Patent Publication Number: US-2009220852-A1

Title: Battery pack secured by end plates

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a battery pack where a plurality of cylindrical batteries are contained in a battery holder and disposed in a fixed position, and particularly to a battery pack which is optimal as a power source mounted on a vehicle to supply electric power to a motor for driving the vehicle. 
     2. Description of the Related Art 
     Like in the case of a power source for a vehicle, a battery pack requiring larger output power has a multitude of batteries connected in series or in parallel. In order to retain the multitude of batteries in a fixed position, such battery pack is accommodated in a plastic-made battery holder. In order to accommodate the multitude of batteries in multiple tiers or rows, the battery holder accommodates the batteries disposed in a matrix or offset arrangement in a mutually parallel posture. The battery holder accommodating the multitude of batteries is so shaped as to have its opposite ends opened to be provided with an insertion portion for each of the batteries to be inserted in, and thus the multitude of batteries can be inserted into a single piece of battery holder to be disposed in a fixed position. A battery pack thus structured is described in JP No. 2004-171856-A. 
       FIG. 1  is an exploded perspective view of the battery pack described in JP No. 2004-171856-A. This battery pack has an end plate  93  secured respectively to opposite sides of the battery holder  92 . The battery holder  92  has a battery storage portion  94  opened at opposite ends to accommodate a multitude of cylindrical batteries  91  disposed in a matrix arrangement. In the battery pack shown in  FIG. 1 , the battery holder  92  is divided into two parts in the longitudinal direction (in the vertical direction when viewed in the drawing) of the cylindrical battery  91 , with the battery holder  92  being composed of an upper holder  92 A and a lower holder  92 B. The battery holder  92  has the upper holder  92 A and the lower holder  92 B mutually connected to accommodate the multitude of cylindrical batteries  91  in the battery storage portion  94 . In a state that the cylindrical batteries  91  are inserted in the battery storage portions  94  of the upper holder  92 A and the lower holder  92 B, the battery holder  92  mutually connects the upper holder  92 A and the lower holder  92 B to constitute the battery holder  92 . The upper holder  92 A and the lower holder  92 B are connected and secured by means of a connection member (not shown). The upper holder  92 A and the lower holder  92 B are provided with a ridge  95  projecting outside the peripheral walls, for the connection member to be inserted into the ridge  95 . 
     Further, the battery pack is so constructed and arranged that while the multitude of cylindrical batteries  91  are connected by means of a connection plate  96  connected to the terminal electrode of the cylindrical battery  91  which is exposed out of openings at the opposite faces of the battery holder  92 , the end plate  93  is secured to opposite faces of the battery holder  92 , and the opposite faces of the battery holder  92  are respectively sealed by the end plate  93 . The end plate  93  is fitted in and positioned at the periphery of the openings on the opposite faces of the battery holder  92 , and is then secured by ultrasonically welding the peripheral edge of the end plate  93  in joint with the periphery of the openings of the battery holder  92 . 
     The battery holder  92  thus structured is disadvantageous in that its contour becomes larger due to the structure of having the connection member. Further, since the battery holder  92  is welded to be connected with the end plate  93 , the structure of accommodating the multitude of batteries suffers the disadvantage that it is difficult to connect the battery holder  92  and the end plate  93  in a firm, strong manner. In particular, since the battery holder  92  and the end plate  93  are connected by welding the peripheral edge of the end plate  93  in joint with the periphery of the opening of the battery holder  92 , such arrangement suffers the disadvantage that connection strength becomes weaker at the center portion of the end plate  93 . For example, the battery pack shown in  FIG. 1  accommodates the batteries in two rows. Suppose that the battery pack were so structured as to accommodate the batteries in three or more rows. The wider an interval between the welded portions where the battery holder and the opposing end plate are mutually welded, the weaker the mechanical strength of such structure in aiming at firmly securing the end plate to the battery holder. To avoid such disadvantage, if the end plate is to be formed thicker in obtaining a wider welded portion, such formation will inevitably involve a higher cost of manufacture as well as a heavier and larger structure. 
