Abstract:
Disclosed herein are a battery module constructed in a structure in which a plurality of plate-shaped secondary battery cells (‘battery cells’), which can be charged and discharged, are sequentially stacked on a lower plate, and an upper plate is coupled to the uppermost battery cell, wherein the plates are provided at the top and bottom and/or the right and left sides thereof with a sliding coupling structure, and the battery module is provided at the front thereof with grips, and a middle- or large-sized battery pack including a plurality of battery modules.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/KR2007/004291, filed Sep. 6, 2007, published in English, which claims the benefit of Korean Patent Application No. 10-2006-0089898, filed Sep. 18, 2006. The disclosures of said applications are incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The present invention relates to a battery module including a sliding coupling structure, and a battery pack including a plurality of battery modules. More particularly, the present invention relates to a battery module constructed in a structure in which a plurality of plate-shaped secondary battery cells (‘battery cells’), which can be charged and discharged, are sequentially stacked on a lower plate, and an upper plate is coupled to the uppermost battery cell, wherein the plates are provided at the top and bottom and/or the right and left sides thereof with a sliding coupling structure, and a middle- or large-sized battery pack including the same. 
     BACKGROUND OF THE INVENTION 
     Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. Also, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuel. 
     Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle- or large-sized devices, such as vehicles, use a middle- or large-sized battery module having a plurality of battery cells electrically connected with each other because high output and large capacity are necessary for the middle- or large-sized devices. 
     Preferably, the middle- or large-sized battery module is manufactured with small size and small weight if possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle- or large-sized battery module. Especially, much interest is currently generated in the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the weight of the pouch-shaped battery is small, the manufacturing costs of the pouch-shaped battery are low, and it is easy to modify the shape of the pouch-shaped battery. 
     For the middle- or large-sized battery module to provide output and capacity required by a predetermined apparatus or device, it is necessary for the middle- or large-sized battery module to be constructed in a structure in which a plurality of battery cells are electrically connected in series with each other, and the battery cells are stable against an external force. 
     Consequently, when a middle- or large-sized battery module is constructed using a plurality of battery cells, a plurality of members for mechanical coupling and electrical connection between the battery cells are generally needed, and, as a result, a process for assembling the mechanical coupling and electrical connection members is very complicated. Furthermore, there is needed a space for coupling, welding, or soldering the mechanical coupling and electrical connection members, with the result that the total size of the system is increased. The increase in size of the system is not preferred in the aspect of the spatial limit of an apparatus or device in which the middle- or large-sized battery module is mounted. Furthermore, the middle- or large-sized battery module must be constructed in a more compact structure in order that the middle- or large-sized battery module is effectively mounted in a limited inner space, such as a vehicle. 
     In addition, when some of the battery modules, constituting the middle- or large-sized battery module, are abnormal, it takes a large amount of time and a large number of processes during the disassembly and assembly of the battery modules to replace the abnormal battery modules with new ones. Also, additional members may be mounted to improve the work efficiency; however, these members may act as a factor increasing the size of the battery module. 
     Consequently, there is a high necessity for a battery module assembly that is more compact, structurally stable, and easily disassembled and assembled, as previously described. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention has been made to solve the above problems, and other technical problems that have yet to be resolved. 
     Specifically, it is an object of the present invention to provide a battery module having a compact structure in which the battery module is stably mounted in a limited space, such as a vehicle, and that is easily assembled and disassembled, thereby improving the work efficiency, and a middle- or large-sized battery pack including the same. 
     In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a battery module constructed in a structure in which a plurality of plate-shaped secondary battery cells (‘battery cells’), which can be charged and discharged, are sequentially stacked on a lower plate, and an upper plate is coupled to the uppermost battery cell, wherein the plates are provided at the top and bottom and/or the right and left sides thereof with a sliding coupling structure. 
     The plates are not particularly restricted so long as the plates are constructed in a structure in which the unit cells are stacked. The plates may be constructed in a case structure (an upper case and a lower case) having a receiving part corresponding to the size of the battery cells such that the battery cells are easily mounted in the receiving part. Preferably, the cases are constructed in a separate structure in which the cases cover the top and bottom of the stacked battery cells, respectively. 
