Abstract:
A air pressure adjuster includes: a rotary electric machine; a casing housing the rotary electric machine hermetically; and an in-casing air pressure adjuster for adjusting an internal air pressure using a drive force generated a difference between the internal air pressure and an outer pressure of the casing. The in-casing air pressure adjuster discharges the air from the inside of the casing to the outside of the casing when the internal air pressure is higher than the external air pressure by a first predetermined value.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the foreign priority benefit under Title 35, United States Code, §119(a)-(d) of Japanese Patent Application No. 2016-105471, filed on May 26, 2016 in the Japan Patent Office, the disclosure of which is herein incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
       [0002]    The present invention relates to an air pressure adjuster for rotary electric machine. 
       2. Description of the Related Art 
       [0003]    In an air pressure range where the human can live, a voltage at which a discharge starts between conductors placed in the ambient pressure decreases as the air pressure decreases according to Paschens law. Accordingly, a motor used in, for example, an electric vehicle, a hybrid vehicle, etc. may have a problem in that a discharging, etc. may occur though the motor has a sufficient insulation performance in the lowland because an insulation performance becomes insufficient at a highland. 
         [0004]    To compensate the decrease in the insulation performance caused by decrease in the ambient pressure, various technologies have been proposed. For example, JP 4639916 disclosed a technology in which a voltage applied to the motor is decreased when the ambient pressure becomes low. Further, JP 2008-228378 A disclosed a technology in which an air pressure in a room in which the motor is installed is increased with an air compressor. Further, JP 2012-105391 A disclosed a technology in which a tank stores a gas which is supplied to a motor case from the tank. 
         [0005]    However, any of the above-described technologies needs complicated structures, which invite an increase in cost of a vehicle, etc. carrying the motor. 
       SUMMARY OF THE INVENTION 
       [0006]    An aspect of the present invention provides an air pressure adjuster for rotary electric machine capable of keeping an insulation performance by a simple structure. 
         [0007]    An aspect of the present invention provides an air pressure adjuster comprising: 
         [0008]    a rotary electric machine; 
         [0009]    a casing housing the rotary electric machine hermetically; and 
         [0010]    an in-casing internal air pressure adjuster for adjusting an internal air pressure using a drive force generated by a difference between the internal air pressure and an external air pressure of the casing. 
         [0011]    The in-casing air pressure adjuster may discharge the air from the inside of the casing to the outside of the casing when the internal air pressure is higher than the external air pressure by a first predetermined value. This prevents an error such as detachment of an oil seal in the casing. 
         [0012]    The in-casing air pressure adjuster may introduce air from the outside to the inside of the casing when the outer pressure is higher than the internal air pressure by a second predetermined value. This prevents the inside of the casing from being a negative pressure (negative gage pressure) having a large absolute value. 
         [0013]    The in-casing air pressure adjuster may include: an elastic body; and a pressure-receiving valve body which opens and closes in accordance with the pressure force pushed by the elastic body. 
         [0014]    The in-casing air pressure adjuster may include: a diaphragm: a switching unit that makes switching between communication and non-communication states between the inside and the outside of the casing in accordance with a displacement of the diaphragms. 
         [0015]    The air pressure adjuster according to the present invention can maintain the insulation performance of the rotary electric machine with a simple configuration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective view of a motor system according to a first embodiment of the present invention. 
           [0017]      FIG. 2  is a cross sectional view of the in-casing air pressure adjuster according to the first embodiment. 
           [0018]      FIG. 3  is a cross sectional view of the in-casing air pressure adjuster according to a second embodiment. 
           [0019]      FIG. 4  is a cross sectional view according to a third embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
       [0020]      FIG. 1  is a perspective view of a motor system S according to a first embodiment of the present invention. 
         [0021]    The motor system (air pressure adjuster for a rotary electric machine) S is used in a vehicle such as an electric vehicle, and a hybrid vehicle. 
         [0022]    The motor system S includes a casing  10  having a substantially rectangular shape, a motor (rotary electric machine)  12 , a shaft  16 , gears  18 ,  20 , and an in-casing internal air pressure adjuster  30 . 
