Battery module

Abstract

A battery module (1) comprises: a battery layered body (10) that is formed from a plurality of battery cells (11) that have been layered along a Z direction; a pair of pressure applying bodies (20, 30) that sandwich both end surfaces of the battery layered body (10) in the Z direction and apply pressure to the battery layered body (10) along the Z direction; an elastic body (80) that links the pair of pressure applying bodies (20, 30) and pulls the pair of pressure applying bodies (20, 30) in the direction of approaching each other; and a drive mechanism (40) that can cause the pressure applying body (30) to move along the Z direction.

Description

Technical Field

[0001] The present invention relates to a battery module.

Background Art

[0002] A restraining structure is known that includes a restraining band that restrains the outer periphery of a battery pack formed by stacking a plurality of battery cells while applying pressure in the stacking direction of the battery cells, and a restraining force variable device provided at the joint end of the restraining band (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the prior art, there is a problem that the restraining force variable device cannot withstand a high pressing force.

[0005] The problem to be solved by the present invention is to provide a battery module with high durability against the pressing force applied to the battery laminate.

Means for Solving the Problems

[0006] The present invention solves the above problems by providing a pair of pressing bodies that sandwich a battery laminate composed of a plurality of battery cells stacked along a first direction, an elastic body that connects the pair of pressing bodies and pulls the pair of pressing bodies in a direction approaching each other, and a drive mechanism capable of moving at least one of the pressing bodies along the first direction.

Effects of the Invention

[0007] According to the present invention, the durability against the pressing force applied to the battery laminate can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a perspective view of a battery module in an embodiment of the present invention. [Figure 2] Figure 2 is a plan view of the drive mechanism in an embodiment of the present invention. [Figure 3] Figure 3 is a side view taken from direction III in Figure 2. [Figure 4] Figure 4 is a cross-sectional view along the line IV-IV in Figure 2. The left diagram shows the state of the battery cell before self-discharge occurs, and the right diagram shows the state of the battery cell after self-discharge occurs. [Figure 5] Figure 5 is an enlarged cross-sectional view of section V in Figure 4. [Figure 6] Figure 6 is a plan view of the drive mechanism in a modified example. [Figure 7] Figure 7 is a cross-sectional view of the fitting portion in a modified example. [Figure 8] Figure 8 is a cross-sectional view of the second pressurizing body in a modified example. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will now be described with reference to the drawings. Figure 1 is a perspective view of the battery module in this embodiment. Figure 2 is a plan view of the drive mechanism in this embodiment. Figure 3 is a side view taken from direction III in Figure 2. Figure 4 is a cross-sectional view taken along line IV-IV in Figure 2, where the left figure shows a cross-sectional view before self-discharge of the battery cell occurs, and the right figure shows a cross-sectional view after self-discharge of the battery cell occurs. Figure 5 is an enlarged cross-sectional view of section V in Figure 4. In the figures, the battery module 1 is shown in a vertical position for convenience, but the battery module 1 may be placed horizontally inside the battery pack mounted in the vehicle.

[0010] As shown in Figure 1, the battery module 1 in this embodiment comprises a battery stack 10, a first pressurizing body 20, a second pressurizing body 30, a drive mechanism 40, and an elastic body 80.

[0011] The battery stack 10 in this embodiment is composed of a plurality of battery cells 11. The plurality of battery cells 11 in this embodiment are not particularly limited, but are all solid-state batteries. The battery cells 11 may also be lithium-ion secondary batteries containing an electrolyte.

[0012] In this embodiment, multiple battery cells 11 are stacked on top of each other along the Z direction in the figure. The electrode tabs of adjacent battery cells 11 are electrically connected, thereby electrically connecting the multiple battery cells 11 to each other. The electrode tabs may be joined by welding or the like, or they may be electrically connected via busbars. The Z direction in this embodiment corresponds to an example of the "first direction" in the present invention.

[0013] Both end faces of the battery stack 10 in the Z direction are held between a pair of pressurizing bodies 20 and 30, and the battery stack 10 is pressurized along the Z direction by the pair of pressurizing bodies 20 and 30.

