereby giving turning force to the rotor to obtain mechanical output. Meanwhile, when a rotating electric machine is operated as a generator, turning force is externally given to the rotor to allow the rotor to rotate, thereby obtaining electric output generated at the stator coil. 
         [0004]    When a rotating electric machine is operated as an electric motor or a generator in this manner to obtain mechanical output or electric output, the stator coil and the stator core generate heat due to loss of the rotating electric machine. An insulating material used for the rotating electric machine has an upper limit temperature that allows for maintaining insulating performance. Therefore, in order to maintain the temperature of the insulating material of the rotating electric machine to be less than or equal to the upper limit temperature, it is required to cool the rotating electric machine by some method when the rotating electric machine is operated. 
         [0005]    Classifying cooling methods of the rotating electric machine by a medium used for cooling, the methods are divided into gas cooling methods using gas such as the air or hydrogen as a cooling medium and liquid cooling methods using liquid such as cooling water or cooling oil as a cooling medium. 
         [0006]    Of the above, the liquid cooling methods can be classified into indirect cooling methods to indirectly cool a stator core and a stator coil by cooling a housing by circulating cooling liquid in a passage included in the housing and direct cooling methods to cool a stator core or a stator coil that is a portion generating heat by bringing cooling liquid, such as cooling oil having electric insulation property, into direct contact with the stator core or the stator coil. 
         [0007]    It is known that in the indirect cooling methods a passage structure of the cooling liquid significantly influence cooling performance. For example, PTL 1 discloses a passage structure of a housing that allows for suppressing deterioration of cooling efficiency due to stagnation of cooling water. 
       CITATION LIST 
     Patent Literature 
       [0008]    PTL 1: JP 2009-247085 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0009]    In rotating electric machines of the indirect cooling methods, however, a temperature rise at an end portion of a stator is higher than a temperature rise at the central portion of the stator due to the following reasons. 
         [0010]    A housing and a stator are in contact with each other at apart of a stator core where electrical steel plates are laminated, thereby radiating heat generated at the stator into cooling liquid in the housing. Generation of heat at the stator is attributable to iron loss generated at the stator core and copper loss generated at the stator coil. Of the above, the copper loss is equivalent to Joule heat generated by a current flowing in the stator coil. This is generated at a stator coil thick portion inserted in the laminated portion of the stator core and at a stator coil end portion protruding from an end portion of the stator core in the axial direction for winding around the stator core. The copper loss generated at the stator coil thick portion is transferred to the stator core in contact therewith and the heat is radiated to the cooling liquid via the housing. However, the copper loss generated at the stator coil end portion that is not in contact with the stator core is transferred to the stator coil thick portion and then transferred to the stator core and the heat is radiated to the cooling liquid via the housing. Therefore, the stator coil end portion has a higher temperature as compared to that of the stator coil thick portion. 
         [0011]    Furthermore, the cooling liquid absorbs the heat radiated from the stator while flowing in the passage in the housing and thus a cooling liquid temperature rises while the cooling liquid flows in the passage in the housing. Therefore, the passage near a cooling liquid inlet lets the cooling liquid of a low temperature flow and thus has high heat radiation performance while the passage near a cooling liquid outlet lets the cooling liquid of a high temperature flow and thus has low heat radiation performance. Thus, there is a problem that a stator temperature near the cooling liquid outlet becomes higher than a stator temperature near the cooling liquid inlet. 
         [0012]    An object of the present invention is to provide a rotating electric machine having excellent cooling performance where a temperature rise at a stator end portion and a stator near a cooling liquid outlet is mitigated. 
       Solution to Problem 
       [0013]    In order to solve the above problem, configurations described in claims are employed for example. 
         [0014]    The present application includes a plurality of means to solve the above problem. One example of the means includes a stator; a rotor rotatably held on an inner diameter side of the stator via a predetermined gap; and a housing positioned on an outer diameter side of the stator, the housing retaining the stator and the rotor. The housing includes a cooling liquid passage which distributes cooling liquid. The height in a radial direction of the cooling liquid passage of the housing is different depending on a position in an axial direction of the rotor. 
       Advantageous Effects of Invention 
       [0015]    The present invention allows for providing a rotating electric machine having excellent cooling performance where a temperature rise at a stator end portion and a stator near a cooling liquid outlet is mitigated. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is a cross-sectional view of a rotating electric machine according to a first embodiment. 