     In a preferred embodiment, the battery module according to the present invention includes a rectangular lower case including an upper end receiving part in which the battery cells are sequentially stacked, a rectangular upper case including a lower end receiving part for covering the battery cells stacked on the lower case, a first circuit unit for electrically connecting the stacked battery cells to each other, the first circuit unit including a sensing board assembly for detecting the voltage and/or current of the battery cells, a second circuit unit electrically connected to the first circuit unit, the second circuit unit including a main board assembly for controlling the overall operation of the battery module, and a third circuit unit electrically connected to the second circuit unit, the third circuit unit being connected to an external output terminal while preventing the overcurrent. 
     The battery module according to the present invention is constructed generally in a compact structure. Specifically, the width of the completed battery module is almost equal to or slightly greater than that of each unit cell. The length of the battery module is greater, by the widths of the first circuit unit and the third circuit unit, than that of each unit cell. The thickness of the battery module is the sum of the thickness of the stacked unit cells, the thickness of the second circuit unit, and the thicknesses of the upper and lower cases. Consequently, the battery module according to the present invention has a size less than that of any conventional battery modules, and therefore, the battery module according to the present invention is effectively mounted in an external apparatus or device to which the battery module according to the present invention will be applied. 
     Each unit cell is not particularly restricted so long as the unit cell is a secondary battery that can be charged and discharged. For example, a lithium secondary battery, a nickel-metal hydride (Ni-MH) battery, a nickel-cadmium (Ni—Cd) battery may be used as the unit cell. Among them, the lithium secondary battery is preferably used as the unit cell because the lithium secondary battery exhibits a high output to weight ratio. Based on its shape, the lithium secondary battery may be classified as a cylindrical battery, a prismatic battery, or a pouch-shaped battery. Among them, the prismatic battery or the pouch-shaped battery are preferably used as the unit cell because the prismatic battery or the pouch-shaped battery can be stacked with high integration. More preferably, the pouch-shaped battery is used as the unit cell because the weight of the pouch-shaped battery is very small. 
     In the battery module according to the present invention, the upper case and the lower case are separated from each other. Consequently, when the capacity and output of the battery module need to be changed according to circumstances, it is possible to add or remove the unit cells between the upper case and the lower case, and therefore, the flexible design of the battery module is accomplished. 
     The overall size of the upper case and the lower case is approximately equivalent to that of each unit cell. Consequently, the upper end receiving part of the lower case and the lower end receiving part of the upper case, in which the unit cells are received, correspond to the size of the cell body of each unit cell. 
     The first circuit unit is mounted to the front of the battery module adjacent to electrode terminals of the unit cells. The first circuit unit includes connection terminals for connecting the unit cells in parallel or series with each other, the sensing board assembly of the first circuit unit receives voltage and current signals from the respective unit cells and detects the temperature of the battery. The temperature of the battery may be measured by the sensing board assembly as the overall temperature of the battery module or the temperatures of the respective unit cells. 
     The construction of the connection members is not particularly restricted so long as the unit cells are connected in parallel or series with each other by the connection members. Preferably, a safety element, for interrupting current when overcurrent or overheat is generated, is connected between the connection members. The safety element may be, for example, a fuse, a bimetal, or a positive temperature coefficient (PTC) element. 
     Preferably, the sensing board assembly is made of a printed circuit board (PCB), and the sensing board assembly is electrically connected to the respective unit cells. 
     The unit cells are electrically connected to the second circuit unit, which is mounted at the lower end receiving part of the upper case, via the first circuit unit. The operation of the battery module is controlled by the main board assembly of the second circuit unit. 
     The third circuit unit, which is electrically connected to the second circuit unit, is mounted to the other side opposite to the side of the battery module where the first circuit unit is mounted. The third circuit unit is the final element of the battery module, which is connected to an external device for controlling the overcharge, overdischarge, and overcurrent of the unit cells. The control of the overcharge, overdischarge, and overcurrent of the unit cells may be performed by a switching element included in the third circuit unit. 