[0014] The first pressurizing body 20 is in contact with the battery stack 10 from the -Z direction side. In this embodiment, the first pressurizing body 20 is fixed inside the battery pack, although it is not shown in the figures. The first pressurizing body 20 may be movable along the first direction, similar to the second pressurizing body 30 described later.

[0015] The first pressurizing body 20 includes a plate-shaped main body portion 21 and a plurality (four in this example) of spring fixing portions 22. The plate-shaped main body portion 21 is a rigid plate-shaped member and is not particularly limited, but is made of a metal such as aluminum or stainless steel. This plate-shaped main body portion 21 abuts against the end face of the battery stack 10 in the -Z direction.

[0016] The spring fixing portion 22 is provided around the battery laminate 10 in the plate-shaped main body portion 21. The spring fixing portion 22 is a portion for fixing one end of the elastic body 80. Although not particularly limited, the spring fixing portion 22 in the present embodiment has a cylindrical shape, and one end of the elastic body 80 is fixed inside thereof.

[0017] As shown in FIGS. 1 and 3, the second pressing body 30 is in contact with the battery laminate 10 from the +Z direction side. The second pressing body 30 in the present embodiment is movable along the Z direction.

[0018] This second pressing body 30 includes a plate-shaped main body portion 31 and a plurality (four in this example) of cylindrical portions 32. The plate-shaped main body portion 31 is a plate-shaped member having rigidity, and although not particularly limited, it is made of a metal such as aluminum or stainless steel. This plate-shaped main body portion 31 is in contact with the end face of the battery laminate 10 in the +Z direction.

[0019] As shown in the left figure of FIG. 4, the plate-shaped main body portion 31 has a plurality (four in this example) of fitting holes 311. The fitting holes 311 are through holes penetrating the plate-shaped main body portion 31, and the fitting portions 321 of the cylindrical portions 32 are fitted into the fitting holes 311.

[0020] The cylindrical portions 32 are inserted into the fitting holes 311. The cylindrical portions 32 are provided around the battery laminate 10. The cylindrical portions 32 may be made of a metal or the like, similar to the plate-shaped main body portion 31. The cylindrical portions 32 in the present embodiment are separate from the plate-shaped main body portion 31 and are not integrally formed.

[0021] The cylindrical portion 32 includes a fitting portion 321, an extending portion 322, a bottomed hole 323, and a spring fixing portion 324. The fitting portion 321 is provided at the upper end of the cylindrical portion 32 and is fitted into the fitting hole 311 of the plate-shaped main body portion 31. The fitting portion 321 in the present embodiment includes a tapered fitting surface 321a. The fitting surface 321a is a surface that contacts the inner wall of the fitting hole 311, and the contact surface 311a with the fitting surface 321a of this inner wall includes a surface shape corresponding to the fitting surface 321a.

[0022] An extension portion 322 extends from this fitting portion 321 along the -Z direction. The extension portion 322 is the part that accommodates the lead screw 68 and the contact body 70, which will be described later, and is also the part that is pressed in the -Z direction by the contact body 70.

[0023] A bottomed hole 323 is formed in the fitting portion 321 and the extended portion 322. This bottomed hole 323 is open in the fitting portion 321, while being closed at the tip of the extended portion 322.

[0024] A spring fixing portion 324 is provided at the tip of the extended portion 322. This spring fixing portion 324 is the part that fixes the other end of the elastic body 80. Although not particularly limited, in this embodiment the spring fixing portion 324 is cylindrical with a through hole along the Y direction, and the other end of the elastic body 80 is fixed inside it.

[0025] The drive mechanism 40 shown in Figure 1 is electronically controlled and can move the second pressurizing body 30 along the Z direction. More specifically, this drive mechanism 40 is electronically controlled by a control system such as an ECU mounted on the vehicle. As a result, the drive mechanism 40 can control the pressure applied to the battery stack 10 by the first and second pressurizing bodies 20 and 30. In this embodiment, the drive mechanism 40 can move the second pressurizing body 30 along the Z direction in response to changes in the thickness of the battery stack 10 caused by charging and discharging when the battery cells 11 are used.

[0026] As shown in Figures 1, 2, and 4, the drive mechanism 40 in this embodiment comprises a pair of support plates 41a and 41b, a motor 50, a transmission mechanism 60, and a contact body 70 (see Figure 4). The pair of support plates 41a and 41b are part of the gearbox and support the transmission mechanism 60.

