CN210142671U - Battery module - Google Patents

Abstract

The utility model provides a battery module can make a plurality of monocell unit cascade allocation between the end plate and need not exert high initial load, and to the load change of applying to the end plate, also can deal with simple structure. The battery module includes: a single cell unit group (2) including a plurality of stacked single cell units (21); a pair of end plates (3, 4) respectively arranged at both ends of the single cell group (2) in the stacking direction; and a spring member (6) that is provided between the single cell unit group (2) and at least one of the pair of end plates (3, 4) and that can apply a load in the pressing direction to the single cell unit group (2), wherein the spring member (6) includes a first spring (61) that is disposed at a position corresponding to the central region of the single cell unit (21) and a second spring (62) that is disposed around the first spring (61), and the spring constant of the first spring (61) is greater than the spring constant of the second spring (62).

Description

Battery module

Technical Field

The utility model relates to a battery module (battery module), battery module comes a plurality of range upon range of monocell units (cell) of centre gripping through a pair of end plate (end plate).

Background

A battery module mounted in a hybrid vehicle (hybrid) or an electric vehicle has a single cell group including a plurality of stacked single cells arranged between a pair of end plates, and the entire single cell group is sandwiched by binding members such as binding bars (bind bars) provided across the end plates.

In addition, the unit cells may expand due to charge and discharge or deterioration. In order to suppress this expansion, a large initial load is applied to the cell unit group in a direction of compression in the stacking direction, and the entire cell unit group is forcibly pressed between the end plates. Therefore, when the cell unit group is elongated in the stacking direction due to an increase in the internal pressure of the cell unit caused by expansion, the end plates receive a considerable load.

In such a battery module, when the unit cells expand, a large load is applied to the fixing points of the bundling members and the end plates in addition to the initial load. Therefore, it is necessary to provide a flexure structure, a slide structure, or the like for the fixing point of the binding member and the end plate separately, thereby reducing the load applied to the fixing point. Further, conventionally, there has been known a battery module in which an elastic member is disposed between a battery cell group and an end plate, and a further load generated when the battery cells expand is absorbed by a rectangular plate-shaped low-elasticity rubber sponge (see, for example, patent document 1). However, the battery module also applies a large initial load (bundling load) by compressing the single cell unit group.

[ Prior art documents ]

[ patent document ]

Patent document 1: japanese patent laid-open No. 2015-230764

SUMMERY OF THE UTILITY MODEL

[ problem to be solved by the utility model ]

In all of the conventional battery modules, a large initial load is applied by compressing the unit cell group, and therefore, it is necessary to add another structure such as a flexure structure or a slide structure of a fixing point, which not only complicates the structure, but also requires a stacking facility and a stacking process for applying the initial load. Further, as the number of stacked unit cells increases, the size increase of the unit cell group when it expands due to expansion increases. Since the initial load is set in consideration of the increase in the size of the battery cell group, if the number of stacked battery cells is increased to cope with a large current, a large initial load corresponding to the increase in the number of stacked battery cells has to be applied. However, the structure of the single cell unit has a limit to the initial load that can be applied, and therefore, there is a problem in that the number of stacked single cell units is limited.

Therefore, an object of the present invention is to provide a battery module in which a plurality of single cell units can be stacked and arranged between end plates without applying a large initial load, and a simple structure can be used to cope with a load variation applied to the end plates.

[ means for solving problems ]

(1) The battery module (for example, the battery module 1 described later) of the present invention includes: a single cell unit group (for example, a single cell unit group 2 described later) including a plurality of stacked single cell units (for example, a single cell unit 21 described later); a pair of end plates (for example, end plates 3 and 4 described later) disposed at both ends of the single cell unit group in the stacking direction; and a spring member (for example, a spring member 6 described later) provided between the cell unit group and at least one of the pair of end plates (for example, an end plate 3 described later) and capable of applying a load in a pressing direction to the cell unit group, the spring member including a first spring (for example, a first spring 61 described later) disposed at a position corresponding to a central region of the cell unit and a second spring (for example, a second spring 62 described later) disposed around the first spring, and a spring constant of the first spring being larger than a spring constant of the second spring.

