Abstract:
In an air battery system, a decrease in power output and an increase in inner pressure during discharge are prevented even when deposition of the reaction product increases with the discharge and the volume of the electrolytic solution increases with progress of the reaction. The air battery system includes an air battery a reservoir tank to reserve electrolytic solution to be supplied to the air battery and a reaction product sump to store reaction product produced in the air battery, the reaction product sump provided between the air battery and the reservoir tank.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Japanese Patent Application No. 2011-229396, filed Oct. 19, 2011 and incorporated herein in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to an air battery system that includes an air battery and a reservoir tank for reserving electrolytic solution to be supplied to the air battery. 
       BACKGROUND 
       [0003]    An example of air batteries is disclosed in Japanese Patent Unexamined Publication No. Hei6-501128, where the air battery is referred to as a “cell”. The cell disclosed in Japanese Patent Unexamined Publication No. Hei6-501128 includes a cathode and an anode facing the cathode, a vertically extending electrolysis region between them and a housing to contain electrolyte. 
         [0004]    The housing includes a sump with an upper and a lower region, said sump being of a size to contain enough aluminum hydroxide precipitate so as to permit the cell to continue operating after saturation of the electrolyte has taken place, with provision for convective passage of electrolyte from the upper region of the sump to the electrolysis region and at least one channel for convective passage of electrolyte from the electrolysis region to the upper region of the sump. 
       SUMMARY OF INVENTION 
       [0005]    However, the unsolved problems with the above-described cell disclosed in Japanese Patent Unexamined Publication No. Hei6-501128 include a decrease in power output in the discharge, and an increase in inner pressure of the battery due to an expansion of electrolytic solution. These problems are caused by an increase in volume of the electrolytic solution with progress of the reaction because a reaction product is produced as a result of discharge of the battery. 
         [0006]    To cope with these problems, it is an object of the present invention to provide an air battery system which neither decreases in power output, nor increases in inner pressure, even when deposition of a reaction product increases as a result of discharge and the volume of electrolytic solution increases with progress of the reaction. 
         [0007]    According to the present invention aiming to solve the above-described problems, an air battery system includes an air battery and a reservoir tank to reserve electrolytic solution to be supplied to the air battery. In the embodiments herein, a reaction product sump to store a reaction product produced in the air battery is provided between the air battery and the reservoir tank. This reaction product sump is elastically deformable according to an increase of the inner pressure due to production of the reaction product. 
         [0008]    With this structure, the reaction product produced in the air battery can be stored in the reaction product sump. In this case, the reaction product sump elastically deforms according to an increase of the inner pressure due to production of the reaction product. Therefore, the inner pressure does not increase even when deposition of the reaction product increases as a result of discharge and the volume of the electrolytic solution increases with progress of the reaction. 
         [0009]    According to the present invention, the decrease in power output and the increase in inner pressure can be prevented even when deposition of the reaction product increases as a result of the discharge and the volume of the electrolytic solution increases with progress of the reaction. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a schematic explanatory view of an air battery system according to the first embodiment of the present invention. 
           [0011]      FIG. 2  is a schematic explanatory view of an air battery system according to the second embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0012]    Hereinafter, an embodiment of the present invention will be described with reference to the drawings.  FIG. 1  is a schematic explanatory view of an air battery system according to the first embodiment of the present invention. 
         [0013]    The air battery system A 1  according to the first embodiment of the present invention includes a battery holder  10 , a plurality of air batteries  20 , a pressure and vibration generator  40 , and a controller C. 
         [0014]    The battery holder  10  includes a reservoir tank  50  and attaching/detaching members  60  that also serve as reaction product sumps, in which the attaching/detaching members  60  are disposed integrally with the reservoir tank  50  on the upper side thereof in the direction of the gravity vector. This configuration can simplify the structure, and can also cause gravity fall of the reaction product (described below) down to the attaching/detaching members  60 . In the first embodiment, the air batteries  20 , the attaching/detaching members  60  and the reservoir tank  50  are arranged in descending order along the direction of the gravity vector. 
         [0015]    The reservoir tank  50  reserves the electrolytic solution W to be supplied to the air batteries  20  that are attached to the attaching/detaching members  60  (described in detail below), and is configured in the shape of a horizontally-long cuboid. The reservoir tank  50  has a suitable volume according to the size and number of the air batteries  20 . 
         [0016]    The attaching/detaching members  60  detachably hold the plurality of air batteries  20 , and have a sufficient volume to contain the reaction product produced in the attached air batteries  20 . This structure prevents the increase in inner pressure of the air batteries  20 . 
         [0017]    The “reaction product” is a hydroxide or an oxide that is produced as a result of discharge. 
         [0018]    In the first embodiment, four air batteries  20  can be attached at once, however the present invention is not limited thereto. 
         [0019]    The attaching/detaching members  60  of the first embodiment have an expandable/shrinkable structure that expands/shrinks according to the inner pressure. Specifically, the expandable/shrinkable structure is a bellows structure that elastically deforms according to an increase of the inner pressure due to production of the reaction product in the electrolytic solution and the like. However, the present invention is not limited to the bellows structure, and the attaching/detaching members  60  may have any structure that is expandable/shrinkable according to a change of the inner pressure due to the electrolytic solution and the like. 
         [0020]    Each of the air batteries  20  includes a cathode  22  and an anode  23  disposed on front and back faces (upper and lower faces in the figure) of a separator  21 , and a liquid tight/gas permeable membrane  24  (hereinafter, referred to as a “waterproof membrane”) laminated on the outer face of the cathode  22 , and is housed in a case  25 . 
         [0021]    Each of the cases  25  includes an injection opening at the lower end in the figure, and is open at one side. At each of the injection openings, a valve  26  is disposed which permits injection of the electrolytic solution by means of pressure. 