[0027] As shown in Figures 2 and 3, the motor 50 is the drive source and transmits power to the contact body 70 (see Figure 4) via the transmission mechanism 60. While the motor 50 is not particularly limited, a stepping motor can be used. Alternatively, a servo motor may be used as the motor 50. However, the type of motor 50 is not limited to those described above.

[0028] The transmission mechanism 60 transmits power from the motor 50 to the contact body 70 (see Figure 4). This transmission mechanism 60 comprises a shaft 61, a worm (screw gear) 62, a worm wheel 63, a rotating shaft 64, a plurality (four in this example) of first sprockets 65, a plurality (four in this example) of chains 66, a plurality (four in this example) of second sprockets 67, and a plurality (four in this example) of lead screws 68.

[0029] The shaft 61 is rotatable in the axial direction by the power of the motor 50. A worm 62 is provided at the tip of this shaft 61. The worm 62 has a cylindrical shape and has screw-shaped (helical) teeth on its outer circumference. This worm 62 can rotate in conjunction with the rotation of the shaft 61. A worm wheel 63 meshes with this worm 62. The worm wheel 63 is a spur gear that can rotate around the rotation axis 64. The worm 62 and worm wheel 63 described above constitute a worm gear. In the worm gear of this embodiment, the worm 62 is provided on the motor 50 side, and the worm wheel 63 is provided on the contact body 70 (see Figure 4) side.

[0030] In this embodiment of the worm gear, the worm wheel 63 can be rotated via the worm 62 by power from the motor 50. On the other hand, even if a force is applied to the worm wheel 63 in the direction of rotation, the worm 62 cannot be rotated due to the frictional force between the worm wheel 63 and the worm 62.

[0031] Four first sprockets 65 are fixed to the rotating shaft 64. Each of these first sprockets 65 is rotatable in conjunction with the rotation of the rotating shaft 64, and a chain 66 is meshed with each first sprocket 65. Each chain 66 is meshed with a second sprocket 67 fixed to a lead screw 68, and the rotation of the first sprockets 65 is transmitted to the second sprockets 67, thereby rotating the lead screw 68. As shown in Figure 3, the lead screw 68 penetrates the support plate 41b and extends into the interior of the cylindrical portion 32 of the pressurizing body 30. As shown in Figure 5, this lead screw 68 has a helical screw groove 68a on its outer circumferential surface.

[0032] As shown in the left diagram of Figure 4, a contact body 70 is provided on the lead screw 68. The contact body 70 is movable along the Z direction by power from the motor 50. As shown in Figure 5, the contact body 70 has a cylindrical shape and includes a helical screw groove 70a on its inner circumferential surface that engages with the screw groove 68a. In Figure 5, for convenience, the screw grooves 68a and 70a are slightly separated, but in reality, at least a portion of them are screwed together. Therefore, the contact body 70 can move along the first direction as the lead screw 68 rotates.

[0033] As shown in the left diagram of Figure 4 and in Figure 5, the contact body 70 can contact the locking surface 323a formed in the bottomed hole 323. The locking surface 323a is a plane that extends in a direction perpendicular to the extending direction (Z direction) of the extending portion 322 (XY direction). Therefore, by pressing the locking surface 323a, the contact body 70 can press the second pressurizing body 30 in the -Z direction. As a result, the plate-shaped main body portion 31 of the pressurizing body 30 can pressurize the battery stack 10.

[0034] In the drive mechanism 40 configured as described above, the motor 50 is electronically controlled to move the second pressurizing body 30 in the first direction, thereby controlling the magnitude of the pressure applied by the second pressurizing body 30 to the battery stack 10. More specifically, by controlling the second pressurizing body 30 to follow the thickness change of the battery stack 10 caused by the charging and discharging of the battery cells 11, the pressure applied from the second pressurizing body 30 to the battery stack 10 can be adjusted to an appropriate range.

[0035] As shown in Figure 1, the elastic body 80 is provided between the spring fixing parts 22 and 324 and connects the first pressurizing body 20 and the second pressurizing body 30. The elastic body 80 is not particularly limited, but a coil spring can be used. Alternatively, a rubber band or the like may be used as the elastic body 80.