     The present invention has been made to overcome the above described drawbacks. It is a primary object to provide a battery pack that effectively utilizes a space existing among cylindrical batteries and enables a pair of end plates to be firmly secured to a battery holder. Further, another vital object of the present invention is to provide a battery pack that effectively utilizes a structure of efficiently cooling each of the batteries and enable the end plates to be firmly secured to the battery holder, without the contour of the peripheral wall being enlarged. 
     SUMMARY OF THE INVENTION 
     The battery pack includes a plurality of cylindrical batteries  1  and a plastic-made battery holder  2 ,  52  accommodating the plurality of batteries  1  disposed in a matrix or offset arrangement in a mutually parallel posture. The battery holder  2 ,  52  includes a holder main body  10  accommodating the cylindrical batteries  1  and an end plate  20 ,  60  respectively connected to opposite ends of the holder main body  10 . Further, the holder main body  10  has a plurality of opposed walls  12  disposed in a mutually parallel posture inside peripheral walls  11 , and also has a storage portion  13  accommodating the plurality of cylindrical batteries  1  between the opposed walls  12 . Furthermore, the opposed wall  12  is provided, on its opposite faces, with a protrusion  14  projecting toward the swale between the adjacent cylindrical batteries  1  to constitute a thick portion  15 , and the thick portion  15  defines a through hole  16  extending through in the longitudinal direction of the cylindrical battery  1 . In the battery pack, a connection rod  8  is inserted in the through hole  16  defined in the thick portion  15  of the holder main body  10 , and the end plate  20 ,  60  is secured to the opposite ends of the holder main body  10  by means of the connection rod  8 . 
     In the battery pack structured as above, effective utilization of the space defined between the cylindrical batteries enables the pair of end plates to be firmly secured to the battery holder. This is because the opposed walls are respectively provided with the thick portion projecting toward the swale between the adjacent cylindrical batteries, a through hole is defined in the thick portion, and thus the connection rod is inserted through the through hole to secure the end plate. Further, when the protrusion is provided so as to project toward the swale between the adjacent cylindrical batteries and the thick portion is provided to the opposed wall, such structure also realizes the characteristic of enabling the end plate to be firmly secured to the battery holder, without enlarging the contour of the peripheral wall while effectively utilizing the structure of efficiently cooling each of the batteries. This is because the provision of the protrusion to the opposed wall enables the inner surface of the opposed wall to approach the surface of the cylindrical battery so as to accelerate the velocity of the fluid flowing between the opposed wall and the cylindrical battery. Particularly, such structure carries the characteristic that because the connection rod is inserted through the thick portion made up by the protrusion for efficiently cooling the battery, the end plate can be firmly secured while the cylindrical batteries being disposed to be mutually closer and without the peripheral wall being enlarged. 
     The battery pack described above, further, carries the characteristic that when a battery pack is structured to accommodate the batteries in multi tiers of more than three tiers, the end plate can also be firmly secured to the battery holder. This is because the middle portion of the end plate can be connected for securing operation. 
     In the battery pack of the present invention, a cooling gap  7  is defined between the opposed wall  12  and the cylindrical battery  1  to cause the fluid to flow for cooling the battery, and thus the cylindrical battery can be efficiently cooled in a wider area. 
     In the battery pack of the present invention, a cooling medium is forcibly blown through the through hole  16  to cool the cylindrical battery  1  in the storage portion  13 , and thus the cylindrical battery can be efficiently cooled via the battery holder. 
     In the battery pack of the present invention, the end plate  20 ,  60  is so structured as to have a fitting-on portion  22  for disposing a bus bar  5  in a fixed position, the bus bar  5  being connected to a terminal electrode  6  of the cylindrical battery  1  accommodated in the holder main body  10 , and thus the bus bar can be disposed in a fixed position by means of the end plate. 
     Further, in the battery pack of the present invention, the end plate  20  can be so structured as to have an insertion retainer  27  for inserting and retaining the end of the cylindrical battery  1  in a fixed position, the cylindrical battery  1  being accommodated in the storage portion  13  of the holder main body  10 . The battery pack enables the cylindrical battery to be disposed in a fixed position by means of the end plate. Particularly in this structure, when so structured as to have a cooling gap around the surface of the cylindrical battery, the cylindrical battery can have an accurate cooling gap around the surface of the cylindrical battery for an efficient cooling operation. 