           [0017]      FIG. 2  is a perspective view of a housing of the rotating electric machine according to the first embodiment. 
           [0018]      FIG. 3  is a cross-sectional view of the rotating electric machine according to the first embodiment. 
           [0019]      FIG. 4  is a cross-sectional view of a rotating electric machine according to a second embodiment. 
           [0020]      FIG. 5  is a cross-sectional view of a rotating electric machine according to a third embodiment. 
           [0021]      FIG. 6  is an exploded cross-sectional view of the rotating electric machine according to the third embodiment. 
           [0022]      FIG. 7  is a cross-sectional view of the rotating electric machine according to the third embodiment. 
           [0023]      FIG. 8  is a cross-sectional view of the rotating electric machine according to the third embodiment. 
           [0024]      FIG. 9  is a cross-sectional view of the rotating electric machine according to the third embodiment. 
           [0025]      FIG. 10  is a cross-sectional view of a rotating electric machine according to a fourth embodiment. 
           [0026]      FIG. 11  is a cross-sectional view of a rotating electric machine according to a fifth embodiment. 
           [0027]      FIG. 12  is a cross-sectional view of the rotating electric machine according to the fifth embodiment. 
           [0028]      FIG. 13  is a cross-sectional view of a rotating electric machine according to a sixth embodiment. 
           [0029]      FIG. 14  is a perspective view of a housing of the rotating electric machine according to the sixth embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0030]    Embodiments will be described below with reference to the drawings. 
         [0031]    Incidentally, in the descriptions below, an “axial direction” refers to a direction along a rotating shaft of a rotor of a rotating electric machine. A “circumferential direction” refers to a direction along a rotating direction of the rotor of the rotating electric machine. A “radial direction” refers to a radius vector direction (radial direction) when the rotating shaft of the rotor of the rotating electric machine is regarded as the center. An “inner periphery side” refers to an inner side (inner diameter side) of the radial direction while an “outer periphery side” refers to the opposite, that is, an outer side (outer diameter side) of the radial direction. 
       First Embodiment 
       [0032]    A rotating electric machine of a first embodiment of the present invention will be described with  FIGS. 1 to 3 . 
         [0033]      FIG. 1  illustrates a cross-sectional view of a rotating electric machine  100  of the first embodiment of the present invention. 
         [0034]    The rotating electric machine  100  of the first embodiment of the present invention includes a housing  110 , a stator  300  fixed to the housing, a rotor  400  rotatably supported by a bearing  200  fixed to the housing  110 , and an end bracket  500  to be attached to an end portion, in the axial direction, of the housing  110 . 
         [0035]    The stator  300  includes a stator core  310  formed by lamination of thin electrical steel plates, a stator coil  320 , and an insulating material (not illustrated) to electrically insulate the stator core  310  and the stator coil  320 . 
         [0036]    The housing  110  includes a passage  113  to let cooling liquid flow to cool the rotating electric machine. 
         [0037]      FIG. 2  illustrates the housing  110  of the rotating electric machine of the first embodiment of the present invention. In  FIG. 2 , an object illustrated by broken lines is a cooling liquid passage inside the housing  110 . A solid line arrow in  FIG. 2  illustrates a direction of a flow of cooling liquid. 
         [0038]    In the first embodiment of the present invention, the height of the cooling liquid passage  113  (thickness in the radial direction) is different depending on a position in the axial direction where the cooling liquid passage  113  in the housing  110  is included in the housing  110  by a plurality of rounds in the circumferential direction as illustrated in  FIG. 2 . 
         [0039]    In  FIG. 1 , the height of passages  113   a  and  113   b  at the both ends in the axial direction is lower than the height of the central portion  113   b  in the axial direction. This allows the passages  113   a  and  113   c  to have a cross-sectional area smaller than a cross-sectional area of the passage  113   b  and thus have a larger flow rate when cooling liquid flows therein. This results in higher cooling performance of the passages  113   a  and  113   c  than cooling performance of the passage  113   b , thereby allowing for mitigating a temperature rise at the end portions of the stator  300  in the axial direction. 
