Battery pack

A battery pack includes a module stack body having a plurality of stacked battery modules; first and second connecting members each provided on the same surface of the module stack body in order to hold the stacked battery modules and extending in the stacking direction of the battery modules; a first reinforcing member fixed to the first and second connecting members at first and second fixed points; and a second reinforcing member fixed to the first and second connecting members at third and fourth fixed points. Orientation of the components along the stacking direction of the battery modules of vectors having respectively the first and third fixed points as a start point and the second and fourth fixed points as an end point are opposed to each other.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Japanese Patent Application No. 2012-204139, filed Sep. 18, 2012, incorporated herein in its entirety.

TECHNICAL FIELD

The present invention relates to an assembled battery or a battery pack constructed by stacking a plurality of battery modules.

BACKGROUND

A technique for fixing a plurality of stacked battery cells by tie bars or bands is known (see, for example, Japanese Patent Application Publication No. 2012-18915 A). In Japanese Patent Application Publication No. 2012-18915 A, although the plurality of battery cells stacked can be effectively suppressed from being deformed by expansion of the battery cells or the like, when external force is applied along the stacking direction of the battery cells, there is a problem that the plurality of battery cells of the battery cell may sometimes be tilted in a chain reaction triggered by the battery cell receiving the external force.

SUMMARY

The object to be attained by the present invention is to provide an assembled battery or a battery pack that is held stably even if the external force is applied along the stacking direction of the battery cells.

The battery pack according to the present invention is provided with a first connecting member, a second connecting member, a first reinforcing member fixed to the first and second connecting members at a first fixed point and a second fixed point, respectively, and a second reinforcing member fixed to the first and second connecting members at a third fixed point and a fourth fixed point, respectively.

Further, by setting the direction of a component along the stacking direction of the battery modules in a first vector having the first fixed point as a start point and the second fixed point as end point and the direction of a component along the stacking direction of the battery modules in a second vector having the third fixed point as a start point and the fourth fixed point as end point opposite to each other, the problem described above is solved.

According to the present invention, when an external force is applied to the battery pack along the stacking direction of the battery modules, one of the first and second reinforcing members is disposed to be inclined so as to counteract the external force. Therefore, it is possible for the stacked battery modules to be suppressed from being tilted by the external force.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A description will be given below of embodiments according to the present invention with reference to the drawings.

First Embodiment

FIG. 1is a front view showing the battery pack1in this embodiment,FIG. 2shows an exploded perspective view of a battery module2in the present embodiment,FIG. 3is a partial exploded perspective view showing the battery pack1, and finally,FIGS. 4 to 6are front views respectively showing a first to a third modifications of the reinforcing members51and52in the instant embodiment.

A battery pack1according to the instant embodiment, as shown inFIG. 1, is provided with a module stack body20, a first and a second end plates31,32respectively provided on the left and right sides of the module stack body20in the figure, a first and second connecting members41,42fixedly connecting the first and second end plates31,32, and a first and second reinforcing members51,52reinforcing the assembled battery pack1by connecting the first and second connecting members41,42.

The module stack body20, as shown inFIG. 1, is a laminate body composed of a plurality of battery modules2stacked in a row in the X direction inFIG. 1. Note that each of the battery modules2is fixedly connected to each other by through bolts (not shown).

The module stack body20in the instant embodiment thereby constitutes a battery pack1using seven battery modules2. However, the number of battery modules2that form the battery pack1is not particularly limited. In the following, these seven cell modules2are also referred to as a battery module2A, a battery module2B, a battery module2C, a battery module2D, a battery modules2E, a battery module2F, and a battery modules2G, respectively.

The battery module2, as shown inFIG. 2, is provided with a plurality of single or unit cells21stacked on each other, a spacer22interposed between the unit cells21, a case23that accommodate these single cells21and the spacers22.