According to the battery module described in the above (1), the second spring having a relatively smaller spring constant than the first spring is first brought into contact with the unit cell group between the pair of end plates to support the unit cell group, so that the unit cell group can be arranged between the end plates in a stacked manner without applying a large initial load. Further, since the load from the battery cell group can be coped with by the first spring having a relatively large spring constant when the battery cells expand, it is possible to cope with the fluctuation of the load applied to the end plate with a simple configuration. Further, a stacking facility and a stacking process for applying an initial load are not required, and the number of stacked unit cells can be increased.

(2) In the battery module described in (1), there may be: the first spring is a spring capable of applying a load to the single cell unit group against a load acting on the end plate due to an increase in internal pressure when the single cell units expand, and the second spring is a spring capable of applying a load to the single cell unit group corresponding to a load required to maintain an initial stacked state.

According to the battery module described in the above (2), an appropriate load can be applied to the single cell unit group by each of the first spring and the second spring.

(3) In the battery module according to (1) or (2), there may be: in an unexpanded state of the battery cell, a load applied to the battery cell group by the second spring is greater than a load applied to the battery cell group by the first spring.

According to the battery module described in the above (3), since the load is mainly applied to the single cell unit group by the second spring having a relatively small spring constant when the single cell unit is not expanded, an unreasonable load is not applied to the single cell unit group when the single cell unit is not expanded, which does not require a large load.

(4) In the battery module according to any one of (1) to (3), there may be included: a holder (holder) member (for example, a holder member 7 described later) that is disposed between the end plate provided with the spring member and the single cell unit group and that holds the spring member, the holder member including: a flat plate portion (for example, a flat plate portion 71 described later) that is in contact along an inner surface (for example, an inner surface 3a described later) of the end plate, and that holds the second spring between the flat plate portion and the single cell unit group; and a recess (for example, a recess 72 described later) provided so as to protrude toward the single cell unit group with respect to the flat plate portion, and having flexibility for accommodating and holding the first spring with the end plate.

According to the battery module described in the above (4), the spring member having the first spring and the second spring can be easily arranged and held between the battery cell and the end plate. Further, the first spring having a relatively large spring constant is accommodated in the recess of the holder member from the end plate side, and does not directly contact the battery cell, so that the risk of damage to the battery cell due to a large load of the first spring can be avoided.

(5) In the battery module according to any one of (1) to (4), the first spring may include a coil spring, and the second spring may include a plate spring.

According to the battery module described in the above (5), since the dimensions of the first spring and the second spring when compressed can be reduced, the spring member can be configured to be compact as a whole, and the battery module can be prevented from being increased in size.

(6) In the battery module according to any one of (1) to (5), there may be included: a space holding member (e.g., a tie rod (tie rod)5 described later) is disposed between the facing inner side surfaces of the pair of end plates to hold the space between the pair of end plates at a fixed space.

According to the battery module described in the above (6), since the minimum interval between the pair of end plates is limited by the length of the interval-maintaining member, it is possible to prevent an excessive initial load from being applied to the single cell unit group. In addition, since the interval between the pair of end plates can be easily maintained at a fixed interval, the assembly work of the battery module is also facilitated.

[ effects of the utility model ]

According to the present invention, it is possible to provide a battery module in which a plurality of single cell units can be stacked and arranged between end plates without applying a large initial load, and a simple structure can be used to cope with a load change applied to the end plates.

Drawings

Fig. 1 is an exploded perspective view showing an end plate of a battery module according to the present invention in an exploded manner.

Fig. 2A is an exploded perspective view of an end plate of a battery module according to the present invention, as viewed from one direction.

Fig. 2B is an exploded perspective view of the end plate of the battery module of the present invention viewed from another direction.

Fig. 3 is a side view of a main portion of one end of the battery module of the present invention.

Fig. 4 is a cross-sectional view of the battery module along the line a-a in fig. 3 when the unit cells are not expanded.

Fig. 5 is a cross-sectional view of the battery module taken along the line B-B in fig. 3 when the unit cells are not expanded.

Fig. 6 is a sectional view of the battery module when the unit cells are expanded, the sectional view being taken along the same line a-a in fig. 3.

Fig. 7 is a sectional view of the battery module when the unit cells are expanded, the sectional view being taken along the same line B-B in fig. 3.

Fig. 8 is a graph showing a relationship between the stroke (stroke) and the load of the first spring and the second spring of the end plate.

