Abstract:
A motor for a vehicle is installed in a railway train and has a fan that is mounted on a rotor shaft and that causes the outside air into the motor. The motor for a vehicle includes a stopper that is fixed in between a bearing, which supports the rotor shaft, and the fan, which is inserted from that side of the rotor shaft at which the bearing lies. The stopper is configured to fit with the fan. The fan has a linear expansion coefficient set to be greater than linear expansion coefficients of the rotor shaft and the stopper. The fan is configured to be fittable with the stopper using bolts that are inserted from outside toward the stopper.

Description:
FIELD 
       [0001]    The present invention is related to a motor for a vehicle that drives a railroad vehicle, and is particularly related to the configuration of an outer fan. 
       BACKGROUND 
       [0002]    Generally, when a motor gets heated due to the heat generated during the passage of electric current, the deterioration of an insulator is accelerated and causes a decrease in longevity or efficiency. Hence, it is necessary to cool down the inside of the motor. Particularly in recent years, there has been a development of totally-enclosed-fan-cooled motors that include an outer fan, which is fixed to a rotor shaft at the end lying on the outside of the housing, and an inner fan, which agitates the air inside the motor. Particularly, by taking into consideration the issue of maintenance from outside, it is common practice to fix the outer fan with bolts that are fitted by insertion in the direction of the rotor shaft. 
         [0003]    In the conventional technology represented by Patent Literature 1 mentioned below, a fan that is fixed to a rotor shaft in an identical manner as described above rotates so as to let the outside air in and to let the heat out from the inside of the motor. As a result, the motor gets cooled down in an effective manner. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent Literature 1: Japanese Patent Application Laid-open No. H05-300698 
       