The unit cell21is, for example, a laminate battery such as a lithium ion secondary battery. The unit cell21, though not specifically shown, is provided with a laminated body formed by alternately stacking a positive electrode plate and a negative electrode plate with a separator interposed there between, and a laminate film for sealing the laminated body with electrolyte solution. A positive electrode tab connected to the positive electrode plate is derived from one end of the laminate film while the negative electrode tab connected to the negative electrode plate is derived from the opposite end of the laminate film. Note that the unit cell21may be composed of a nickel hydrogen battery, or lead battery or the like.

In the instant embodiment, after stacking the adjacent unit cells21with the direction of a positive electrode tab and that of a negative electrode tab alternated, by connecting directly the positive electrode tab and the negative electrode tab between the adjacent unit cells21, each unit cell21will be joined in series. Further, the plurality of connected unit cells is electrically connected at its one end to a positive electrode side and negative electrode side output terminals24,25. Note that the electrical connection of the cells21is not particularly limited thereto.

Such plurality of unit cells21, as shown inFIG. 2, are housed in the case23in a state in which spacers22are interposed for keeping the insulation of the unit cell21adjacent to each other.

The case23is composed of a lower case231having a box shape and an upper case232of lid shape. These lower and upper cases231,232are formed, for example, of an aluminum plate.

In the instant embodiment, eight unit cells21are stacked and housed in the case23. However, the number of cells21to be stacked is not particularly limited. For example, a single cell21may be contained in the case23. The structure of the case is not particularly limited to the one described above, and the lower case and upper case, may be both formed in box shape and structured to meet both openings.

On the side on which the positive electrode and the negative terminals24and25are derived in an outer surface of the upper case232, as shown inFIG. 2, a bolt support member26is attached. A bolt261provided on the bolt support member26is used when fixedly fastening the first and second connecting members41,42and the first and second reinforcing members51,52by a nut27.

The plurality of battery modules2in the instant embodiment, as shown inFIG. 1, the positive terminal24and the negative terminal25of adjacent battery modules2are laminated so as to be alternately arranged, respectively. That is, the plurality of battery modules2is laminated by reversing the direction alternately.

Further, when using the battery pack1, in order for all the plurality of battery modules to be connected in series, the positive electrode terminal24and the negative electrode tab of adjacent battery modules2are connected one after another by a connecting member (not shown). Note that the electrical connection relationship between the battery modules is not limited thereto.

The first and second end plates31and32, as shown inFIG. 3, have a generally the same area as the side face of the battery module2and are plate-like member having a cross-sectional shape of the U formed from a steel such as iron. These two end plates31and32, as shown inFIGS. 1 and 3, are provided so as to sandwich from both sides of the stacking direction of the battery modules2provided so as to sandwich the module stack body20from both sides thereof in the stacking direction of the battery modules2. The first end plate31is arranged on the left end of theFIG. 1while the second end plate32is placed on the right end in theFIG. 1.

On the upper and lower ends of the first and second end plates31and32, as shown inFIG. 3, through holes341and342are formed, respectively. The lower through hole341may receive a bolt33for insertion, which is used for fixing to the first connecting member41described below. Also, the upper through hole342may receive a bold33for insertion, which is used for fixing to the second connecting member.

The first and second connecting members41and42are a flat bar-like member provided along the stacking direction of the battery modules2and are connected to first and second end plates31and32described above, respectively. The first and second connecting members41and42are dimensioned to have approximately the same length of the battery module2of the module stack body20in the stacking direction, and are formed from steel such as iron. In the instant embodiment, the first connecting member41is arranged on the lower side inFIG. 1while the second connecting member42is disposed on the upper side inFIG. 1.

The first connecting member41, as shown inFIG. 3, is formed with through holes431at both ends in the stacking direction of battery modules2, and a plurality of through holes (seven in this example)441are formed substantially equally spaced between the through holes431at the both ends7. The plurality of through holes441are arranged to so as to correspond to the positions of the bolts261provided on each battery module2A to2G.

Both ends of the first connecting member41are fixed to the lower ends of the first and second end plates31and32using bolts33and nuts28.

