Patent Publication Number: US-2016233744-A1

Title: Rotary electric machine

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2015-022903 filed on Feb. 9, 2015 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rotary electric machine, and particularly to a cooling structure of a rotor. 
     2. Description of Related Art 
     In a rotary electric machine of the following Japanese Patent Application Publication No. 2014-176235, a rotor is cooled by supplying a liquid coolant from a coolant passage formed inside a rotor shaft to each cooling flow passage formed inside a rotor core. 
     In JP 2014-176235 A, the liquid coolant is directly supplied from the coolant passage inside the rotor shaft to each cooling flow passage inside the rotor core; therefore, amount of the liquid coolant supplied to each cooling flow passage inside the rotor core varies due to variation in pressure or the like of the liquid coolant in the coolant passage inside the rotor shaft. 
     SUMMARY OF THE INVENTION 
     The present invention provides a rotary electric machine that suppresses variation in cooling performance of a rotor using a liquid coolant. 
     A rotary electric machine related to one aspect of the present invention includes a rotor and a rotor shaft. The rotor has a cooling flow passage and the rotor shaft is fixed to an inner peripheral surface of the rotor. The rotor shaft has a hollow part to which the liquid coolant is supplied, a coolant flow inlet that provides communication between the hollow part and the cooling flow passage, and a coolant supply shaft extending through the hollow part. The coolant supply shaft has a coolant discharge port that discharges the liquid coolant to the hollow part. A position in a rotor axial direction of the coolant flow inlet deviates from a position in the rotor axial direction of the coolant discharge port. 
     According to the present invention, each coolant flow inlet formed in the rotor shaft deviates from each coolant discharge port formed in the coolant supply shaft in either one of the rotor axial direction and the rotor circumferential direction, thereby suppressing direct influence of the flow of the liquid coolant discharged from the coolant discharge ports onto the flow of the coolant flow inlets. Accordingly, it is possible to suppress variation in amount of the liquid coolant supplied through the coolant flow inlets to the cooling flow passages of the rotor, thus suppressing variation in cooling performance of the rotor using the liquid coolant. 
     A rotary electric machine related to a second aspect of the present invention includes a rotor and a rotor shaft. The rotor has a cooling flow passage through which a liquid coolant flows and the rotor shaft is fixed to an inner peripheral surface of the rotor. The rotor shaft has a hollow part to which the liquid coolant is supplied, a coolant flow inlet that provides communication between the hollow part and the cooling flow passage, and a coolant supply shaft extending through the hollow part. The coolant supply shaft has a coolant discharge port that discharges the liquid coolant to the hollow part. A position in a rotor circumferential direction of the coolant flow inlet deviates from a position in the rotor circumferential direction of the coolant discharge port. 
     In the second aspect of the present invention, a position in the rotor axial direction of the coolant flow inlet may deviate from a position in the rotor axial direction of the coolant discharge port. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
         FIG. 1  is a longitudinal sectional view showing a configuration example of a rotary electric machine according to an embodiment of the present invention; 
         FIG. 2  is a view illustrating a flow of a liquid coolant in the rotary electric machine according to the embodiment of the present invention; and 
         FIG. 3  is a cross sectional view showing another configuration example of the rotor shaft and the coolant supply shaft in the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT 
     Hereinafter, a mode for carrying out the present invention (hereinafter, referred to as an embodiment) will be described with reference to drawings. 
       FIG. 1  is a longitudinal sectional view showing a schematic configuration of a rotatory electric machine according to the embodiment of the present invention. In the rotatory electric machine, a stator  10  is disposed circumferentially outward of a rotor  20 , and the rotor  20  and the stator  10  are so arranged as to oppose each other with a distance (magnetic gap) in a radial direction therebetween. The stator  10  includes a stator core  11  and a coil  12  disposed to the stator core  11 . The rotor  20  includes a rotor core  21  and plural permanent magnets  22  arranged in a rotor circumferential direction with intervals (e.g., equal intervals) therebetween in the rotor core  21 . Each permanent magnet  22  extends in a rotor axial direction (direction along a rotational axis of the rotor  20 ). An inner peripheral surface of the rotor core  21  defines a shaft fitting hole  30  in a manner as to extend in the rotor axial direction. A rotor shaft  16  is fitted into the shaft fitting hole  30  for example by press-fitting or the like, so as to fit the rotor shaft  16  extending in the rotor axial direction to the inner peripheral surface of the rotor  20 . The rotor shaft  16  is rotatably supported by a housing  60  through bearings  61 A,  61 B so that the rotor  20  is rotatable relative to the stator  10  as well as the rotor shaft  16 . 