     
       SUMMARY 
     Technical Problem 
       [0005]    In the conventional technology represented by Patent Literature 1 mentioned above, the fan is bolted to a shaft retainer (stopper) or bolted to the end face of a rotor shaft. However, bolt insert holes formed on the fan have a larger diameter than the diameter of the bolts. For that reason, in case the rotor shaft is subjected to torque variation equal to or greater than the frictional force of the bolting, then the centers of the bolts shift with respect to the bolt insert holes. That sometimes leads to the loosening of the bolts, which eventually causes the bolts to break. In that case, the fan may get unfastened. 
         [0006]    The present invention has been made to solve the above problems in the conventional technology and it is an object of the present invention to provide a motor for a vehicle that is configured in such a way that, at normal temperature, the fan can be easily taken out and, at a high temperature or at a low temperature, the fan can be prevented from skidding that may occur due to the torque variation of the rotor shaft. 
       Solution to Problem 
       [0007]    A motor for a vehicle according to an aspect of the present invention installed in a railway train and having a fan that is mounted on a rotor shaft and that causes the outside air into the motor, the motor for a vehicle including: a stopper which functions as a positioning member for the fan in an axial direction, which is fixed in between a bearing supporting the rotor shaft and the fan inserted from one end of the rotor shaft, and which has a surface formed opposite to the fan so as to be fittable with the fan, wherein the fan is fixed by a fastening member, which is inserted toward the stopper in substantially parallel to the rotor shaft, and has a linear expansion coefficient set to be greater than linear expansion coefficients of the rotor shaft and the stopper. 
       Advantageous Effects of Invention 
       [0008]    According to an aspect of the present invention, a fan, which is made from a material having a greater linear expansion coefficient than the linear expansion coefficient of a rotor shaft and a stopper, is made to fit in the stopper. Hence, at normal temperature, the fan can be easily taken out and, at a high temperature or at a low temperature, the fan can be prevented from skidding that may occur due to the torque variation of the rotor shaft. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is a vertical cross-sectional view of a motor with a central focus on a fan. 
           [0010]      FIG. 2  is a vertical cross-sectional view explaining a configuration of the motor fan according to a first embodiment. 
           [0011]      FIG. 3  is a diagram illustrating a condition in which the motor fan illustrated in  FIG. 2  is fixed to a rotor shaft. 
           [0012]      FIG. 4  is a cross-sectional view taken along line A-A illustrated in  FIG. 3 . 
           [0013]      FIG. 5  is a diagram explaining a relationship between linear expansion coefficients and the brake torque. 
           [0014]      FIG. 6  is a vertical cross-sectional view explaining a configuration of the motor fan according to a second embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0015]    Exemplary embodiments of a motor for a vehicle to the present invention are described below in detail with reference to the accompanying drawings. The present invention is not limited to these exemplary embodiments. 
       First Embodiment 
       [0016]      FIG. 1  is a vertical cross-sectional view of a motor  100  with a central focus on a fan  30 ;  FIG. 2  is a vertical cross-sectional view explaining a configuration of the fan  30  according to a first embodiment;  FIG. 3  is a diagram illustrating a condition in which the fan  30  illustrated in  FIG. 2  is fixed to a rotor shaft;  FIG. 4  is a cross-sectional view taken along line A-A illustrated in  FIG. 3 ; and  FIG. 5  is a diagram explaining a relationship between the linear expansion coefficients and the brake torque. 
         [0017]    It is illustrated in  FIG. 1  that, in the motor  100 , the fan  30  is fixed to a rotor shaft  10  with bolts (fastening members)  40 , and a stopper  20  serving as a positioning member for the fan  30  in the axial direction is disposed in between the fan  30  and a bearing  50 . 
         [0018]    Given below with reference to  FIGS. 2 to 5  is the explanation related to a configuration of the fan  30  illustrated in  FIG. 1 . The fan  30  has a boss section (a protruding section)  31  that fits, along the axial direction, in a recessed portion  21  of the stopper  20  for the bearing  50 . Besides, upon fitting in the stopper  20 , the fan  30  fits together with the rotor shaft  10 . Meanwhile, the rotor shaft  10  and the stopper  20  are made from, for example, iron; while the fan  30  is made from, for example, aluminum. Moreover, regarding the linear expansion coefficient of each member and regarding the transmission of rotary torque, the explanation is given later. 
         [0019]    Given below are the dimensions of a contact portion in each member. Herein, the diameter in the lateral direction of the rotor shaft  10  (hereinafter, referred to as “rotor shaft diameter D”); the diameter of the recessed portion  21  of the stopper  20  (hereinafter, referred to as “fan-abutting-face diameter ds”); the diameter of that portion of the fan  30  which makes contact with the rotor shaft  10  (hereinafter, referred to as “rotor-shaft-abutting-face diameter df 1 ”); and the diameter of the boss section  31  that fits in the recessed portion  21  of the stopper  20  (hereinafter, referred to as “stopper-abutting-face diameter df 2 ) are illustrated. 
         [0020]    The bolts  40  illustrated in  FIG. 4  are threaded into the stopper  20  through bolt insert holes that are formed on the fan  30 . With the bolts  40 , the fan  30  and the stopper  20  are fixed. Meanwhile, the stopper  20  is fit to the rotor shaft  10  by means of shrink fitting. 
         [0021]    In the A-A cross-sectional view illustrated in  FIG. 4 , the rotor shaft  10 , the boss section  31 , and the stopper  20  are conceptually illustrated to be in a fitted condition at normal temperature. A small gap is illustrated in between the fitted portions of the members. Herein, the boss section  31  is disposed on the outside of the rotor shaft  10  and on the inside of the stopper  20 . That is, the boss section  31  is sandwiched between the rotor shaft  10  and the stopper  20 . 
         [0022]    In between the inner periphery of the boss section  31  and the outer periphery of the rotor shaft  10 , a gap is illustrated that is present at normal temperature. In an identical manner, in between the outer periphery of the boss section  31  and the inner periphery of the stopper  20 , a gap is illustrated that is present at normal temperature. The motor  100  according to the first embodiment is configured in such a manner that, due to the difference in the linear expansion coefficients of the members at a low temperature or at a high temperature, the contact pressure at the fitted portions is increased so as to vary the brake torque between the members. 
         [0023]    That point is explained below in details. With reference to  FIG. 2 , for example, when the ambient temperature around the fan  30  decreases, then the rotor-shaft-abutting-face diameter df 1  becomes smaller than the rotor shaft diameter D because the contraction amount of the fan  30  (made from, for example, aluminum) is greater than that of the rotor shaft  10  (made from, for example, iron). Thus, it results in an increase in the contact pressure between a rotor shaft abutting face  32  and the rotor shaft  10 . 
         [0024]    With the rise in the ambient temperature around the fan  30 , the stopper-abutting-face diameter df 2  becomes greater than the fan-abutting-face diameter ds because the contraction amount of the fan  30  (made from, for example, aluminum) is greater than that of the stopper  20  (made from, for example, iron). Thus, it results in an increase in the contact pressure between the boss section  31  and the stopper  20 . 
         [0025]    Explained below with reference to  FIG. 5  is the relationship between the linear expansion coefficients and the brake torque using calculating formulae. Firstly, it is defined that the portion over which the rotor shaft  10  and the boss section  31  make contact has a diameter d 1 , the portion over which the boss section  31  and the stopper  20  make contact has a diameter d 2 , and the stopper has a diameter d 3 . In this case, a linear expansion coefficient αAl of aluminum and a linear expansion coefficient αFe of iron can be expressed as given in Expression (1). 
         [0000]      linear expansion coefficients:αAl&gt;αFe  (1)
 