     Furthermore, in the battery pack of the present invention, the holder main body  10  can be so structured as to have a retention protrusion  29  for retaining the inserted cylindrical battery  1  in a fixed position, the retention protrusion  29  being on the inner surface of the storage portion  13 . The battery pack enables the cylindrical battery to be disposed in a fixed position by inserting the battery through the battery holder. 
     The above and further objects of the present invention as well as the features thereof will become more apparent from the following detailed description to be made in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view showing a conventional type of battery pack; 
         FIG. 2  is a perspective view of the battery pack in accordance with an embodiment of the present invention; 
         FIG. 3  is an enlarged, horizontal, sectional view of the battery pack shown in  FIG. 2 ; 
         FIG. 4  is a perspective view of the battery holder for the battery pack shown in  FIG. 2 ; 
         FIG. 5  is a perspective view of the holder main body for the battery holder shown in  FIG. 4 ; 
         FIG. 6  is a perspective view of the end plate for the battery holder shown in  FIG. 4 ; 
         FIG. 7  is a vertical, latitudinal, sectional view of the battery pack shown in  FIG. 2 , and is a view corresponding to the sectional view taken along line A-A in  FIG. 3  and  FIG. 4 ; 
         FIG. 8  is a horizontal, latitudinal, sectional view of the battery pack shown in  FIG. 2 , and is a view corresponding to the sectional view taken along line B-B in  FIG. 3  and  FIG. 4 ; 
         FIG. 9  is a perspective view showing an alternative example of the battery holder; and 
         FIG. 10  is a perspective view showing the end plate for the battery holder shown in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     The battery pack shown in  FIG. 2  through  FIG. 8  includes a plurality of cylindrical batteries  1  and a plastic-made battery holder  2  accommodating the plurality of cylindrical batteries  1  disposed in a matrix or offset arrangement in a mutually parallel posture. Further, the battery pack shown in  FIGS. 2 ,  3 ,  7  and  8  includes an outer casing  3  for accommodating the battery holder  2 , and a cooling duct  4  is provided between the outer casing  3  and the battery holder  2 . 
     The cylindrical battery  1  to be used can be any kind of rechargeable battery such as a nickel-hydrogen battery and a lithium-ion battery. The cylindrical battery  1  shown in  FIG. 8  is composed of two pieces of unit cells  1 A interconnected linearly, and has terminal electrodes  6  secured at the opposite ends, to which a bus bar  5  is connectable. It is also practical and practicable that the cylindrical battery  1  is composed of either a single piece of battery or three or more pieces of batteries. 
     The outer casing  3  is a metallic casing and is composed of a bottom casing  31 , a top casing  32  connected to a side wall  31 A of the bottom casing  31 , and an end face plate  33  for respectively sealing the opposite apertures defined by the bottom casing  31  and the top casing  32 . The bottom casing  31  is fabricated by folding a metallic plate into a shape of having a side wall  31 A respectively at opposite sides. As shown in the cross-sectional views in  FIG. 7  and  FIG. 8 , the bottom casing  31  has its inner width wider than an outer width of the battery holder  2  so that a cooling duct  4  may be disposed respectively on opposite sides of the battery holder  2 . The top casing  32  is fabricated by folding a metallic plate into a groove shape that can cover the top surface and the opposite side surfaces of the battery holder  2  and can also dispose the cooling duct  4  on the opposite sides of the battery holder  2 , and then lower edges are secured to the bottom casing  31  by means of set screws  35 . In the battery pack shown in  FIG. 2 , as viewed in this drawing, the end face plate  33  sealing the right end of the outer casing  3  is provided with connection ducts  34  connected to the cooling duct  4  existing between the battery holder  2  and the outer casing  3 . Although not shown, the end face plate sealing the left side of the outer casing  3  in  FIG. 2  seals the aperture defined by the bottom casing  31  and the top casing  32 . 