Specifically, after inserting the bolt33into the through hole431at one end of the first connecting member41and the through hole341of the first end plate31, by fastening the bolt33and a nut28with the first connecting member41and the first end plate31being sandwiched, the first connecting member41is fixed to the first end plate31at its lower end.

Similarly, after inserting the bolt33into the through hole431at the other end of the first connecting member41and the through hole341of the second end plate32, by fastening the bolt33and a nut28with the first connecting member41and the second end plate32being sandwiched, the first connecting member41is fixed to the lower end of the second end plate32.

Also, the first connecting member41is connected by bolts261and nuts27of the battery modules2A to2G and fixed respectively to the battery module2A to2G.

Specifically, as shown inFIG. 3, after inserting into the through holes441of the first connecting member41bolts261respectively formed on the battery modules2A to2G, by fastening the bolts261and nuts27with the first connecting member41sandwiched, the first connecting member41is fixed to the battery modules2A to2G. Note that, with respect to the fixing portions of the reinforcing members51,52, after inserting a bolt261into the through hole441of the first connecting member41and through hole541of the reinforcing members51,52, fastening takes place.

The second connecting member42, as shown inFIG. 3, is formed with through holes432at both ends in the stacking direction of battery modules2, and a plurality of through holes (seven in this example)442are formed substantially equally spaced between the through holes432at the both ends7. The plurality of through holes442are arranged to so as to correspond to the positions of the bolts261provided on each battery module2A to2G.

Further, both ends of the second connecting member42are fixed to the upper ends of the first and second end plates31and32using bolts33and nuts28.

Specifically, after inserting the bolt33into the through hole432at one end of the second connecting member42and the through hole342of the first end plate31, by fastening the bolt33and a nut28with the second connecting member42and the first end plate31being sandwiched, the second connecting member42is fixed to the first end plate31at its upper end.

Similarly, after inserting the bolt33into the through hole432at the other end of the second connecting member42and the through hole342of the second end plate32, by fastening the bolt33and a nut28with the second connecting member42and the second end plate32being sandwiched, the second connecting member42is fixed to the upper end of the second end plate32.

Also, the second connecting member42is connected by bolts261and nuts27of the battery modules2A to2G and fixed respectively to the battery module2A to2G.

Specifically, as shown inFIG. 3, after inserting into the through holes442of the second connecting member42bolts261respectively formed on the battery modules2A to2G, by fastening the bolts261and nuts27with the second connecting member42sandwiched, the second connecting member42is fixed to the battery modules2A to2G. Note that, with respect to the fixing portions of the reinforcing members51,52, after inserting a bolt261into the through hole442of the second connecting member42and the through hole542of the reinforcing members51,52, fastening takes place.

Note that if the battery modules2A,2G arranged on both ends of the plurality of the battery modules2each has at least one bolt261for being fixed to the first and second connecting members41,42, the first and second end plates may be omitted. The number of the battery modules2fixed to the first and second connecting members41,42is not particularly limited. For example, all the battery modules2A to2G may be fixed to the first and second connecting members41and42, or alternatively, every other battery modules2may be fixed to the first and second connecting members41and42.

Also, when the first and second connecting members41,42are connected to the first and second end plates31,32respectively, the bolt261associated with battery modules2A to2G may be omitted.

The first and second reinforcing members51and52, as shown inFIG. 1, are intended for connecting the first connecting member41and the second connecting member42, and are formed from steel such as iron shaped in a flat plate.

The upper and lower ends of the first and second reinforcing members51and52, as shown inFIG. 3, are provided with through holes541,542for insertion of the bolts261provided on the battery modules2, and, by using the bolt261, the first and second reinforcing members51and52are fixed to the first and second connecting members41,42, respectively.

Specifically, as shown inFIG. 3, after the bolt261of the battery module2is inserted into a lower side through hole541of the first and second reinforcing members51,52as well as the through hole441of the first connecting member41, by fastening the bolt261and the nut27, the first and second reinforcing members51,52are respectively fixed to the first connecting member41.