         [0026]    A temperature change ΔT can be expressed as given in Expression (2). 
         [0000]      temperature change:Δ T=T−Tr (where,  Tr :normal temperature)  (2)
 
         [0027]    A difference δ between the linear expansion coefficient αAl of aluminum and the linear expansion coefficient αFe of iron can be expressed as given in Expressions (3) and (4). 
         [0000]      δ d   1 =(αAl−αFe) d   1   ΔT   (3)
 
         [0000]      δ d   2 =(αFe−αAl) d   2   ΔT   (4)
 
         [0028]    When the temperature change ΔT&gt;0, the difference δ between the linear expansion coefficient αAl of aluminum and the linear expansion coefficient αFe of iron can be expressed as given in Expressions (5) and (6). 
         [0000]      when Δ T&gt; 0, δd   1 &gt;0, δd   2 &lt;0  (5)
 
         [0000]      when Δ T&lt; 0, δd   1 &lt;0, δd   2 &gt;0  (6)
 
         [0029]    Thus, at a high temperature, aluminum and iron abut against each other (being in a shrink-fit condition) at the diameter d 2  of the portion over which the boss section  31  and the stopper  20  make contact. Moreover, at a low temperature (for example, when the motor  100  is started at a place in a cold weather region), aluminum and iron abut against each other (being in a expansion-fit condition) at the diameter d 1  of the portion over which the rotor shaft  10  and the boss section  31  make contact. 
         [0030]    A contact pressure PQ of aluminum and iron can be expressed as given in Expressions (7) and (8). 
         [0000]                             when                 Δ                 T     &gt;   0     ,     
            P   Q     =         δ                   d   2       2          {           1   EAl     ·       d   2     2            (           d   1   2     +     d   2   2           d   2   2     -     d   1   2         -   vAl     )       +         1   EFe     ·       d   2     2            (           d   2   2     +     d   3   2           d   3   2     -     d   2   2         -   vFe     )         }                 where, EAl:Young&#39;s modulus of Al, EFe:Young&#39;s modulus of Fe, ν:Poission ratio  (7)
 
         [0000]    
       
         
           
             
               
                 
                   
                       
                   
                    
                   
                     
                       
                         when 
                          
                         
                             
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         T 
                       
                       &lt; 
                       0 
                     
                     , 
                     
                       
 
                     
                      
                     
                       
                         P 
                         Q 
                       
                       = 
                       
                         
                           
                             δ 
                              
                             
                                 
                             
                              
                             
                               d 
                               1 
                             
                           
                           2 
                         
                          
                         
                           { 
                           
                             
                               
                                 
                                   1 
                                   EFe 
                                 
                                 · 
                                 
                                   
                                     d 
                                     1 
                                   
                                   2 
                                 
                               
                                
                               
                                 ( 
                                 
                                   1 
                                   - 
                                   vFe 
                                 
                                 ) 
                               
                             
                             + 
                             
                               
                                 
                                   1 
                                   EAl 
                                 
                                 · 
                                 
                                   
                                     d 
                                     1 
                                   
                                   2 
                                 
                               
                                
                               
                                 ( 
                                 
                                   
                                     
                                       
                                         d 
                                         1 
                                         2 
                                       
                                       + 
                                       
                                         d 
                                         2 
                                         2 
                                       
                                     
                                     
                                       
                                         d 
                                         2 
                                         2 
                                       
                                       - 
                                       
                                         d 
                                         1 
                                         2 
                                       
                                     
                                   