[ description of symbols ]

1: battery module

2: single cell unit group

21: single cell unit

3. 4: end plate

3 a: inner side (of end plate 3)

4 a: inner side (of end plate 4)

6: spring member

61: first spring

62: second spring

5: pull rod (spacing holding member)

7: support component

71: flat plate part

72: concave part

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Fig. 1 is an exploded perspective view showing end plates of a battery module according to the present invention. Fig. 2A is an exploded perspective view of an end plate of a battery module according to the present invention, as viewed from one direction. Fig. 2B is an exploded perspective view of the end plate of the battery module of the present invention viewed from another direction. Fig. 3 is a side view of a main portion of one end of the battery module of the present invention. Fig. 4 is a cross-sectional view of the battery module along the line a-a in fig. 3 when the unit cells are not expanded. Fig. 5 is a cross-sectional view of the battery module taken along the line B-B in fig. 3 when the unit cells are not expanded.

As shown in fig. 1, the battery module 1 includes: a single cell unit group 2; a pair of end plates 3, 4 disposed at both ends of the unit cell group 2 to sandwich the unit cell group 2; a plurality of (four in the present embodiment) tie rods 5 spanning between the pair of end plates 3, 4; a spring member 6 disposed between one of the end plates 3 and the single cell unit group 2; and a holder member 7 holding the spring member 6.

In addition, of the directions indicated by the arrows in the drawings of the present specification, the direction along the direction D1 represents the longitudinal direction of the battery module 1. The direction along the direction D2 represents the width direction of the battery module 1. The direction along the direction D3 represents the height direction of the battery module 1. The direction D3 represents the "up" of the battery module 1, and the opposite direction represents the "down" of the battery module 1.

The battery cell group 2 is formed by stacking a plurality of rectangular parallelepiped battery cells 21 along the direction D1. The unit cell 21 is configured by housing an electrode body (not shown) in a cell case made of aluminum, aluminum alloy, or the like, and has a pair of positive and negative electrode terminals 22 and 22 on the upper surface. Generally, the electrode terminals 22 and 22 of the unit cells 21 and 21 adjacent to each other in the stacking direction (direction D1) are electrically connected to each other by a bus bar (not shown). Thereby, all the battery cells 21 of the battery cell group 2 are electrically connected in series or in parallel. Insulating spacers (not shown) are disposed between the unit cells 21, 21 adjacent to each other in the stacking direction, and are sandwiched between the unit cells 21, 21.

The end plates 3 and 4 are formed of a metal material such as aluminum or an aluminum alloy, a resin material such as engineering plastic (engineering plastic), or a laminate of a metal material and a resin material, and each includes a plate-like member having an area slightly larger than an end face in the lamination direction of the unit cell group 2. Bolt insertion holes 31, 41 are provided at four corners of the end plates 3, 4. The end plates 3, 4 are fixed by bolts 51 to tie rods 5 disposed across and between the opposing inner side surfaces 3a, 4a with the single cell unit group 2 interposed therebetween.

The tie bar 5 includes a rod-shaped member extending straight (straight) in the stacking direction of the unit cells 21, and two tie bars are disposed on both side portions of the unit cell group 2. The inner side surfaces 3a and 4a of the end plates 3 and 4 facing each other abut against both end surfaces of the tie bar 5. In this state, the bolts 51 are inserted through the bolt insertion holes 31 and 41 from the outside of the end plates 3 and 4, and thereby the end plates 3 and 4 are fixed so as to sandwich the tie rods 5 from both sides. Thereby, the movement of the end plates 3, 4 in the direction of approaching each other is prevented by the tie bars 5. That is, the end plates 3 and 4 are disposed at both ends of the single cell group 2, respectively, with a fixed interval defined by the length L1 of the tie bar 5.

By fixing the end plates 3, 4 to the tie bar 5 in this manner, the minimum distance between the end plates 3, 4 is limited by the length L1 of the tie bar 5. Therefore, when the end plates 3 and 4 are fixed, an excessive initial load can be prevented from being applied to the single cell unit group 2. Further, since the interval between the pair of end plates 3 and 4 can be easily maintained at a fixed interval, the assembly work of the battery module 1 is also facilitated. The pull rod 5 corresponds to an interval maintaining member in the present invention.