         [0023]    The motor  12  includes a stator  12   a , having a substantially hollow cylindrical shape, being fixed to an inside of the casing  10 , and a rotor  12   b  rotating relative to the stator  12   a . The rotor  12   b  is coupled to the gears  18 ,  20  through the shaft  16 . When the rotor  12   b  rotates, the shaft  16  and the gears  18 ,  20  rotate together. The casing  10  houses the motor  12 , the shaft  16 , and the gears  18 ,  20  hermetically. The in-casing internal air pressure adjuster  30  includes check valves  32 ,  34  which adjust the internal air pressure of the casing  10 . 
         [0024]      FIG. 2  is a cross-sectional view of the in-casing internal air pressure adjuster  30 . The check valve  32  includes a valve seat (pressure-receiving valve body)  32   c , a stop valve (pressure-receiving valve body)  32   b , and a spring (elastic body)  32   a  for pressing the stop valve  32   b  to the valve seat  32   c . Accordingly, the check valve  32  discharges the air in the casing  10  to the outside when an internal pressure P 1 , which is an internal air pressure in the casing  10 , is higher than an external air pressure P 0 , which is an air pressure outside the casing  10 , by more than a predetermined pressure difference ΔPA (first predetermined value). 
         [0025]    The external air pressure P 0  is an ambient pressure in the first embodiment. Further, it is preferable that the air pressure difference ΔPA at which the check valve  32  starts operation is in a range not lower than 0.01 MPa and not higher than 0.1 MPa and more preferable that the range is not lower than 0.03 MPa and not higher than 0.04 MPa. This is because when the internal pressure P 1  increases due to a temperature increase, etc. of the motor  12 , if the air pressure difference ΔPA is allowed to be accessibly high, an oil seal (not shown) is detached, etc. and when the pressure difference ΔPA is allowed to be excessively low, it becomes difficult to keep the sufficient internal pressure P 1  to keep the insulation performance. 
         [0026]    A check valve  34  includes a valve seat body  34   c  (pressure-receiving valve body), a stop valve  34   b  (pressure-receiving valve body), and a spring  34   a  (elastic body) for pressing the stop valve  34   b  on the valve seat body  34   c . Accordingly, the check valve  34  introduces the air to the inside of the casing  10  from the outside when the external air pressure P 0  is higher than the internal pressure P 1  by more than ΔPB (second predetermined value). 
         [0027]    The check valve  34  has a function of making the internal pressure P 1  closer to the external air pressure P 0  when the location is a lowland, etc. where the external air pressure P 0  is significantly high. Further, the check valve  34  prevents that the inside of the casing  10  has a negative air pressure from the outside when the casing  10  is rapidly cooled. Accordingly, it is preferable that the air pressure difference ΔPB at which the check valve  34  operates is set to have so small as possible as the situation allows in such a range that the check valve  34  does not open due to vibrations, etc. More specifically, it is preferable that the air pressure difference ΔPB is in such a range as to be not lower than 0.001 MPa and not higher than 0.01 MPa and further preferable that the air pressure difference ΔPB is in such a range as to be not lower than 0.003 MPa and not higher than 0.004 MPa. 
         [0028]    As described above, according to the first embodiment, because “ΔPA&gt;ΔPB” is set, when the external air pressure P 0  increases, the internal pressure P 1  tends to increase according to the external air pressure P 0 . On the other hand, when the external air pressure P 0  decreases, the internal pressure P 1  hardly decreases. Accordingly, though the external air pressure P 0  decreases at a highland, etc., the in-casing internal air pressure adjuster  30  can keep the internal pressure P 1  at a relative high value, it is possible to keep the insulation performance of the motor  12  with a simple structure. 
       Second Embodiment 
       [0029]    Next, the motor system according to the second embodiment is described below. 
         [0030]    A general structure of the second embodiment is the same as that of the first embodiment shown in  FIG. 1 . However, in the second embodiment, an in-casing internal air pressure adjuster  40  is installed to the casing  10  shown in  FIG. 3  in place of the in-casing internal air pressure adjuster  30  in the first embodiment. 
         [0031]    The in-casing internal air pressure adjuster  40  includes a diaphragm valve  41  and the check valve  32 . The diaphragm valve  41  includes an air chamber  42  and a switching device  43 . The air chamber  42  includes a diaphragm  42   a  which separates the external air pressure P 0  and the internal pressure P 1  and is displaced in accordance with an air pressure difference between the external air pressure P 0  and the internal pressure P 1 . 