         [0022]    On each of the waterproof membranes  24 , aeration ensuring members  27  are disposed at regular intervals so as to ensure aeration gaps between air batteries  20  adjacent in the vertical direction. 
         [0023]    The pressure and vibration generator  40  of the first embodiment presses and vibrates the attaching/detaching members  60 . The pressure and vibration generator mechanism  40  includes, for example, a vibration motor, and is connected to vibrating and pressurizing plates  41  of the attaching/detaching members  60  so as to be capable of applying pressure and vibration to the attaching/detaching members  60 . 
         [0024]    The controller C includes a CPU (central processing unit) and an interface circuit, and has a function of driving the pressure and vibration generator mechanism  40  at given time intervals by running a suitable program. This function is referred to as a “pressurizing and vibrating means C1”. 
         [0025]    A “given time interval” refers to a given discharge time period, which is specifically set based on the amount of the reaction product and the like. By causing a vibration at the given time intervals, the produced reaction product can be prevented from being deposited in the air batteries  20 . 
         [0026]    In the first embodiment, a vibration is caused in the attaching/detaching members  60 . However, a vibration may be caused in the reservoir tanks  50 . 
         [0027]    In the air battery system A 1  with the above-described configuration according to the first embodiment, the pressure and vibration generator  40  presses the attaching/detaching members  60  to inject the electrolytic solution into the air batteries  20  through the valves  26 . 
         [0028]    The reaction product produced as a result of discharge is precipitated in the attaching/detaching members  60 , and the volume of the attaching/detaching members  60  increases (expands) due to the bellows structure (expandable/shrinkable structure). Therefore, an increase in inner pressure can be prevented. 
         [0029]    After the given time period has elapsed, the pressure and vibration generator  40  causes a vibration in the attaching/detaching members  60 . The vibration promotes circulation of the electrolytic solution  20  in the air batteries, and also promotes precipitation of the produced reaction product. 
         [0030]    Next, an air battery system A 2  according to the second embodiment of the present invention will be described with reference to  FIG. 2 .  FIG. 2  is a schematic explanatory view of the air battery system according to the second embodiment of the present invention. The same or similar components as those of the above-described embodiment are indicated by the same reference numbers, and the descriptions thereof are omitted. 
         [0031]    The air battery system A 2  according to the second embodiment of the present invention includes an air battery holder  100 , an air battery  110 , a pressure and vibration generator  40  and a controller C. The air battery holder  100  includes a reservoir tank  120  and an attaching/detaching member  130  that also serves as a reaction product sump. In the second embodiment, the attaching/detaching member  130  is disposed on a lateral side of the reservoir tank  120 . 
         [0032]    The reservoir tank  120  reserves electrolytic solution to be supplied to the air battery  110  that is attached to the attaching/detaching member  130  (described in detail below), and is configured in the shape of a vertically-long cuboid having a suitable volume according to the size of the air battery  110 . 
         [0033]    The attaching/detaching member  130  is disposed at an intermediate part of a side wall  121  of the reservoir tank  120 , detachably holds the air battery  110 , and has a sufficient volume to contain the reaction product produced in the attached air battery  110 . This structure prevents an increase in inner pressure of the air battery  110 . 
         [0034]    As with the above-described air batteries  20 , the air battery  110  includes a cathode and an anode disposed on front and back faces (upper and lower faces in the figure) of a separator, and a liquid tight/gas permeable membrane (hereinafter, referred to as a “waterproof membrane”) laminated on the outer face of the cathode. 
         [0035]    A supply pipe  112  for supplying the electrolytic solution is connected between a side part  131  of the attaching/detaching member  130  and a side part  111  of the air battery  110 . Specifically, one end of the supply pipe  112  is connected to the side part  131  of the attaching/detaching member  130 , and the other end is connected to the side part  111  of the air battery  110  at a position closer to the end opposite the attaching/detaching member  130 . At one end of the supply pipe  112 , a check valve  113  is disposed which opens only when the electrolytic solution is supplied to the air battery  110 . In the second embodiment, the check valve  113  serves as a backflow preventing member. 
         [0036]    In the air battery system A 2  with the above-described configuration, the pressure and vibration generator  40  presses the attaching/detaching member  130  so as to inject the electrolytic solution into the air battery  110  through the check valve  113 . 
         [0037]    By injecting the electrolytic solution into the air battery  110 , the reaction product in the air battery  110  is flushed out to the attaching/detaching member  130  together with the electrolytic solution and is then precipitated in the attaching/detaching member  130 . Meanwhile, the volume of the attaching/detaching member  130  increases (expands) due to its bellows structure, and thereby an increase in inner pressure can be prevented. If the pressure is released, the check valve  113  prevents the electrolytic solution in the air battery  110  from flowing back through the supply pipe  112 . 
         [0038]    After a given time period has elapsed, the pressure and vibration generator  40  causes a vibration in the reservoir tank  120 . The vibration promotes circulation of the electrolytic solution in the air battery  110 . 
         [0039]    The present invention is not limited to the above-described embodiments, and the following modifications may be made.
       In order to control the flow of the electrolytic solution from the air battery to the reaction product sump, a flow control valve may be provided.   The flow control valve includes a control valve with a throttle mechanism and a driver (actuator) that operates an inner valve of the control valve according to a control signal (operation signal). The flow control valve can be controlled by the controller C.   In the above-described embodiments, the reaction product sump is provided as a part of the reservoir tank. However they may be provided separately from each other.       
 
         [0043]    While the present invention is described in detail, in any case, the components of the above-described embodiments may be applied not only to their original embodiment but also to the other embodiments with or without modifications. Furthermore, these components may be combined suitably.