Abstract:
An assembled battery device comprising a plurality of single cells which are placed with a predetermined space between each of them and an element for detecting swelling is set in the predetermined space between the single cells and operates in accordance with the transformation of the single cells by swelling. Therefore, when a single cell swells and transforms, resulting from being overcharged, the element for detecting swelling is activated in accordance with such transformation and detects the state of overcharging.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an assembled battery device comprising a plurality of single cells, and a power supplying device using this assembled battery device. 
     BACKGROUND OF THE INVENTION 
     In general, a secondary battery, which can be recharged and used repeatedly, is used as an assembled battery in which a plurality of single cells is assembled depending on the load. When a single cell is overcharged during the charging of such an assembled battery, the life of the single cell could be adversely affected. Therefore, it is necessary to prevent each single cell from being overcharged during the charging process. 
     When a single cell is overcharged, some changes are brought about in the single cell including an increase in charge voltage over a predetermined voltage; an abnormal rise in temperature; or transformation of the surface by swelling, which results when a polar plate inside the single cell swells and accordingly pushes out on the surface. Monitoring these changes, therefore, allows the overcharging of a single cell to be detected. 
     There are several approaches for preventing the overcharging of a single cell. One of them is to monitor a single cell charge voltage on the side of a charging device during the charging of an assembled battery, in which when the charge voltage exceeds a predetermined voltage, the charging of the assembled battery will be terminated. In case of any failure of the charging device, however, it becomes impossible to stop charging on the basis of a single cell charge voltage. 
     Another approach is to detect the surface temperature of a single cell with a temperature sensor and the like, in which, when a surface temperature exceeds a predetermined temperature, the sensor will detect overcharging. Usually, however, there is a difference in temperature between the inside and the surface of a single cell, and also the surface temperature of a single cell is subject to changes of ambient temperature. Accordingly, it becomes difficult to grasp the definite temperature inside a single cell enough to shut off charging. 
     Another approach, as disclosed in publication of the unexamined Japanese patent application 2000-353552, is to house single cells in a container in which a space is left between the inner wall of the container and the surface of a single cell, and in which a switch is installed so as to operate by being pressed. According to this configuration, if a single cell is overcharged and then excess transformation by swelling occurs on the surface of the single cell, the switch will end up being pressed by the swollen single cell surface and this will lead to termination of charging. Thus, this approach allows the problems previously described to be prevented from occurring and makes detection of overcharge possible. 
     However, these types of assembled batteries usually require a ventilation space between single cells to help dissipate the heat from them. Therefore, the use of the above described configuration, where installation of the switch results in the need of a space between the inner wall of the container and each single cell, leads to an increase in size, and consequently concerns about a considerably large place for installation. 
     The present invention has been developed in view of such circumstances. It is an object of the invention to provide both an assembled battery device and a power supplying device using this assembled battery device so as to make the overcharging of a single cell surely detectable and avoid an increase in battery size. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present invention, an assembled battery device comprises a plurality of single cells with a predetermined space between them, and elements for detecting swelling of the cells. Each element is placed in the space between the single cells and activated in accordance with the transformation of the cells by swelling. According to this configuration, when a single cell swells and transforms due to overcharging, the element for detecting swelling is activated, so that overcharging can be detected. 
     When single cells of a cuboid shape are used, it is preferable to arrange them in such a manner that side walls having the largest area are placed opposite each other and an element for detecting swelling are put almost on the center part of the side wall having the largest area. This is because the degree of transform by swelling becomes maximum at the center part of the side wall having the largest area of any other side walls in a single cell. Installing an element for detecting swelling at this position, therefore, makes transform by swelling much more detectable. In addition, regarding the shape of a single cell, an ellipsoidal shape, where the cross section is an elliptic cylindrical shape, is also applicable. In case of single cells of this shape, side walls with a major axis are placed opposite each other and an element for detecting swelling is put almost on the center part of the side wall. Thus, as described above, transform by swelling can be detected at this position with much more certainty. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an assembled battery device in a power supplying device in accordance with a first embodiment of the present invention. 
         FIG. 2  is a perspective view of the assembled battery device in the power supplying device in accordance with the first embodiment of the present invention. 
         FIG. 3  is a perspective view of one single cell in the assembled battery device in accordance with the first embodiment of the present invention. 
         FIG. 4  is a circuit diagram of the power supplying device in accordance with the first embodiment of the present invention. 