     Preferably, the main board assembly is made of a PCB. Consequently, the main board assembly of the second circuit unit has a specific strength sufficient to protect the unit cells against the external impacts. According to circumstances, therefore, a safety member, including the second circuit unit, may be mounted only to the upper case. 
     The battery module is constructed in a structure in which the circuit units for controlling the operation of the unit cells are connected to each other such that the circuit units surround the battery module. Consequently, the overall size of the battery module is greatly reduced. 
     The third circuit unit includes a switching element for controlling the overcurrent during the charge and discharge of the battery cells, and the third circuit unit is mounted at the rear of the battery module opposite to electrode terminals of the battery cells. 
     The switching element is connected in series, to the unit cells, constituting the battery module, for controlling the current flowing in the unit cells. The switching element is connected to a protection circuit for detecting the voltage and/or the current of the unit cells to control the switching element. The switching element is not particularly restricted so long as the switching element controls overcharge, overdischarge, and overcurrent of the unit cells. For example, an FET element or a transistor may be used as the switching element. Preferably, the FET element is used as the switching element. 
     The switching element is connected to a control circuit for detecting the voltage and/or the current of the unit cells to control the switching element. The switching element is controlled on or off according to a signal outputted from the control circuit. 
     The module case has a sliding coupling structure. The sliding coupling structure includes sliding grooves formed at the top of the upper case in the longitudinal direction of the upper case and corresponding sliding protrusions formed at the bottom of the lower case in the longitudinal direction of the lower case. Consequently, when two or more battery modules are stacked in the height direction, the sliding protrusions formed at the bottom of the upper battery module are located in the corresponding sliding grooves formed at the top of the lower battery module, and then the upper battery module is slid in the longitudinal direction, with the result that the mechanical coupling between the battery modules is accomplished through the sliding coupling structure without using additional connection members. 
     The sliding coupling structure may be constructed in various constructions, preferred examples of which will be described below. 
     The sliding grooves may be formed at the right and left sides of the top of the upper case, and the sliding protrusions may be formed at the right and left sides of the bottom of the lower case, to maximize the coupling force of the sliding coupling structure. Especially, the sliding grooves and the sliding protrusions are preferably constructed in a linear motion (LM) rail and block structure. 
     The front end of each sliding groove may have a width larger than that of the corresponding sliding protrusion, such that the assembly position error is allowed during the coupling, whereby the assembly efficiency and speed are improved. Also, the front end of each sliding groove may be formed at a relatively high height such that the coupling is stably and securely maintained. 
     Each sliding groove is provided at the rear end thereof with a stopping wall for stopping further movement of the corresponding sliding protrusion after the sliding protrusions are completely engaged in the corresponding sliding grooves during the coupling between the battery modules, thereby accomplishing the correct coupling between the battery modules at a predetermined position. 
     Also, the battery module case is provided at the front thereof with depressed grips, by which the assembly and disassembly of the battery modules are easily performed. Preferably, the lower case is provided at the front thereof with depressed grips. 
     In accordance with another aspect of the present invention, there is provided a middle- or large-sized battery pack having a high output and large capacity, which includes a plurality of battery modules. 
     The middle- or large-sized battery pack according to the present invention may be used in various applications. For example, the middle- or large-sized battery pack according to the present invention may be used as a power source for vehicles, such as electric bicycles (E-bike), electric motorcycles, electric vehicles, and hybrid electric vehicles, or a power source for various applications and products, including industrial or domestic apparatuses. The middle- or large-sized battery pack according to the present invention is constructed in a compact structure and in a structure in which the assembly and disassembly of the battery pack is easily performed to obtain a desired capacity of the battery pack. Consequently, the middle- or large-sized battery pack according to the present invention is preferably used as a charging and discharging power source for electric vehicles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIGS. 1 and 2  are perspective views illustrating the top and bottom of a battery module according to a preferred embodiment of the present invention, respectively; 
         FIG. 3  is a perspective view illustrating the rear of the battery module according to the preferred embodiment of the present invention; 
         FIGS. 4 and 5  are typical views illustrating a process for stacking a plurality of battery modules in the height direction; and 
         FIGS. 6 and 7  are typical views illustrating a process for stacking a plurality of battery modules not only in the height direction but also in the lateral direction. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted, however, that the scope of the present invention is not limited by the illustrated embodiments. 