The length L1 of the tie bar 5 is greater than the length L2 of the cell unit group 2 in the stacking direction in the initial stacked state. Specifically, the length L1 of the tie bar 5 is set to a length of approximately: even when the cell unit group 2 is maximally extended in the stacking direction due to the increase in internal pressure caused by the expansion of the cell unit 21, the cell unit group 2 is converged between the pair of end plates 3 and 4. In other words, even if the unit cell group 2 is elongated, the interval between the pair of end plates 3 and 4 is not changed. The unit cell group 2 shown in the present embodiment is disposed in close contact with the end plate 4, with the inner surface 4a of the end plate 4 of the pair of end plates 3 and 4 as a reference surface. Therefore, a gap S (see fig. 3) corresponding to the difference between L1 and L2 exists between the end plate 3 fixed to the tie bar 5 and the initially stacked unit cell group 2.

The initial stacked state of the unit cell group 2 means a state in which the plurality of unit cells 21, each in an unexpanded state, are closely stacked on each other in the direction D1 with the spacer interposed therebetween. In the battery cell group 2 at this time, substantially no load equal to or greater than a load is applied to the extent that the stacked state in which the adjacent battery cells 21, 21 are in close contact with each other can be maintained. That is, a large initial load that compresses the battery cells 21 in the stacking direction as in the conventional art is not applied to the battery cell group 2 in the initial stacked state.

The spring member 6 is disposed in the gap S between the end plate 3 and the single cell unit group 2. Specifically, the spring member 6 is provided between the end plate 3 and the cell unit 21 disposed at the end portion on the end plate 3 side in the cell unit group 2. The spring member 6 includes a spring that exerts an elastic repulsive force on the single cell unit group 2 in a direction toward the other end plate 4. Thus, the spring member 6 can apply a load in a direction pressing the cell unit group 2 along the stacking direction of the cell units 21 (a direction toward the other end plate 4). In the present embodiment, the spring member 6 is not disposed on the other end plate 4 side.

The spring member 6 includes a first spring 61 and a second spring 62. The first spring 61 and the second spring 62 are held by the end plate 3 via the holder member 7.

The first spring 61 is disposed at a position corresponding to the central region of the end plate 3. The central region of the end plate 3 corresponds to the central region of the cell unit 21 (the central region of the surface of the cell unit 21 that faces the end plate 3). On the other hand, the second spring 62 is disposed around the first spring 61. Also, the spring constant of the first spring 61 is larger than that of the second spring. Therefore, in the strokes when the first spring 61 and the second spring 62 are compressed against the elastic repulsive force, the load exerted by the elastic repulsion of the first spring 61 is larger than the load exerted by the elastic repulsion of the second spring 62 (see fig. 8).

Specifically, the first spring 61 may be a spring that can apply a load to the cell unit group 2 against a load applied to the end plate 3 due to an increase in internal pressure during expansion caused by charge and discharge or deterioration of the cell unit 21. The second spring 62 may be a spring that can apply a load corresponding to the load required to maintain the initial stacked state to the single cell unit group 2. Thus, the battery module 1 can apply appropriate loads to the single cell group 2 by the first spring 61 and the second spring 62.

The specific type of spring used for the first spring 61 and the second spring 62 is not particularly limited as long as it can apply a desired load to each of the single cell unit groups 2, but in the present embodiment, the first spring 61 includes a coil spring formed in a ring shape, and the second spring 62 includes a plate spring bent in a substantially U-shape. These springs can be made smaller in size than a coil spring or the like when compressed, and the spring member 6 can be formed compact as a whole. Therefore, the gap S between the end plate 3 and the unit cell group 2 can be reduced, and accordingly, the size increase of the battery module 1 can be suppressed.

In the present embodiment, the first spring 61 includes two coil springs, and the second spring 62 includes four leaf springs, but the number of the springs is appropriately set in accordance with a required load applied to the unit cell group 2, and the number is not limited to any number shown in the present embodiment.