         FIG. 5  is a circuit diagram of the power supplying device in accordance with a second embodiment of the present invention. 
         FIG. 6  is a perspective view of the assembled battery device in the power supplying device in accordance with a third embodiment of the present invention. 
         FIG. 7  is a circuit diagram of the power supplying device in accordance with the third embodiment of the present invention. 
         FIG. 8  is a perspective view of single cells of an ellipsoidal shape. 
         FIG. 9  is a perspective view of the assembled battery device in which single cells are arranged in two dimensional position. 
         FIG. 10  is a circuit diagram of the power supplying device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, a first embodiment in which a power supplying device of the present invention is embodied will be described with reference to  FIGS. 1 to 4 . In  FIG. 1 , the direction of the arrow A indicates the direction of depth. 
     The power supplying device in the first embodiment comprises an assembled battery device  1  which collectively houses a plurality of lithium-ion single cells  10  (hereinafter referred to as single cells  10 ) in a case  20 , and a charger  2  to charge these single cells  10 . 
     The case  20  has a fully open top surface and is a rectangular container shape longer in the direction of depth. In the four side walls of the case, a plurality of holes  21  of a square shape is pierced at a predetermined interval. In the case  20 , a plurality of single cells  10  are arranged in the direction of depth. These single cells  10  are placed with a space  30  between each single cell  10  so that the heat generated from the single cells  10  during charging can be dissipated readily. For example, generated heat flows together with the air passing through the space  30  and dissipates through the open top surface or the holes  21  in the case  20  to the outside atmosphere. 
     Each single cell  10  is a cuboid shape and the front and back walls of the single cell  10  have the largest area of any other side walls. On the top surface of the single cell  10 , positive and negative terminals  11  of a column shape are placed so as to be connected to the positive and negative electrode plates in the single cell  10 . For example, in a pair of single cells  10  adjoining longitudinally, connecting a positive terminal  11  of the forward single cell  10  and a negative terminal of the backward single cell  10  with an electric wire (not shown) allows these single cells  10  to be connected in series. Furthermore, in such series-connected single cells  10 , a negative terminal  11  of the forefront and a positive terminal  11  of the rear end are connected to a charger  2  with an electric wire and consequently, inside the charger  2 , connected to a charging circuit  5  (equivalent to a power supplying device described in Claim.) 
     On the center part of the front wall of a single cell  10 , a circuit board  4  is fixed with adhesive and the like. The circuit board  4  is equipped with a push button switch  41  with constant closed contact (equivalent to an element for detecting swelling), and a male connector  42  with two terminal fittings. The both ends of the push button switch  41  are connected respectively to the terminal fittings of the male connector  42 , with which a plurality of female connectors, not shown, is configured so as to be fitted. Through an electric wire connecting individual female connectors, push button switches  41  result in being connected in series each other. The series circuit of a plurality of push button switches  41  thus formed is connected to the charger  2  and, inside the charger  2 , connected in series to a DC power source  61  and a relay coil  62 A of a relay  62 . In addition, a relay switch  62 B of the relay  62  has constant opened contact, which is kept open when electricity is not being conducted to the relay coil  62 A, and is connected in series between the single cells  10  and the charging circuit  5 . The DC power source  61  and the relay  62  configure a charge stop circuit  6  (equivalent to a charge stop device described in Claim.) 
     Hereinafter, operation of the power supplying device involving the above configuration will be described. 
     During the charging of the single cells  10 , the charging circuit  5  monitors and controls voltages of the single cells  10  so that when each single cell  10  is fully charged to stand at a predetermined voltage, charging operation can be terminated. 
     When operational failure occurs during charge control in the charging circuit  5  for some reason, there is a risk that a single cell  10  is overcharged. If any of the single cells  10  should be overcharged, the side wall of the single cell  10  will swell out and transform due to a rise in internal pressure of the single cell  10 . Accordingly, the push button switch  41  on the single cell  10  will be pressed by contact with the neighboring single cell  10 , so that the position of the push button switch  41  will change from open to close. Then current supply to the relay coil  62 A will be shut off and the relay switch  62 B will open, and consequently charging operation to the single cell  10  will stop. 
     A single cell  10  can slightly transform even when it is not overcharged. Therefore, it is preferable to leave the space  30  at least 1 mm to avoid false detection. 