       FIG. 1  is a perspective view typically illustrating a battery module according to a preferred embodiment of the present invention. 
     Referring to  FIG. 1 , the battery module  100  includes an upper case  110 , a lower case  120 , a plurality of unit cells  200 , a first circuit unit  300 , a second circuit unit  400 , and a third circuit unit  500 . The unit cells  200  are stacked between the upper case  110  and the lower case  120 , which are separated from each other. The first circuit unit  300  is located at the front of the battery module  100 , the second circuit unit  400  is located at the bottom of the battery module  100 , and the third circuit unit  500  is located at the rear of the battery module  100 . 
     Since the upper case  110  and the lower case  120  are separated from each other, the number of the unit cells  200 , which are stackable, is not limited by the upper case  110  or the lower case  120 . Consequently, it is possible to easily design the battery module  100 , such that the battery module  100  has a desired electrical capacity and output, by modifying the first circuit unit  300  and the third circuit unit  500  depending upon the number of the stacked unit cells  200 . Also, the unit cells  200  are exposed to the outside, and therefore, heat dissipation is efficiently accomplished during the charge and discharge of the unit cells  200 . 
     The first circuit unit  300  is mounted to one side of the battery module  100  adjacent to electrode terminals of the unit cells  200 . The first circuit unit  300  includes a sensing board assembly for connecting the unit cells  200  in parallel or series with each other and detecting the voltages of the respective unit cells  200  according to the present invention. 
     The unit cells  200  are electrically connected to the second circuit unit  400 , which is mounted at the top of the upper case  110 , via the first circuit unit  300 . The operation of the battery module  100  is controlled by a main board assembly of the second circuit unit  400 . 
     The third circuit unit  500 , which is electrically connected to the second circuit unit  400 , is mounted to the other side opposite to the side of the battery module where the first circuit unit  300  is mounted. The third circuit unit  500  is the final element of the battery module  100 , which is connected to an external device (not shown) for controlling the overcharge, overdischarge, and overcurrent of the unit cells. The control of the overcharge, overdischarge, and overcurrent of the unit cells may be performed by a switching element (not shown), such as a field effect transistor (FET), included in the third circuit unit  500 . 
     At the top of the upper case  110  are formed sliding grooves  111 , which extend along opposite sides of the upper case  110  in the longitudinal direction of the upper case  110 . The front end  112  of each sliding groove  111  has a width larger than that of a corresponding sliding protrusion (not shown). Also, the front end  112  of each sliding groove  111  is formed at a relatively high height such that the coupling is stably and securely maintained. 
     At the rear end of each sliding groove  111  is formed a stopping wall  113  for stopping further movement of the corresponding sliding protrusion. Consequently, when two or more battery modules  100  are stacked, it is possible to stably couple the battery modules at a correct position. 
     Also, the battery module  100  is provided at opposite sides of the front thereof with depressed grips  130 , which improves the work efficiency during the assembly and disassembly of the battery module  100 . 
       FIG. 2  is a perspective view illustrating the bottom of the battery module shown in  FIG. 1 . 
     Referring to  FIG. 2 , the lower case  120  of the battery module is provided at the bottom thereof with sliding protrusions  121 , which extend along opposite sides of the lower case  120  in the longitudinal direction of the lower case  120 . At the front of the lower case  120  are formed depressed grips  130 . The sliding protrusions  121  are engaged in the corresponding sliding grooves (not shown), which are formed at the top of the upper case  110 , whereby the mechanical coupling between the battery modules is accomplished. 
     Also, the battery module  100  is provided at the front thereof with various connectors and other members, including a switching board and a heat dissipation structure, which will be described below in more detail with reference to  FIG. 3 . 
       FIG. 3  is a perspective view illustrating the rear of the battery module shown in  FIG. 1 . 