     In order to cool the rotor  20 , cooling flow passages through which a liquid coolant, such as a cooling oil, passes are formed inside the rotor core  21 , for example. Inside the rotor shaft  16 , there is formed a hollow part  17  to which a liquid coolant is supplied is formed in a manner as to extend in the rotor axial direction. The rotor shaft  16  is provided with plural coolant flow inlets  18  that provide communication between the hollow part  17  and the cooling flow passages of the rotor core  21 . The plural coolant flow inlets  18  are arranged in the rotor circumferential direction with intervals (e.g., equal intervals) therebetween, and each coolant flow inlet  18  extends in the rotor radial direction. 
     The cooling flow passages of the rotor core  21  include plural first and second cooling flow passages  41 ,  42 . The plural first cooling flow passages  41  are arranged in the rotor circumferential direction with intervals (e.g., equal intervals) therebetween. Each first cooling flow passage  41  is disposed circumferentially inward of the permanent magnets  22  in a manner as to extend in the rotor axial direction. Both ends in the rotor axial direction of each first cooling flow passage  41  open toward an outside of the rotor. The plural (the same number of the first cooling flow passages  41  and the coolant flow inlets  18 ) second cooling flow passages  42  are arranged in the rotor circumferential direction with intervals (e.g., equal intervals) therebetween. Each second cooling flow passage  42  provides communication between each coolant flow inlet  18  and each first cooling flow passage  41 , and in an example of  FIG. 1 , each second cooling flow passage  42  extends from an inner end in the rotor radial direction thereof that communicates with each coolant flow inlet  18  to an outer end in the rotor radial direction thereof that communicates with each first cooling flow passage  41  in a manner as to branch stepwise into two. However, each second cooling flow passage  42  is unnecessarily formed to branch into two, and to extend stepwise. In the example of  FIG. 1 , each coolant flow inlet  18  and each second cooling flow passage  42  are connected to each other at a center position in the rotor axial direction thereof, but the connecting position in the rotor axial direction between each coolant flow inlet  18  and each second cooling flow passage  42  is unnecessary to be the center position. 
     A coolant supply shaft  50  extends in the rotor axial direction through the hollow part  17  inside the rotor shaft  16 . In other words, an inner peripheral surface of the rotor shaft  16  and an outer peripheral surface of the coolant supply shaft  50  define a gap therebetween. The coolant supply shaft  50  is rotationally supported by a housing  60  through not-shown bearings. Furthermore, the coolant supply shaft  50  is supported by the rotor shaft  16  via seal members  62 A,  62 B. The seal members  62 A,  62 B are arranged with a distance in the rotor axial direction therebetween, and the hollow part  17  is located between the seal members  62 A,  62 B so that leakage of the liquid coolant from the hollow part  17  is prevented by the seal members  62 A,  62 B. The coolant supply shaft  50  is integrally rotated with the rotor  20  and the rotor shaft  16  at the same rotational speed. 
     Inside the coolant supply shaft  50 , a coolant passage  51  through which the liquid coolant discharged from a not-shown pump flows is so formed as to extend in the rotor axial direction. In the coolant supply shaft  50 , plural coolant discharge ports  52  that provide communication between the coolant passage  51  and the hollow part  17  of the rotor shaft  16  are also formed. The plural coolant discharge ports  52  are arranged in the rotor circumferential direction with intervals (e.g., equal intervals) therebetween. 
     In the present embodiment, in order to prevent each coolant flow inlet  18  of the rotor shaft  16  from opposing each coolant discharge port  52  of the coolant supply shaft  50  in the rotor radial direction, the coolant flow inlets  18  are arranged such that a rotor axial position of each coolant flow inlet  18  is different from a rotor axial position of each coolant discharge port  52  so as to locate each coolant flow inlet  18  at a position deviating in the rotor axial direction from each coolant discharge port  52 . In the example of  FIG. 1 , each coolant discharge port  52  is illustrated at only one rotor axial position, and each coolant flow inlet  18  is illustrated at only one rotor axial position, but there may be formed the coolant discharge ports  52  at plural rotor axial positions, and there may be formed the coolant flow inlets  18  at plural rotor axial positions as far as a condition that each coolant flow inlet  18  deviates from each coolant discharge port  52  in the rotor axial direction so that each coolant flow inlet  18  does not oppose each coolant discharge port  52  in the rotor radial direction is satisfied. 
     The liquid coolant supplied from the not-shown pump flows through the coolant passage  51  inside the coolant supply shaft  50 , and is discharged from each coolant discharge port  52  into the hollow part  17  inside the rotor shaft  16  as indicated by an arrow A of  FIG. 2 , thereby temporarily storing the liquid coolant in the hollow part  17 . The liquid coolant stored in the hollow part  17  inside the rotor shaft  16  flows into each coolant flow inlet  18  by a centrifugal force at the time of rotation of the rotor. The liquid coolant having flown into each coolant flow inlet  18  is supplied to each second cooling flow passage  42  as indicated by an arrow B of  FIG. 2 , and is then supplied to each first cooling flow passage  41 . The liquid coolant flows through the second cooling flow passages  42  and the first cooling flow passages  41 , thereby cooling the rotor  20  (the rotor core  21  and the permanent magnets  22 ). The liquid coolant flowing through the first cooling flow passages  41  is discharged from the both ends in the rotor axial direction of each first cooling flow passage  41  to the outside of the rotor as indicated by arrows C of  FIG. 2 . 