                                   - 
                                   vAl 
                                 
                                 ) 
                               
                             
                           
                           } 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
           
         
       
     
         [0031]    At the diameter d 2  of the portion over which the boss section  31  and the stopper  20  make contact, a brake torque T can be expressed as given in  FIG. 9 . At the diameter d 1  of the portion over which the rotor shaft  10  and the boss section  31  make contact, the brake torque T can be expressed as given in Expressions (9) and (10). 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       when 
                        
                       
                           
                       
                        
                       Δ 
                        
                       
                           
                       
                        
                       T 
                     
                     &gt; 
                     0 
                   
                   , 
                   
                     
 
                   
                    
                   
                     T 
                     = 
                     
                       μ 
                        
                       
                           
                       
                        
                       
                         P 
                         Q 
                       
                        
                       
                         
                           A 
                           1 
                         
                         · 
                         
                           
                             d 
                             2 
                           
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   9 
                   ) 
                 
               
             
           
         
       
     
         [0032]    where, μ: friction coefficient
       A 1 : lateral area of outer diameter d 1         
 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       when 
                        
                       
                           
                       
                        
                       Δ 
                        
                       
                           
                       
                        
                       T 
                     
                     &lt; 
                     0 
                   
                   , 
                   
                     
 
                   
                    
                   
                     T 
                     = 
                     
                       μ 
                        
                       
                           
                       
                        
                       
                         P 
                         Q 
                       
                        
                       
                         
                           A 
                           1 
                         
                         · 
                         
                           
                             d 
                             1 
                           
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   10 
                   ) 
                 
               
             
           
         
       
     