         [0032]    The switching device  43  connected to the diaphragm  12   a  makes switching between communication and non-communication between outside and the inside of the casing  10  by the displacement according to the positional displacement of the diaphragm  42   a . More specifically, the switching device  43  makes communication between the external air and the internal air of the casing  10  when the external air pressure P 0  is higher than the internal pressure P 1  by the air pressure difference ΔPB or more. Further, the check valve  32  discharges the air inside the casing  10  when the internal pressure P 1  is higher than the external air pressure P 0  by the air pressure difference ΔPA or more similarly to the check valve  32  in the first embodiment. Values of the air pressure differences ΔPA, ΔPB are the same as those in the first embodiment. 
         [0033]    As described above, according to the second embodiment, though the external air pressure P 0  decreases at a highland, etc. the internal pressure P 1  can be maintained to have a higher value by the in-casing internal air pressure adjuster  40 , which can keep the insulation performance of the motor  12  with a simple structure. 
       Third Embodiment 
       [0034]    Next, a motor system according to a third embodiment is described below. 
         [0035]    A general structure of the third embodiment is the same as that of the first embodiment shown in  FIG. 1 . However, in the third embodiment, an in-casing internal air pressure adjuster  50  is installed to the casing  10  shown in  FIG. 4  in place of the in-casing internal air pressure adjuster  30  in the first embodiment. 
         [0036]    The in-casing internal air pressure adjuster  50  includes a porous valve  51  and the check valve  32 . The porous valve  51  includes an attaching part  52 , a ring-shape packing  54 , a porous membrane  56 , and a cover  58 . The attaching part  52  is formed in substantially hollow cylindrical shape inserted into a circular through hole  10   a  formed in the casing  10 . The attaching part  52  is formed to have a flange  52   a  at one end thereof (an upper end in  FIG. 4 ) and a stopper  52   b  at the other end. The ring-shape packing  54  is inserted between the flange  52   a  and the casing  10 . The flange  52   a  and the stopper  52   b  pinch the ring-shape packing  54  and the casing  10  with pressure. 
         [0037]    The attaching part  52  has an opening at the flange  52   a  and the porous membrane  56  having a circular disk shape covers the opening and is fixed to the flange  52   a  surrounding the opening. The cover  58  circumferentially covers the porous membrane  56  so as to allow the external air to be in contact with the porous membrane  56  to prevent a foreign material from being in contact with the porous membrane  56 . The porous membrane  56  has a function to allow the air to pass therethrough between the outside and the inside of the casing  10  when a difference (absolute value) between the internal air pressure P 1  and the external air pressure P 0  is equal to or higher than the air pressure difference ΔPB. 
         [0038]    Further, the check valve  32  discharges the air inside the casing  10  when the internal pressure P 1  is higher than the external air pressure P 0  by the air pressure difference ΔPA or more similarly to the check valve  32  in the first embodiment. Preferable values of the air pressure differences ΔPA, ΔPB are the same as those in the first embodiment. As the porous valve  51 , Vent Filters having a name of TEMISH (registered trademark) or CAPSEAL (trademark) by NITTO DENKO CORPORATION are usable. 
         [0039]    As described above, according to the third embodiment, though the external air pressure P 0  decreases due to a highland, etc., it is possible to keep the internal air pressure P 1  at a relatively high value, so that the insulation performance of the motor  12  can be maintained with a simple structure similarly to the first embodiment. 
       Modifications 
       [0040]    The present invention is not limited to the above-described embodiments and may be modified in various modifications. The present invention is not limited to the configuration including all elements described in the above-described embodiments. Further, a part of a configuration of one of the embodiments can be replaced with a corresponding element in another embodiment or added to another embodiment. Further, a part of a configuration of one of the embodiments can be omitted, and another configuration may be added or replaced with. For example, there are modifications as follows: 
         [0041]    In the above-described embodiments, the external air pressure P 0  is “ambient air pressure”. However, any air pressure other than the ambient air pressure may be applied. For example, in a case where the above-described embodiments are applied to a hybrid vehicle, the in-casing internal air pressure adjuster  30  is installed in an air flow passage for air compressed by a super charger. In this case, “external air pressure P 0 ” is a pressure of air compressed by a supercharger. 
         [0042]    Further, the motor systems according to the first to third embodiments are applicable to not only electric vehicles, hybrid vehicles, etc. but also various electric products and plant equipment.