         [0040]    Alternatively, as illustrated in  FIG. 3 , the height of a cooling liquid passage  113   b  in the central portion in the axial direction may be lower than those of cooling liquid passages  113   a  and  113   c  at the end portions in the axial direction, thereby enhancing cooling performance in the central portion in the axial direction. This is effective when, as illustrated in  FIG. 3 , cooling oil  600  having insulation property is sealed inside a rotating electric machine and direct cooling by the cooling oil  600  and indirect cooling by cooling liquid flowing in a cooling liquid passage  113  of a housing  110  are combined. In this case, end portions of a stator coil  320  in the axial direction are cooled by the cooling oil and thus a temperature at the central portion in the axial direction may be higher than a temperature at the end portions in the axial direction. In this case, as illustrated in  FIG. 3 , by lowering the height of the cooling liquid passage  113   b  in the central portion in the axial direction than those of the cooling liquid passages  113   a  and  113   c  at the end portions in the axial direction and thereby enhancing cooling performance in the central portion in the axial direction, a temperature rise in the central portion in the axial direction can be mitigated. 
         [0041]    Incidentally, the cooling liquid passage  113  is formed by three rounds in the circumferential direction in  FIGS. 1 to 3 ; however, this does not limit the number of rounds. The characteristic of the present invention is to vary the height of cooling liquid passages of a plurality of rounds depending on a position thereof. 
       Second Embodiment 
       [0042]    A rotating electric machine of a second embodiment of the present invention will be described with  FIG. 4 .  FIG. 4  is a cross-sectional view of the rotating electric machine of the second embodiment of the present invention. 
         [0043]    In the rotating electric machine of the second embodiment of the present invention, the height in the radial direction of a cooling liquid passage  113  included in the housing  110  varies depending on a position in the axial direction. A cooling liquid inlet  115   a  is provided to a cooling liquid passage  113   a  having a high height in the radial direction while a cooling liquid outlet  115   b  is provided to a cooling liquid passage  113   c  having a low height in the radial direction. 
         [0044]    The cooling liquid passage  113   a  provided with the cooling liquid inlet  115   a  has a high height in the radial direction and a large cross-sectional area and thus has a small heat transfer coefficient but can obtain high cooling performance since the temperature of cooling liquid is low thereat. 
         [0045]    Meanwhile, in the cooling liquid passage  113   c  provided with the cooling liquid outlet  115   b , since the cooling liquid absorbs the heat generated by the rotating electric machine while flowing in the cooling liquid passage, the cooling liquid temperature becomes higher than that of the cooling liquid flowing in the cooling liquid passage  113 . However, since the height in the radial direction is low and the cross-sectional area of the passage is small, a high heat transfer coefficient can be obtained. As a result of this, a temperature rise of the rotating electric machine near the cooling liquid outlet attributable to a temperature rise of the cooling liquid can be mitigated. 
       Third Embodiment 
       [0046]    A rotating electric machine of a third embodiment of the present invention will be described with  FIGS. 5 and 9 .  FIG. 5  is a cross-sectional view of the rotating electric machine of the third embodiment of the present invention.  FIG. 6  is an exploded cross-sectional view of the rotating electric machine of the third embodiment of the present invention. 
         [0047]    In the rotating electric machine of the third embodiment of the present invention, a housing  110  has a double cylinder structure of an inner cylinder  111  and an outer cylinder  112 . An outer diameter surface  111   a  of the inner cylinder  111  and an inner diameter surface  112   a  of the outer cylinder  112  are inclined in the axial direction and the outer diameter surface  111   a  of the inner cylinder  111  includes a groove that forms a cooling liquid passage  113 . 
         [0048]    Since the outer diameter surface  111   a  of the inner cylinder  111  is inclined in the axial direction, a cross-sectional area of the cooling liquid passage  113  decreases gradually from the left to the right in  FIG. 5 . Due to this, by providing a cooling liquid inlet  115   a  to a passage  113   a  having the largest cross-sectional area and providing a cooling liquid outlet  115   b  to a cooling liquid passage  113   c  having the smallest cross-sectional area, influence of a temperature rise of the cooling liquid can be removed like in the rotating electric machine of the second embodiment of the present invention. 