Similarly, after the bolt261of the battery module2is inserted into a upper side through hole542of the first and second reinforcing members51,52as well as the through hole442of the second connecting member42, by fastening the bolt261and the nut27, the first and second reinforcing members51,52are respectively fixed to the second connecting member42.

Though not shown, the first and second connecting members41,42as well as the first and second reinforcing members51and52as described above are also provided on the back side of the module stack body20.

In the instant embodiment, by using the bolt261provided on the battery module2, the first and second reinforcing members51and52are fixed to the first and second connecting members41and42. However, the structure is not particularly limited thereto. For example, using a bolt separate from the battery module2, the first and second reinforcing members51and52may be fixed to the first and second connecting members41,42.

In the instant embodiment, as shown inFIG. 1, the lower end of the first reinforcing member51(the first fixed point P1) is fixed by the bolt261provided on the battery module2C while the upper end (second fixed point P2) of the first reinforcing member51is fixed by the bolt261provided on the battery module2B. On the other hand, the lower end of the second reinforcing member52(the third fixed point P3) is fixed by the bolt261provided on the battery module2E while the upper end (second fixed point P2) of the second reinforcing member52is fixed by the bolt261provided on the battery module2F.

Thus, the first reinforcing member51and the second reinforcing member52are mounted so as to be separated from each other in the upward direction inFIG. 1. That is, the orientation of the X direction component (hereinafter referred to as the vector Va.) of a vector (hereinafter referred to as the vector VA) directing from the first fixed point P1toward the second fixed point P2and the orientation of the X direction component (hereinafter, referred to as a vector Vb.) of a vector directing from the third fixed point P3toward the fourth fixed point P4(hereinafter referred to as the vector VB) are opposite to each other.

Note that, as long as the direction of the vector Va and the direction of the vector Vb are configured to be opposite to each other, the configuration is not limited to that described above. Note that the length of the first and second reinforcing members51,52may be appropriately adjusted depending on the fixed positions of the upper and lower ends.

For example, the first reinforcing member51is fixed by the bolts261of adjacent battery modules2B,2C. However, by using the bolt261of the battery module2B and the bolt261of the battery module2D, the first reinforcing member51is fixed across the battery module2C. Similarly, the first reinforcing member51may be fixed across more than two battery modules2. At this time, the second reinforcing member52may be fixed across one or more battery modules2.

Further, in the instant embodiment, the first and second reinforcing members51and52are mounted so as to separate from each other upwardly inFIG. 1. The construction is not limited thereto. For example, the first and second reinforcing members51and52may be attached so as to be oriented away from each other downward in theFIG. 1.

Further, as shown inFIG. 4, the first reinforcing member51may be of a substantially triangular shape and fixed to the first and second connecting members41,42by a total of three fixed portions, i.e., by two bolts provided on the battery module2B and one of the bolts261provided on the battery module2C. Further, the second reinforcing member52may also be of a substantially triangular shape and may be fixed to the first and second connecting members41,42by a total of three fixed portions, i.e., by one of the bolts261provided on the battery module2E and two bolts261provided on the battery module2F.

Similarly, at least one of the first and second reinforcing members51and52may be fixed to the first and second connecting members41,42in four or more fixed points.

Now, a description is given of the operation of the instant embodiment.

In the instant embodiment, two connecting members41and42are provided to secure two end plates31and32located at both ends of the plurality of stacked battery modules2A to2G. Further, first and second reinforcing members are provided to connect these two connecting members41,42to thereby for reinforcing the assembled battery pack1.

As shown inFIG. 1, with respect to these two reinforcing members51and52, the direction or orientation of the component vector Va along the X direction in the vector VA and the direction of the component vector Vb along the X direction in the vector VB are opposite to each other. Therefore, even when an external force along the stacking direction of the battery modules2A to2G in the assembled battery pack1is applied, it is possible to prevent the plurality of battery modules2from being tilted.