The holder member 7 is made of resin such as Polypropylene (PP) or Polyethylene (PE), and is disposed between the end plate 3 and the unit cells 21 at the end of the unit cell group 2. The holder member 7 includes a flat plate portion 71 that contacts along the inner surface 3a of the end plate 3, and a recess portion 72 that protrudes in the direction of the unit cell 21 (in the direction opposite to the end plate 3) with respect to the flat plate portion 71. The recess 72 is formed in the flat plate portion 71 of the holder member 7 so as to be recessed toward the unit cell group 2 from the side surface facing the end plate 3. The entire holder member 7 is formed of resin, but at least the concave portion 72 has flexibility.

The flat plate portion 71 of the holder member 7 is formed substantially similarly to the outer shape of the inner surface 3a of the end plate 3. The flat plate portion 71 has notches 73 at its four corners for exposing the bolt insertion holes 31 disposed at the four corners of the end plate 3. The outer peripheral edges of the four sides of the flat plate portion 71 excluding the notch portion 73 are formed so as to be bent toward the end plate 3. Thus, fitting ridges (rib)74 that can be fitted along the respective outer peripheral edges of the four sides of the end plate 3 are provided on the respective outer peripheral edges of the four sides of the flat plate portion 71. The holder member 7 is held in contact with the inner surface 3a of the end plate 3 by fitting the fitting convex strip 74 along the outer peripheral edge of the end plate 3.

The two first springs 61 are housed in the recess 72 of the holder member 7 in parallel in the width direction (direction D2) of the battery module 1 from the end plate 3 side. Here, the inner surface 3a of the end plate 3 has a cocoon-shaped support protrusion 32 protruding toward the holder member 7 side in the same manner as the recess 72 in a central region corresponding to the recess 72 of the holder member 7. Therefore, when the holder member 7 abuts against the inner side surface 3a of the end plate 3, the support convex portion 32 of the end plate 3 enters the concave portion 72 in which the first spring 61 is accommodated, thereby sandwiching and holding the first spring 61 between the bottom wall 72a of the concave portion 72. The first spring 61 in the recess 72 at this time is not compressed at all as shown in fig. 5, and does not generate any elastic repulsive force.

The four second springs 62 are attached to the side surface of the flat plate portion 71 of the holder member 7 on the side of the unit cell group 2. The flat plate portion 71 of the holder member 7 has spring holding portions 75 at four locations around the recess 72, which portions are close to the respective cutout portions 73. The spring holding portion 75 holds the base portion 621 of the second spring 62, and thus the second spring 62 is held so as to protrude from the flat plate portion 71 of the holder member 7 toward the single cell unit group 2. The four second springs 62 are disposed so that elastic repulsive forces act on the four corners of the surface of the single cell unit 21 facing the heel end plate 3.

Here, the positional relationship of the first spring 61 and the second spring 62 is set as follows. That is, in a state where both the first spring 61 and the second spring 62 held by the end plate 3 via the holder member 7 are not compressed (a state where the end plate 3 is not yet in contact with the single cell unit group 2 and an elastic repulsive force is not yet generated), the position of the second spring 62 facing the tip end portion of the single cell unit group 2 is located at a position projecting toward the single cell unit group 2 than the first spring 61. Therefore, when the end plate 3 is gradually brought close to the unit cell group 2, the second spring 62 is compressed before the first spring 61 comes into contact with the unit cell group 2, and an elastic repulsive force acts on the unit cell group 2.

Next, an example of a flow when the battery module 1 is configured will be described.

First, between a pair of end plates 3 and 4, a unit cell group 2 in which a plurality of unit cells 2 are stacked with a spacer interposed therebetween is disposed so as to be offset toward the end plate 4. Then, the end plates 3, which have the spring members 6 (two first springs 61 and four second springs 62) held by the holder members 7, are brought into contact with the single cell unit group 2, and the respective end plates 3, 4 are fixed to the tie rods 5 by the bolts 51.

At this time, the second spring 62, which is in contact with the first spring 61 earlier, is slightly compressed to generate an elastic repulsive force, and a predetermined initial load is applied to the unit cell group 2. The initial load at this time is a relatively small load that can maintain only the stacked state of the battery cells 21, and a large initial load that strongly compresses the battery cell group 2 as in the conventional case is not applied.

The cell unit group 2 maintains the stacked state of the cell units 21 by the load applied by the second spring 62, and becomes the initial stacked state. In this way, the second spring 62 having a relatively smaller spring constant than the first spring 61 is first brought into contact with the unit cell group 2 to support the unit cell group 2, and therefore, the unit cell group 2 can be stacked between the end plates 3 and 4 without applying a large initial load to the unit cell group 2.