     In the battery pack shown in  FIG. 7  and  FIG. 8 , as viewed in the drawings, a cooling duct  4 A on an inlet side is disposed on the right side of the battery holder  2 , and a cooling duct  4 B on the outlet side is disposed on the left side of the battery holder  2 . The battery pack is so designed as to cool the battery when a fluid such as air for cooling the battery flows into the battery holder  2  from the cooling duct  4 A on the inlet side and the fluid is exhausted outside from the cooling duct  4 B on the outlet side. The fluid such as air serves to cool the battery when passing through the cooling gap  7  defined between the surface of the cylindrical battery  1  and the opposed wall  12  of the battery holder  2 . The fluid flowing through the cooling gap  7  is air. It should be noted, however, the fluid flowing through the cooling gap  7  can also be a fluid composed of either a gas other than the air or a liquid. An explanation shall be made in detail below, based on the air to be used as the fluid flowing through the cooling gap  7  to cool the battery, but the fluid is not specifically limited to the air. 
     The battery holder  2  includes: the holder main body  10  accommodating the batteries; and the end plate  20  connected to the opposite ends of the holder main body  10 . 
     The holder main body  10  has its entirety integrally formed with a plastic material. As shown in the sectional view in  FIG. 3  and in the perspective view in  FIG. 5 , the holder main body  10  has a plurality of opposed walls  12  disposed in a mutually parallel posture inside the peripheral walls  11  and also has a storage portion  13  disposed for accommodating the plurality of cylindrical batteries  1  between the opposed walls  12 . The holder main body  10  has the cooling gap  7  defined between the opposed wall  12  and the cylindrical battery  1  to cause the air to flow for cooling the battery. Further, the opposed wall  12  is provided, on its opposite faces, with a protrusion  14  projecting toward the swale defined between the adjacent cylindrical batteries  1  to form a thick portion  15 . The protrusion  14  allows an inner surface of the opposed wall  12  to approach the surface of the cylindrical battery  1 , thus narrowing the cooling gap  7  between the battery and the inner surface of the opposed wall  12 . Further, in the holder main body  10  shown in  FIG. 7  and  FIG. 8 , the height of the protrusion  14  projecting toward the swale between the adjacent cylindrical batteries  1  is made larger in the leeward than in the windward. The protrusion  14  projecting high serves to accelerate the velocity of air by narrowing the cooling gap  7  defined around the surface of the battery. Therefore, the battery holder  2  thus structured is capable of uniformly cooling the cylindrical batteries  1  both in the windward and in the leeward. This is because even when the temperature of the fluid such as the air is elevated in the leeward, the fluid is efficiently cooled due to the higher velocity of the air. Particularly, when the protrusion  14  in the leeward is formed to follow along the surface of the cylindrical battery  1 , the air is blown at a high speed for an efficient cooling operation over a wide area of the surface of the cylindrical battery  1  in the leeward. 
     The thick portion  15  of the opposed wall  12  produced by the protrusion  14  has a through hole  16  extending through in the longitudinal direction of the cylindrical battery  1 . Since the illustrated battery holder  2  accommodates the cylindrical batteries  1  in three rows, the opposed wall  12  has two pieces of protrusions  14  on the opposite sides, resultantly with the thick portion  15  being formed in two places. The illustrated opposed wall  12  has the protrusion  14  respectively at the boundary of the cylindrical batteries  1  disposed in the first and second rows and at the boundary of the cylindrical batteries  1  disposed in the second and third rows. The thick portion  15  in the windward is cylindrical, has a through hole  16  inside for insertion of the connection rod  8 , and has the protrusion  14 , with its cross section being shaped to be semicircular, at the opposite sides of the opposed wall  12 . The thick portion  15  in the leeward is larger than the thick portion in the windward, with the surface of the protrusion  14  being shaped to follow along the surface of the cylindrical battery  1 , and has a tube  17  inside for insertion of the connection rod  8 . 