That is, for example, when an external force F is applied to the upper left position in the stacking direction of the battery modules2A to2G of the battery stack1inFIG. 1(arrow F in the figure), the first reinforcing member51, against the direction of the external force F, exhibits a counter-acting vector Va. Thus, the external force F is cancelled by the presence of the first reinforcing member51. Therefore, the battery module2A is prevented from being tilted due to the external force. Consequently, the chain reaction will be prevented from occurring in which multiple battery modules2B to2G will also be subject to tilting in response thereto. Therefore, it is possible to stably hold the battery modules2A to2G.

Further, in the instant embodiment, by using the bolts261attached to the battery modules2A to2G, the first and second connecting members41,42and the first and second reinforcing members51and52are connected to each other. Accordingly, since the battery modules2A to2G are fixed directly with the connecting members41,42and the reinforcing members51and52, it is possible to hold the battery modules2A to2G more stably.

As shown inFIG. 5, by fixedly fastening one of the upper or lower ends of the first reinforcing member51and the one of the upper or lower ends of the second reinforcing member52at the same position (by the bolt attached to the battery module2D) jointly, the first and second reinforcing members51,52may be fixed to the first and second connecting members41,42at a total of three fixed portions.

In this case, even when the number of battery modules2of the battery pack1is small, since it is possible to efficiently secure the vector Va of the first reinforcing member51and the vector Vb of the second reinforcing member52, the battery modules2will be prevented from tilting due to an external force so that the battery modules2A to2G may be held stably.

Also, as shown inFIG. 6, the first and second reinforcing members51and52may be formed of a single or integral reinforcing member53.

In this case, it is possible to reduce the number of components that form the assembled battery pack1. Further, it is possible to improve workability in assembling the battery pack1.

Even at the smaller number of battery modules2of the battery pack1, since it is possible to secure the vector Va and the vector Vb efficiently by the reinforcing member53, the battery modules2are prevented from tilting by an external force so that the battery modules2A to2G can be stably maintained.

The direction of the vector Va in the instant embodiment corresponds to an example of the direction of a component along the stacking direction of the battery modules in a first vector having the first fixed point as a start point and the second fixed point as end point according to the present invention whereas the direction of the vector Vb in the instant embodiment corresponds to an example of the direction of a component along the stacking direction of the battery modules in a second vector having the third fixed point as a start point and the fourth fixed point as end point according to the present invention.

Second Embodiment

FIG. 7is a front view showing a battery pack1B of the instant embodiment,FIG. 8is a front view showing a modification of the reinforcing member51B,52B in the instant embodiment. Except that the battery pack1B of the second embodiment does not have a second connecting member42and the upper ends of the first and second reinforcing members51B,52B are fixed to either the first or second end plate, the construction is similar to that of the first embodiment described above. Therefore, a description is given only of the portion different from the first embodiment, and the same portion as the first embodiment is attached the same reference numeral with the corresponding description omitted.

The first and second reinforcing members51B,52B serves as, as shown inFIG. 7, members for connecting the first connecting member41and the first or second end plate31and32, and are flat-shaped flat and formed from steel such as iron.

Though not shown specifically, the first and second reinforcing member51B,52B are respectively formed at the upper end with a through hole for insertion of the bolt33for connecting to the end plates31,32, and at the lower end with a through hole for insertion of the bolt261provided on the battery module2.

The upper ends of the first and second reinforcing member51B,52B are fixed to the upper ends of the end plates31,32, respectively using bolts33and nuts28.

Specifically, after inserting the bolt33into the through hole at one end of the first reinforcing member51B and the through hole342of the first end plate31, by fastening the bolt33and a nut28with the first reinforcing member51B and the first end plate31being sandwiched, the first reinforcing member51B is fixed to the first end plate31at its upper end.