In the initial stacked state of the unit cell group 2, the first spring 61 does not abut against the bottom wall 72a of the recess 72, or substantially applies no load to the unit cell group 2 even if it abuts against it. That is, in the initial stacked state of the unit cell group 2, the first spring 61 is located in the stroke region on the left side of the position P1 where the load starts to be applied as shown in fig. 8, and the load is applied to the unit cell group 2 mainly by the second spring 62. Therefore, the load applied to the single cell group 2 by the first spring 61 at this time is 0 or close to 0. Therefore, an unreasonable load is not applied to the uninflated single cell group 2 that does not require a large load.

The second spring 62 shown in the present embodiment is configured to apply a load to the cell unit group 2 via the cell units 21 by abutting the cell units 21 arranged at the end portion of the cell unit group 2 on the end plate 3 side against the four corner portions of the surface facing the end plate 3. Since the four corners of the unit cell 21 are relatively high-strength portions, the second spring 62 can press the relatively high-strength portions against the unit cell group 2, and the unit cell group 2 can be stably supported even by the second spring 62 having a small spring constant.

Next, the case where the unit cell 21 expands due to charge/discharge or deterioration will be described with reference to fig. 6 and 7. Fig. 6 is a cross-sectional view of the battery module when the unit cells are expanded, the cross-sectional view being cut along the same line a-a in fig. 3. Fig. 7 is a cross-sectional view of the battery module with the cells unexpanded, taken along the same line B-B in fig. 3.

As shown in fig. 6 and 7, when the cell unit 21 expands, the cell unit group 2 expands in the stacking direction as the internal pressure of the cell unit 21 increases, and a load due to the increase in the internal pressure acts on the end plate 3 as indicated by the open arrow in the drawing. The second spring 62, which applies a load to the battery cell group 2 to maintain the initial stacked state, is gradually compressed by the load due to the increase in the internal pressure of the battery cell group 2.

When the second spring 62 is further compressed as the unit cell group 2 expands due to expansion of the unit cells 21, the elastic limit is gradually approached. However, the first spring 61 is disposed so as to come into contact with the battery cell group 2 before the second spring 62 reaches the elastic limit, and is pressed and compressed by the battery cell group 2. That is, the first spring 61 accommodated in the recess 72 is compressed toward the end plate 3 while the recess 72 is deflected by the single cell unit group 2 abutting against the bottom wall 72a of the recess 72 of the holder member 7 as it is further expanded. Thus, the first spring 61 is compressed by the unit cell group 2 to generate an elastic repulsive force before the second spring 62 reaches the elastic limit, and starts to apply a load to the unit cell group 2 without interrupting the load applied to the unit cell group 2 by the second spring 62 (position P1 in fig. 8).

When the single cell group 2 further extends, the load applied to the single cell group 2 by the first spring 61 soon exceeds the load applied to the single cell group 2 by the second spring 62 (position P2 in fig. 8). As shown in fig. 8, since the load (elastic repulsive force) with respect to the stroke when the first spring 61 is compressed is larger than the load (elastic repulsive force) with respect to the stroke when the second spring 62 is compressed, the load that the first spring 61 can apply to the single cell group 2 is larger than the load that the second spring 62 can apply to the single cell group 2. The first spring 61 can apply a load against the end plate 3 due to the increase in the internal pressure of the unit cell 21 during expansion, as described below. Therefore, after the load applied to the single cell group 2 by the first spring 61 exceeds the load applied to the single cell group 2 by the second spring 62 (the stroke region on the right side of the position P2 in fig. 8), the load is applied to the single cell group 2 mainly by the first spring 61, and thus a load that resists a large load due to an increase in the internal pressure of the single cell 21 and opposes the load is applied to the single cell group 2.

The first spring 61 at this time does not absorb a large load due to the increase in the internal pressure of the battery cell 21 as in the conventional art, but applies a load against the load to the battery cell group 2, thereby pressing the extension of the battery cell group 2. Therefore, the spring member 6 applies a load to the single cell unit group 2 by the first spring 61 and the second spring 62 having relatively different spring constants, and thereby can completely receive a load variation from a relatively small initial load to a relatively large load after an internal pressure is increased. Even if the battery cell group 2 is expanded to the maximum, the battery cell group 2 is converged within the interval between the pair of end plates 3 and 4, and the interval between the end plates 3 and 4 is maintained at the length L1 of the tie bar 5.