         [0049]    Moreover, an outer diameter of the inner cylinder  111 , at a position in contact with the outer cylinder  112  when the inner cylinder  111  and the outer cylinder  112  are assembled, is formed to be smaller than an inner diameter of the outer cylinder  112  and thereby a fastening margin is set such that the inner cylinder  111  is fastened by the outer cylinder  112  in the inner diameter direction. This allows for fastening the stator  300  and the inner cylinder  111  to each other. 
         [0050]    In  FIGS. 5 and 6 , seal portions  114  of the inner cylinder  111  and the outer cylinder  112  are provided on end surfaces of the inner cylinder  111  in the axial direction; however, this does not specifically specify a position of the seal portion. As illustrated in  FIGS. 7 to 9 , two seal portions  114  may be provided on an outer diameter surface of the inner cylinder  111  or one seal portion may be provided on an outer diameter surface of an inner cylinder  111  while the other seal portion  114  is provided on an end surface of the inner cylinder  111  in the axial direction. 
       Fourth Embodiment 
       [0051]    A fourth embodiment of the present invention will be described with  FIG. 10 . 
         [0052]      FIG. 10  is a cross-sectional view of a rotating electric machine illustrating the fourth embodiment of the present invention. 
         [0053]    The fourth embodiment of the present invention has a double cylinder structure where a housing  110  is formed by an inner cylinder  111  and an outer cylinder  112  like in the third embodiment. However, only a part where the inner cylinder  111  and the outer cylinder  112  are in contact with each other is inclined in the axial direction while the inner diameter of a part of the outer cylinder  112  where a cooling liquid passage  113  is formed is constant. 
       Fifth Embodiment 
       [0054]    A fifth embodiment of the present invention will be described with  FIGS. 11 and 12 . 
         [0055]      FIGS. 11 and 12  are cross-sectional views of a rotating electric machine illustrating the fifth embodiment of the present invention. 
         [0056]    The fifth embodiment of the present invention has a double cylinder structure where a housing  110  is formed by an inner cylinder  111  and an outer cylinder  112  like in the third and the fourth embodiments. However, a cooling liquid passage is included in both of an outer diameter side of the inner cylinder  111  and an inner diameter side of the outer cylinder  112  or only on an inner diameter side of the outer cylinder  112 . 
         [0057]    This allows for changing cooling performance by changing only the outer cylinder  112  without changing the stator  300 , the rotor  200 , or the inner cylinder  111  when cooling conditions (for example a cooling liquid temperature or the like) of the rotating electric machine are changed. 
       Sixth Embodiment 
       [0058]    A sixth embodiment of the present invention will be described with  FIGS. 13 and 14 . 
         [0059]      FIG. 13  is a cross-sectional view illustrating a rotating electric machine of the sixth embodiment of the present invention.  FIG. 14  illustrates a housing  110  of the rotating electric machine of the sixth embodiment of the present invention. 
         [0060]    In the sixth embodiment of the present invention, a cooling liquid passage  113  of the housing  110  is included in the axial direction where the height of the cooling liquid passage  113  at end portions in the axial direction is smaller than the height of the cooling liquid passage  113  at the central portion in the axial direction. 
         [0061]    This allows for enhancing cooling performance at the end portions in the axial direction like in the first embodiment of the present invention even when the cooling liquid passage  113  in the housing  111  is a flow rate in the axial direction. 
         [0062]    Incidentally, the present invention is not limited to the aforementioned embodiments and may include various variations. For example, the aforementioned embodiments are described in detail in order to facilitate understanding of the present invention and thus the present invention is not necessarily limited to the one including all of the configurations having been described. A part of a configuration of one of the embodiments may be replaced with a configuration of another embodiment. Also, a configuration of one of the embodiments may be added with a configuration of another embodiment. Moreover, a part of a configuration of each of the embodiments may be added with, deleted of, or replaced with another configuration. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           100  rotating electric machine 
           110  housing 
           111  housing inner cylinder 
           112  housing outer cylinder 
           113  cooling liquid passage 
           113   a  cooling liquid passage 
           113   b  cooling liquid passage 
           113   c  cooling liquid passage 
           114  seal portion 
           115   a  cooling liquid inlet 
           115   b  cooling liquid outlet 
           200  bearing 
           300  stator 
           310  stator core 
           320  stator coil 
           400  rotor 
           500  end bracket 
           600  cooling oil