     Herein, supposing a case in which each coolant flow inlet  18  of the rotor shaft  16  opposes each coolant discharge port  52  of the coolant supply shaft  50  in the rotor radial direction, the liquid coolant discharged from each coolant discharge port  52  is directly supplied to each coolant flow inlet  18 . At this time, if a discharge pressure of the liquid coolant from the coolant discharge ports  52  varies due to variation in discharge pressure of the pump or the like, amount of the liquid coolant supplied through the coolant flow inlets  18  to the first and second cooling flow passages  41 ,  42  of the rotor core  21  varies. Consequently, there occurs variation in cooling performance of the rotor  20  with the liquid coolant. In addition, the liquid coolant discharged from the coolant discharge ports  52  is repelled at the coolant flow inlets  18 , and flows back; thus the flow of the liquid coolant is disturbed, and becomes unstable. 
     To the contrary, in the present embodiment, in order to prevent each coolant flow inlet  18  from opposing each coolant discharge port  52  in the rotor radial direction, the coolant flow inlets  18  are arranged such that the rotor axial position of each coolant flow inlet  18  deviates from the rotor axial position of each coolant discharge port  52 , thereby preventing the liquid coolant discharged from the coolant discharge ports  52  from being directly supplied to the coolant flow inlets  18 , temporarily storing the liquid coolant in the hollow part  17 , and then supplying the liquid coolant to the coolant flow inlets  18 . Through this configuration, it is possible to suppress direct influence of the flow of the liquid coolant discharged from the coolant discharge ports  52  onto the flow at the coolant flow inlets  18 . For example, even if the discharge pressure of the liquid coolant from the coolant discharge ports  52  varies due to variation in discharge pressure of the pump or the like, it is possible to suppress variation in amount of the liquid coolant supplied through the coolant flow inlets  18  to the first and second cooling flow passages  41 ,  42  of the rotor core  21 . It is possible to prevent the liquid coolant discharged from the coolant discharge ports  52  from being repelled at the coolant flow inlets  18  to flow back, thereby stabilizing a liquid level D of the liquid coolant stored in the hollow part  17 , thus stabilizing the flow of the liquid coolant toward the coolant flow inlets  18 . As a result, it is possible to suppress variation in cooling performance of the rotor  20  using the liquid coolant. 
     In the aforementioned embodiment, there has been described the example of disposing each coolant flow inlet  18  at a position deviating in the rotor axial direction from each coolant discharge port  52  so as to prevent each coolant flow inlet  18  from opposing each coolant discharge port  52  in the rotor radial direction. However, in the present embodiment, as shown in a cross sectional view of  FIG. 3  that is vertical to the rotor axial direction, for example, in order to prevent each coolant flow inlet  18  from opposing each coolant discharge port  52  in the rotor radial direction, the coolant flow inlets  18  may be arranged such that a rotor circumferential position of each coolant flow inlet  18  is different from a rotor circumferential position of each coolant discharge port  52  so as to locate each coolant flow inlet  18  at a position deviating in the rotor circumferential direction from each coolant discharge port  52 . In this case, it is also possible to suppress direct influence of the flow of the liquid coolant discharged from the coolant discharge ports  52  onto the flow at the coolant flow inlets  18 . Moreover, in the present embodiment, each coolant flow inlet  18  may be arranged at a position deviating in two directions of the rotor axial direction and the rotor circumferential direction from each coolant discharge port  52  so as to prevent each coolant flow inlet  18  from opposing each coolant discharge port  52  in the rotor radial direction. As aforementioned, in the present embodiment, each coolant flow inlet  18  may be arranged in a manner as to deviate in either one of the rotor axial direction and the rotor circumferential direction from each coolant discharge port  52 . 
     In the aforementioned embodiment, there has been described the example in which the coolant supply shaft  50  is integrally rotated with the rotor  20  and the rotor shaft  16  at the same rotational speed. However, in the present embodiment, the coolant supply shaft  50  may be supported by the rotor shaft  16  via bearings, or the like so that the coolant supply shaft  50  is rotated at a different rotational speed from that of the rotor  20  and the rotor shaft  16 . In the present embodiment, it may be configured that the coolant supply shaft  50  is fixed to the housing  60 , and the rotor shaft  16  is supported by the coolant supply shaft  50  via bearings, or the like so that the coolant supply shaft  50  is not rotated. 
     As aforementioned, the mode for carrying out the present invention has been explained, but the present invention is not limited to the aforementioned embodiment, and it is needless to mention that the present invention can be carried out in various modes without departing from the gist of the present invention.