     Further, as shown in the sectional view in  FIG. 3 , the holder main body  10  has an inlet  18  and outlet  19  to allow the fluid such as air for cooling the battery to flow through. The inlet  18  and the outlet  19  are respectively shaped in a slit form extending in the longitudinal direction of the cylindrical battery  1 , and thus the air is blown over the entire cylindrical battery  1 . The inlet  18  is opened on the opposite sides of respective storage portions  13 , while the outlet  19  is opened in the center portion of the respective storage portions  13 . In the holder main body  10 , the air coming in through the inlet  18  disposed on the opposite sides of the respective storage portions  13  passes by the opposite sides of the cylindrical battery  1 , that is, the air is blown from the top to the bottom as viewed in  FIG. 3 , and then goes outside the holder main body  10  through the outlet  19 . Therefore, the battery pack is so designed as to forcibly blow the air, for cooling the battery, in the sequential route of the cooling duct  4 A on the inlet side, the inlet  18 , the cooling gap  7 , the outlet  19 , and the cooling duct  4 B on the outlet side. 
     In the case of the above-described battery pack, since the cylindrical batteries  1  are accommodated in three rows between a pair of opposed walls  12 , the two thick portions  15  are provided, through which the through hole is defined respectively. In the case of a battery pack where the cylindrical batteries are accommodated in two rows between the opposed walls, a single piece of thick portion can be disposed on the opposed wall, through which a through hole is defined. Further, the battery pack of the present invention can be so structured as to accommodate the cylindrical batteries in four or more rows between the pair of opposed walls, having one to three pieces of thick portions in the opposed walls, through which thick portions the through hole is respectively defined so that the connection rod is inserted through the hole to connect the end plates together. 
     The end plate  20  has a fit-on wall  21  integrally formed along the periphery. In the end plate  20 , the peripheral wall  11  of the holder main body  10  is inserted inside the fit-on wall  21  to be connected to a fixed position of the holder main body  10 . Further, the end plate  20  has a fit-on portion  22  to dispose the bus bar  5  in a fixed portion, the bus bar  5  being connected to the terminal electrode  6  of the cylindrical battery  1  accommodated in the holder main body  10 . The end plate  20  shown in  FIG. 6  has a fit-on rib  23  integrally formed along the periphery of the fit-on portion  22 . Extended through the opposite ends of the fit-on portion  22  is a stopper hole  24  for securing the bus bar  5  to the terminal electrode  6  of the cylindrical battery  1 . The stopper hole  24  serves to pass the set screw  28  on to the terminal electrode  6  of the cylindrical battery  1  after extending through the bus bar  5 , and thus the bus bar  5  is secured to the terminal electrode  6 . 
     Further, the end plate  20  has a connection hole  26  defined for insertion of the connection rod  8  which is inserted through the through hole  16  of the holder main body  10 . The end plate  20  shown in  FIG. 6  has a support rib  25  integrally formed also in the periphery of the connection hole  26 , the support rib  25  projecting from the surface. The support rib  25  is equal to the fit-on rib  23  in height, or projects higher than the fit-on rib  23  to contact the inner surface of the outer casing  3 , and thus the outer casing  3  secured to the outside of the end plate  20  is supported from the inner surface. 
     Furthermore, as shown in the sectional view in  FIG. 8 , the end plate  20  has an insertion retainer  27  protruding from the inner surface to retain the battery in a fixed position. The insertion retainer  27  is tubular for the inserted end of the cylindrical battery  1  to be retained in a fixed position; that is to say, the end of the cylindrical battery  1  accommodated in the storage portion  13  of the holder main body  10  is inserted and retained in a fixed position. The cylindrical battery  1  shown in the sectional view in  FIG. 8  has at its opposite ends the terminal electrodes  6  which are narrower than the battery main body, and the terminal electrodes  6  are inserted into the insertion retainer  27  to be disposed in a fixed position. In the cylindrical battery  1  inserted in the storage portion  13 , the terminal electrodes  6  provided at opposite ends are inserted into the insertion retainer  27  of the end plate  20  and disposed in a fixed position of the storage portion  13 . Disposition of the battery in a fixed position in the storage portion  13  is vital to obtain an accurate interval of the cooling gap  7  between the battery and the opposed wall  12 . This is because when the position of the battery is offset toward a radial direction, the cooling gap  7  becomes imbalanced, disabling the battery surface to be uniformly cooled. The cylindrical battery  1  with its opposite ends being inserted into the insertion retainer  27  of the end plate  20  and disposed in a fixed position can be cooled in an ideal state when the cooling gap  7  is accurately defined with respect to the battery surface. 