Similarly, after inserting the bolt33into the through hole431at the upper end of the second connecting member52B and the through hole342of the second end plate32, by fastening the bolt33and a nut28with the second reinforcing member52B and the second end plate32being sandwiched, the second reinforcing member52B and the upper end of the second end plate32.

The first and second reinforcing members51B are fixed at respective lower end to the first connecting member41using the bolts to the first connecting member261.

Specifically, after inserting a bolt261provided on the battery module2in the respective through hole provided at the lower ends of the first and second reinforcing members51B,52B in alignment with the through hole441of the first connecting member41, and by securing the bolt261and a nut27, the first and second reinforcing members51B,52B are fixed to the first connecting member41, respectively.

Though not shown specifically, the first connecting member41as well as the first and second reinforcing members51B,52B are also provided on the back side of the module stack body20.

In the instant embodiment, as shown inFIG. 7, the lower end of the first reinforcing member51B (first fixing point P1a) is fixed by the bolt261provided on the battery module2B. Further, the second reinforcing member52B is fixed by the bolt261at the lower end (third fixed point P3) using the bolt261provided on the battery module2F.

Further, as described above, the upper end (second fixed point P2) is fixed to the upper end of the first end plate31. In addition, the upper end of the second reinforcing member52B (fourth fixed point P4) of the second reinforcing member52B is fixed to the upper end of the second end plate32. Thus, in the instant embodiment as well, the orientation of the X direction component Va. of a vector VA directing from the first fixed point P1toward the second fixed point P2and the orientation of the X direction component Vb of a vector VB directing from the third fixed point P3toward the fourth fixed point P4are opposite to each other.

Therefore, even when an external force along the stacking direction of the battery modules2A to2G in the assembled battery pack1B is applied, it is possible to prevent the plurality of battery modules2from being tilted and to stably hold the battery modules2A to2G.

Further, as shown inFIG. 7, in the front of the battery pack1B in the instant embodiment, the first and second end plates31,32are connected by using only the first connecting member41. Therefore, it is possible to reduce the number of components constituting the battery pack.1B. In addition it is possible to achieve improved workability during assembly of the battery pack1B while reducing the weight of the battery pack1B.

Further, in the instant embodiment, by using bolts261attached to the battery module2A to2G, the first connecting member41and the first reinforcing members51B,52B are connected to each other. Thus, since the battery modules2A to2G are fixed directly to the reinforcing member51B,52B, it is possible to hold more stably the battery modules2A to2G.

As shown inFIG. 8, by co-fastening the lower end of the reinforcing member51B and the lower end of the reinforcing member52B at the same position (i.e. at the position of the bolt261attached to the battery module2D in the example), the first and second reinforcing members51B,52B may be fixed to the first connecting member41, and the first and second end plates31,32at a total of three fixed portions.

In this case, even when the number of battery modules2of the battery pack1B is small, since it is possible to ensure the vector Va in the first reinforcing member51B and the vector Vb in the second reinforcing member52B efficiently, it is possible to prevent the battery module2from being tilted by an external force so as for the battery modules2A to2G to be secured stably.

The direction of the vector Va in the instant embodiment corresponds to an example of the direction of a component along the stacking direction of the battery modules in a first vector having the first fixed point as a start point and the second fixed point as end point according to the present invention whereas the direction of the vector Vb in the instant embodiment corresponds to an example of the direction of a component along the stacking direction of the battery modules in a second vector having the third fixed point as a start point and the fourth fixed point as end point according to the present invention. The bolt261in the instant embodiment corresponds to an example of the bolt according to the present invention.

Note that the embodiments described above are presented in order to facilitate understanding of the present invention and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is deemed to also include all design modifications and equivalents belonging to the technical scope of the present invention.

For example, on one side of the module stack body20, the structure described in the first embodiment (so as to be configured to include two connecting members41,42and two reinforcing members51and52) may be provided, and, on the other surface of the module stack body20, the structure described in the second embodiment (so as to be configured to include a single connection member41and two reinforcing members51B,52B) may be provided.