     Referring to  FIG. 3 , the switching board is constructed in a structure in which a rectangular heat dissipation structure  540  is mounted on a printed circuit board (PCB)  510  while the heat dissipation structure  540  is connected to six FET elements  550 , which are switching elements. 
     The heat dissipation structure  540  is constructed in a structure in which the FET elements  550  are coupled to opposite side frames of the heat dissipation structure  540 , and a plurality of heat dissipation ribs protrude upward from a main frame integrally connected to the side frames. 
     At the left side of the heat dissipation structure  540  is formed a connector supporting member  520 , which extends in the longitudinal direction of the battery module  100 . On the connector supporting member  520  are mounted a communication connector  531  and a power connector  532 , through which the battery module  100  is electrically connected to an external circuit. 
       FIGS. 4 and 5  are typical views illustrating a process for stacking two battery modules according to the present invention in the height direction. 
     Referring first to  FIG. 4 , the sliding grooves  111  are formed at the top of the module case such that the sliding grooves  111  extend in the longitudinal direction of the module case, and the sliding protrusions (not shown) corresponding to the sliding grooves  111  are formed at the bottom of the module case. Consequently, the two battery modules are coupled in the height direction by the engagement between the sliding grooves  111  and the corresponding sliding protrusions. Specifically, when the battery modules are stacked in the height direction, the sliding protrusions formed at the bottom of the upper battery module  110   b  are located in the corresponding sliding grooves formed at the top of the lower battery module  110   a , and then the upper battery module  110   b  is slid in the longitudinal direction until the sliding protrusions of the upper battery module  110   b  reach the stopping walls  113  of the lower battery module  110   a . Consequently, the mechanical coupling  600  between the two battery modules is accomplished through the sliding coupling structure without using additional connection members.  FIG. 5  illustrates the mechanical coupling  600  between the two battery modules while the two battery modules are stacked in the height direction. 
       FIGS. 6 and 7  are typical views illustrating a process for stacking a plurality of battery modules not only in the height direction but also in the lateral direction. 
     First, as shown in  FIGS. 4 and 5 , battery modules  100   a  and  100   b  are stacked in the height direction by the coupling between the battery modules  100   a  and  100   b , and then, as shown in  FIGS. 6 and 7 , battery modules  100   c  and  100   d  are stacked in the height direction by the coupling between the battery modules  100   c  and  100   d  at one side of the stacked battery module assembly in the same manner. The battery modules  100   c  and  100   d  may be coupled to the battery modules  100   a  and  100   b , or may be in tight contact with the battery modules  100   a  and  100   b  while the battery modules  100   c  and  100   d  are separated from the battery modules  100   a  and  100   b . In the former structure, it is necessary to form the sliding grooves and the corresponding sliding protrusions at the right and left sides as well as the top and bottom of the battery modules  100   a ,  100   b ,  100   c , and  100   d . However, when the battery modules  100   a ,  100   b ,  100   c , and  100   d  have sliding coupling structures at the sides thereof, a precise positional control is required to couple the battery modules  100   a ,  100   b ,  100   c , and  100   d  in correct positions. For this reason, it is preferable to use the latter structure in which the battery modules  100   c  and  100   d  are in tight contact with the battery modules  100   a  and  100   b  while the battery modules  100   c  and  100   d  are separated from the battery modules  100   a  and  100   b.    
     The assembly and disassembly of the battery modules  100   a ,  100   b ,  100   c , and  100   d  are easily performed using grips  130  formed at the opposite sides of the front of each battery modules. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 
     INDUSTRIAL APPLICABILITY 
     As apparent from the above description, the battery module according to the present invention is constructed in a compact structure and is structurally stable. Also, the mechanical coupling and the electrical connection between the battery modules are accomplished by the sliding coupling between the battery modules, with the result that additional members for the mechanical coupling and the electrical connection between the battery modules are not needed, and therefore, the battery module is effectively mounted in a limited inner space, such as a vehicle. Furthermore, the disassembly and assembly of the battery module are easily performed using the grips formed at the front of the battery module.