         [0034]    where, A 2 : lateral area of outer diameter d 2    
         [0035]    In this way, the motor  100  according to the first embodiment is configured in such a way that, at a low temperature, the contact pressure PQ at the abutting portion between the rotor shaft abutting face  32  and the rotor shaft  10  increases thereby leading to the generation of the brake torque T between the rotor shaft  10  and the fan  30 . Moreover, the configuration is such that, at a high temperature, the contact pressure PQ at the abutting portion between the boss section  31  and the stopper  20  increases thereby leading to the generation of the brake torque T between the stopper  20  and the boss section  31 . 
         [0036]    In contrast, in a conventional motor, for example, the fan is directly fixed to the rotor shaft by using the fastening force of bolts. In that case, as also described above in the technical problem section, the torque of the rotor shaft acts directly on the bolts. That may lead to the loosening of the bolts. Moreover, in another type of configuration, the fan is fixed by inserting bolts in the stopper that is fit to the rotor shaft by means of shrink fitting. In that case too, the torque of the rotor shaft acts directly on the bolts. 
         [0037]    As described above, in the motor  100  according to the first embodiment, the fan  30  is made from a material having a greater linear expansion coefficient than the linear expansion coefficients of the rotor shaft  10  and the stopper  20 . Moreover, the boss section  31  of the fan  30  is sandwiched between the rotor shaft  10  and the stopper  20 . Hence, for example, at the temperature observed while running, in addition to the fastening force of the bolts  40 , it is also possible to apply the brake torque T in the rotating direction irrespective of whether the temperature is high or low. Consequently, for example, at the temperature when the maintenance of the fan  30  is done (i.e., at a normal temperature Tr), the fan  30  can be detached without difficulty. Moreover, if the bolts  40  become loose at a low temperature, the fan can still be prevented from skidding that may occur due to torque variation. Furthermore, since the load on the bolts  40  decreases, it becomes possible to reduce the number of the bolts  40  or to downsize the bolts  40 . Besides, since it is sufficient only to process the fitted portion between the stopper  20  and the boss section  31 , the configuration of the abutting portion of the fan  30  can be simplified. As a result, the fan  30  can become lighter in weight, can be installed in a smaller space, and can be manufactured at low cost. 
       Second Embodiment 
       [0038]    In the motor  100  for a vehicle according to a second embodiment, the stopper  20  and the boss section  31  have a different shape. Explained below is a configuration of the fan according to the second embodiment. Meanwhile, the elements identical to those explained in the first embodiment are referred to by the same reference numerals and their explanation is not repeated. Only the difference in the configuration is explained below. 
         [0039]      FIG. 6  is a vertical cross-sectional view for explaining a configuration of the fan  30  according to the second embodiment. As illustrated in  FIG. 6(   a ), the boss section  31  fits in a groove portion of the stopper  20 . With the boss section  31 , the stopper  20 , and the rotor shaft  10  configured in such a manner; at a high temperature, the outer periphery of the boss section  31  makes contact with the stopper  20 . Moreover, at a low temperature, the fan  30  makes contact with the rotor shaft  10  and the inner periphery of the boss section  31  makes contact with the stopper  20 . 
         [0040]    As illustrated in  FIG. 6(   b ), a stopper boss section  33  has a shape that fits in a groove portion of the fan  30 . Thus, with the stopper boss section  33 , the stopper  20 , and the rotor shaft  10  configured in such a manner; at a low temperature, the fan  30  makes contact with the rotor shaft  10  and the outer periphery of the stopper boss section  33  makes contact with the fan  30 . Moreover, at a high temperature, the inner periphery of the stopper boss section  33  makes contact with the fan  30 . 
         [0041]    As described above, in the motor  100  according to the second embodiment, the thickness of the fitted portion between the stopper  20  and the fan  30  is reduced as compared to the first embodiment. That makes it possible to reduce the difference between the brake torque T at the high temperature and the brake torque T at the low temperature. 
         [0042]    Meanwhile, in the explanation according to the first and second embodiments, it is assumed that the rotor shaft  10  and the stopper  20  are made from iron and the fan  30  is made from aluminum. However, that does not have to be the only case. Herein, it is sufficient that the linear expansion coefficient α is set to be greater than the linear expansion coefficients α of the rotor shaft  10  and the stopper  20 . 
         [0043]    Moreover, the linear expansion coefficient α of the rotor shaft  10  and the linear expansion coefficient α of the stopper  20  can also be set to have different values. For example as illustrated in  FIG. 1 , the contact surface area between the recessed portion  21  and the boss section  31  is smaller than the contact surface area between the rotor shaft abutting face  32  and the rotor shaft  10 . However, if the linear expansion coefficient α of the stopper  20  is set to a value smaller than the linear expansion coefficient α of the rotor shaft  10 , the brake torque T at a high temperature can be secured. Meanwhile, the materials of the members need not be limited to aluminum and iron, and any other material can be used as long as the abovementioned relationship between the linear expansion coefficients α is established. 
         [0044]    In the first and second embodiments, the explanation is given with reference to an outer fan of a totally-enclosed-fan-cooled motor as an example. However, the explanation is not limited to the totally-enclosed-fan-cooled motor or to the outer fan, and is also applicable to a motor other than a totally-enclosed-fan-cooled motor or to a fan other than an outer fan. 
         [0045]    Moreover, in the first and second embodiments, the bolts  40  are used as the fastening members for the fan  30 . Alternatively, the fastening members are not limited to the bolts  40  as long as those fastening members can be threaded in the stopper  20  for fixing the fan  30 . 
       INDUSTRIAL APPLICABILITY 
       [0046]    In this way, the present invention is applicable to a motor for a vehicle that drives a railroad vehicle, and is particularly suitable as an invention in which, at a normal temperature, the fan can be easily taken out and, at a high temperature or at a low temperature, the fan can be prevented from skidding that may occur due to the torque variation of the rotor shaft. 
       REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               10  ROTOR SHAFT 
               20  STOPPER 
               21  RECESSED PORTION 
               30  FAN 
               31  BOSS SECTION 
               32  ROTOR SHAFT ABUTTING FACE 
               33  STOPPER BOSS SECTION 
               40  BOLT 
               50  BEARING 
               100  MOTOR 
             α LINEAR EXPANSION COEFFICIENT 
             D ROTOR SHAFT DIAMETER 
             df 1  ROTOR-SHAFT-ABUTTING-FACE DIAMETER 
             df 2  STOPPER-ABUTTING-FACE DIAMETER 
             ds FAN-ABUTTING-FACE DIAMETER 
             d 1  DIAMETER OF PORTION OVER WHICH ROTOR SHAFT AND BOSS SECTION MAKE CONTACT 
             d 2  DIAMETER OF PORTION OVER WHICH BOSS SECTION AND STOPPER MAKE CONTACT 
             d 3  STOPPER DIAMETER 
             T BRAKE TORQUE 
             Tr NORMAL TEMPERATURE 
             ΔT TEMPERATURE CHANGE