     In this embodiment, even if a single cell  10  is overcharged due to operational failure during charge control in the charging circuit  5 , the overcharge can be detected without fail by means of the push button switch  41 , and charging operation can be shut off. Furthermore, the push button switch  41  is placed in the space  30  which is originally set up for helping dissipate the heat from the single cells  10 , so that the assembled battery device can be provided without having an extra space for installation of the push button switch  41  and resultantly with no increase in size. 
     In addition, because the push button switch  41  is placed on the center part of the front wall, which holds the largest area of any other side walls in the single cell  10 , swelling can be surely detected. 
     In addition, the application of constant closed contact in the push button switch  41  allows failure of switching operation to be reduced. If a push button switch with constant open contact is used in corrosive atmosphere, corroded product material will adhere all over the contact under such condition that the contact is always kept open. Therefore, when the contact is closed, conduction may be disturbed and this could lead to failure of the performance of switching operation. By contrast, in case of a push button switch with constant closed contact, adhesion of corroded product material can be prevented in the place of contact, so that switching operation will be performed certainly with no fear of conduction disturbance. 
     Furthermore, when used plurally, push button switches with constant closed contact can be connected in series each other, which makes the circuit configuration easier. 
     SECOND EMBODIMENT 
     A second embodiment in which the power supplying device of the present invention is embodied will be described with reference to  FIG. 5 . In this embodiment, regarding the identical portion as the first embodiment, overlapping description will be omitted with identical code appended. 
     In this embodiment, by contrast with the first embodiment, push button switches  71  with constant opened contact are used and connected in parallel each other and, in addition, a relay switch  63 B with constant closed contact is used in the charge stop circuit  6 . 
     According to this embodiment, when none of the single cells  10  are overcharged and has transformation by swelling, the push button switch  71  remains in the open position, and then since current is not passing into a relay coil  63 A, power consumption can be reduced. 
     THIRD EMBODIMENT 
     A third embodiment in which the power supplying device of the present invention is embodied will be described with reference to  FIGS. 6 and 7 . In this embodiment, regarding the identical portion as the first embodiment, overlapping description will be omitted with identical code appended and, in addition, description regarding similar action/effect is also omitted. 
     In this embodiment, the arrangement of the single cells  10  differs from that of the first embodiment, where the single cells  10  are set in line in the direction of depth, or one dimensional position (see  FIG. 2 ). By contrast, this embodiment employs two dimensional position, where four single cells  10  are set in two lines in the direction of depth. In addition, on the center of the front wall of each single cell  10  which is placed in the backward position of the single cells  10  adjoining longitudinally, the circuit board  4  is fixed, where push button switches  41  are connected each other in series. 
     It is not intended that the technical scope of the present invention be limited to the embodiments described above, but rather that the following description, for example, be also included in the technical scope of the present invention. 
     (1) In the above described embodiments, as an element for detecting swelling, the push button switches  41  and  71  have been used but the detecting means are not limited to them. For example, transformation by swelling can be detected from the distance measured by means of a displace sensor to measure a distance between the side walls of neighboring single cells  10  according to changes in capacitance. 
     (2) In the above described embodiments, an element for detecting swelling has been installed on each single cell  10  but configuration is not limited to this manner. For example, a push button switch can be installed on any one of the single cells  10 , or a push button switch can be installed on every other single cell  10  or every two single cells  10 . 
     (3) In the above described embodiments, the single cells  10  of a cuboid shape have been used; however, an ellipsoidal shape is also applicable as shown in  FIG. 8 . In this case, the side walls along the major axis are placed opposite each other and the circuit board  4  is placed on the center part of the side wall, so that transform by swelling can be detected more surely. 
     (4) In the above described embodiments, the circuit board  4  has been fixed on the single cell  10  with adhesive; however, the circuit board  4  can be fixed on the single cell  10  with, for example, thermal contraction resin. 
     (5) In the third embodiment above described, the single cells  10  have been set in two lines in the direction of depth; however, it is possible to set them in three or more lines. For example, sixteen single cells  10  can be set in four lines in the direction of depth (see  FIGS. 9 and 10 .) 
     According to the present invention, an element for detecting swelling is so configured as to detect transform by swelling; therefore, even when a single cell is overcharged and transforms, the overcharging of the single cell can be detected certainly. 
     In addition, installing an element for detecting swelling in a space, which is originally left between single cells, eliminates the need for an extra space to set up the element for detecting swelling and, moreover, an exclusive space between the element for detecting swelling and an single cell to operate the element for detecting swelling, so that an increase in the size of an assembled battery device can be avoided.