According to the battery module 1, it is possible to easily cope with load fluctuations that are applied to the end plates 3 from an initial load to a load due to an increase in the internal pressure of the battery cells 21 between the pair of end plates 3 and 4. Since the initial load of the large compression is not applied to the single cell group 2, the number of stacked single cells 21 can be increased without requiring a stacking facility and a stacking process for applying the initial load to the single cell group 2.

Further, the battery module 1 does not need to have a separate structure such as a flexure structure or a slide structure attached to the fixing points of the end plates 3 and 4, and has only to have the minimum strength capable of holding the single cell unit group 2, and therefore can have a simple structure.

Further, the first spring 61 having a relatively large spring constant shown in the present embodiment is housed in the recess 72 of the holder member 7, and does not directly contact the battery cell 21 because a load is applied to the battery cell group 2 via the bottom wall 72a of the recess 72. Therefore, the risk of damage to the single cell unit 21 due to the load generated by the first spring 61 can be avoided.

In the present embodiment, the spring member 6 is disposed only on one 3 side of the pair of end plates 3, 4, but the same spring member 6 may be disposed on both the end plates 3, 4. However, in the case where the spring member 6 is disposed only on one of the end plates 3 as in the present embodiment, the inner surface 4a of the other end plate 4, which does not include the spring member, can be used as a reference surface for supporting the single cell unit group 2. Therefore, from the viewpoint of more stably supporting the single cell unit group 2, it is desirable to dispose the spring member 6 only on one of the pair of end plates 3 and 4.

Claims (10)

1. A battery module, comprising:

a single cell unit group including a plurality of stacked single cell units;

a pair of end plates disposed at both ends of the single cell unit group in the stacking direction; and

a spring member provided between the cell unit group and at least one of the pair of end plates and capable of applying a load in a pressing direction to the cell unit group,

the spring member includes a first spring disposed at a position corresponding to a central region of the unit cell, and a second spring disposed around the first spring, and a spring constant of the first spring is larger than a spring constant of the second spring.

2. The battery module according to claim 1,

the first spring is a spring capable of applying a load to the battery cell group against the end plate due to an increase in internal pressure during expansion of the battery cells,

the second spring is a spring capable of applying a load corresponding to a load required to maintain an initial stacked state to the single cell unit group.

3. The battery module according to claim 1 or 2,

in an unexpanded state of the battery cell, a load applied to the battery cell group by the second spring is greater than a load applied to the battery cell group by the first spring.

4. The battery module according to claim 1 or 2, characterized by comprising:

a holder member that is disposed between the end plate provided with the spring member and the single cell unit group and holds the spring member,

the bracket member has: a flat plate portion that is in contact along an inner surface of the end plate, and holds the second spring between the flat plate portion and the single battery cell group; and a recess portion provided so as to protrude toward the single cell unit group with respect to the flat plate portion, and having flexibility for accommodating and holding the first spring with the end plate.

5. The battery module according to claim 1 or 2,

the first spring comprises a coil spring,

the second spring comprises a leaf spring.

6. The battery module according to claim 1 or 2, characterized by comprising:

and a space holding member disposed between the facing inner surfaces of the pair of end plates, for holding the space between the pair of end plates at a fixed space.

7. The battery module of claim 3, comprising:

a holder member that is disposed between the end plate provided with the spring member and the single cell unit group and holds the spring member,

the bracket member has: a flat plate portion that is in contact along an inner surface of the end plate, and holds the second spring between the flat plate portion and the single battery cell group; and a recess portion provided so as to protrude toward the single cell unit group with respect to the flat plate portion, and having flexibility for accommodating and holding the first spring with the end plate.

8. The battery module according to claim 3,

the first spring comprises a coil spring,

the second spring comprises a leaf spring.

9. The battery module according to claim 4,

the first spring comprises a coil spring,

the second spring comprises a leaf spring.

10. The battery module of claim 3, comprising:

and a space holding member disposed between the facing inner surfaces of the pair of end plates, for holding the space between the pair of end plates at a fixed space.

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