     Further, the holder main body  10  shown in  FIG. 8  has a retention protrusion  29  formed integrally with the inner surface of the storage portion  13  to retain the inserted cylindrical battery  1  in a fixed position. The illustrated holder main body  10  has the retention protrusion  29  projecting toward the center of the storage portion  13  to retain the center portion of the cylindrical battery  1 . 
     Since the above-described battery holder  2  retains the center portion of the cylindrical battery  1  by means of the holder main body  10  and retains the opposite ends of the battery in a fixed position by means of the end plate  20 , the respective cylindrical battery  1  can be disposed in an accurate position within the battery holder  2 . 
     The end plate  20  shown in  FIG. 4  and  FIG. 6  is divided into a plurality of portions to make each individual length shorter. While the gap  30  produced by such division is adjusted to absorb a dimension error between the end plate  20  and the holder main body  10 , the end plate  20  thus divided into the plurality of portions is secured in an accurate position of the holder main body  10 . In particular, the end plate  20  is secured in an accurate position of the holder main body  10  when the dimension error in the length-wise direction of the elongate end plate  20  is absorbed by the gap  30  produced by the division. Since the end plate  20  and the holder main body  10  are connected via the connection rod  8 , the divided end plate  20  is interconnected in an accurate position via the connection rod  8 . The connection rod  8  is inserted into a connection hole  26  of the end plate  20 , identifies a position relative to the end plate  20 , and is further inserted into the through hole  16  of the holder main body  10  and identifies a position relative to the holder main body  10  to connect the end plate  20  and the holder main body  10  in an accurate position. It should be noted, however, that the battery pack of the present invention may be so structured as not to disassemble the end plate  60  as shown in  FIG. 9  and  FIG. 10 . In these particular drawings, the battery holder is designated by the reference numeral  52 , while the fit-on wall is designated by the reference numeral  61 . 
     The pair of end plates  20  are secured to the holder main body  10  via the connection rod  8 . In the battery pack shown in  FIG. 2  and  FIG. 7 , the end plate  20  is secured to the holder main body  10  by means of the connection rod  8  securing the outer casing  3 . Therefore, the connection rod  8  extends through the outer casing  3 , the end plate  20 , and the holder main body  10 . The illustrated connection rod  8  secures the outer casing  3 , the end plate  20 , and the holder main body  10  by means of a bolt having at its tip an externally threaded screw  8 B, with a nut  9  being screw-threaded on to the externally threaded screw  8 B. The outer casing  3  has an insertion hole  36  defined in the position where the connection rod  8  is inserted. The outer casing  3  shown in  FIG. 3  has a groove  37  defined which extends in the longitudinal direction, with the groove  37  having the insertion hole  36  opened. The outer casing  3  can be so structured that the bolt head  8 A and the nut  9  of the connection rod  8  are guided to the groove  37  in a manner that they do not project from the outer casing  3 . Further, the battery pack shown in  FIG. 2  and  FIG. 3  has a through hole  16  through which a connection rod  8  is not inserted, by disposing in a staggered manner the connection rod  8  which is inserted into the through hole  16 , without inserting the connection rod  8  into every through hole  16  of the holder main body  10 . In the battery pack, when the through hole  16  into which the connection rod  8  is not inserted is connected water-tightly, the battery can be forcibly cooled by causing the cooling medium to flow for cooling the battery. 
     In the battery pack shown in  FIG. 2 , although the end plate  20  is secured to the holder main body  10  by means of the connection rod  8  securing the outer casing  3 , the battery pack can also be so structured that the connection rod is extended through the end plate and the holder main body, that the end plate is secured to the holder main body by means of the connection rod, and that the outer casing is secured to the battery holder by means of another set screw. 
     It should be apparent to those with an ordinary skill in the art that while various preferred embodiments of the invention have been shown and described, it is contemplated that the invention is not limited to the particular embodiments disclosed, which are deemed to be merely illustrative of the inventive concepts and should not be interpreted as limiting the scope of the invention, and which are suitable for all modifications and changes falling within the scope of the invention as defined in the appended claims. The present application is based on Application No. 2008-48,507 filed in Japan on Feb. 28, 2008, the content of which is incorporated herein by reference.