[0036] The elastic body 80 pulls the first pressurizing body 20 and the second pressurizing body 30 in a direction that brings them closer together. In other words, in this embodiment, the elastic body 80 pulls the first pressurizing body 20 in the +Z direction and the second pressurizing body 30 in the -Z direction. As a result, the second pressurizing body 30 pressurizes the battery stack 10 not only by the pressing force applied from the contact body 70, but also by the tensile force applied from the elastic body 80.

[0037] With the battery module 1 as described above, the drive mechanism 40 and the elastic body 80 can apply force to the second pressurizing body 30. Therefore, the pressurizing force can be distributed between the drive mechanism 40 and the elastic body 80, and even when a high pressurizing force is applied to the battery stack 10, the drive mechanism 40 and the elastic body 80 can withstand the high pressurizing force. As a result, the durability of the battery module 1 is improved.

[0038] In particular, in this embodiment, a motor 50 is used as the drive source for the drive mechanism 40, and a gear-reduced screw mechanism is used as the transmission mechanism 60 and contact body 70 that transmit the power of the motor 50. Therefore, even when the amount of expansion and contraction of the battery stack 10 increases and the amount of movement of the second pressurizing body 30 along the first direction increases, it is easy to control the torque of the motor 50 and the pressure (load) from the second pressurizing body 30 to a constant level. In other words, the battery module 1 in this embodiment has excellent controllability of the pressure applied to the battery stack 10. For example, when a link-type jack is used as the drive mechanism, the pressure tends to change depending on the angle of the jack's link, but in this embodiment, the pressure can be kept constant regardless of the position of the second pressurizing body 30. As an example of when the amount of expansion and contraction of the battery stack 10 increases, one example is when an all-solid-state battery is used as the battery cell 11.

[0039] Furthermore, in this embodiment, in addition to the drive mechanism 40, force can be applied to the second pressurizing body 30 by the elastic body 80. Since the drive mechanism 40 is driven by electronic control, it requires power to operate, and cannot be driven if power is not supplied. For example, if the battery module 1 is installed in a vehicle and the vehicle's ignition switch is turned off and the control system is also turned off, the drive mechanism 40 may not be able to operate. On the other hand, if the vehicle is left idle for a long time, the battery cells 11 may self-discharge, which may reduce the thickness of the battery stack 10.

[0040] In this case, as shown in the right-hand diagram of Figure 4, the battery stack 10 contracts, and the contact body 70 separates from the locking surface 323a. However, because the elastic body 80 pulls the second pressurizing body 30, the plate-shaped main body 31 of the second pressurizing body 30 follows the contraction of the battery stack 10, and the plate-shaped main body 31 does not separate from the battery stack 10, allowing the battery stack 10 to be pressurized. In other words, the elastic body 80 brings the pressurizing bodies 20 and 30 closer to each other along the Z direction in response to the decrease in the thickness of the battery stack 10 due to the self-discharge of the battery cells 11. Thus, with the battery module 1 in this embodiment, it is possible to follow the decrease in the thickness of the battery stack 10 due to the self-discharge of the battery cells 11, even when the drive mechanism 40 is not operating.

[0041] Furthermore, in this embodiment, the elastic body 80 pressurizes all the battery cells 11 along the Z direction via the first and second pressurizing bodies 20 and 30. This makes it possible to miniaturize the battery module 1 compared to the case where elastic bodies are placed between the battery cells 11 and each battery cell is individually pressurized by the elastic bodies.

[0042] Furthermore, in this embodiment, since the drive mechanism 40 is equipped with multiple contact bodies 70, the second pressurizing body 30 can be moved along the Z direction while maintaining the orientation of the second pressurizing body 30 so that it is substantially parallel to the battery cell 11 (substantially parallel to the XY plane in the figure). Specifically, in this embodiment, since power is transmitted from one worm gear to all the lead screws 68, the rotational phase angles of all the lead screws 68 can be made the same. This makes it possible to equalize the pressure applied to the battery stack 10 at the end face of the battery stack 10.

[0043] As shown in Figure 6, in a transmission mechanism 60 having multiple pairs of lead screws 68, each pair of lead screws 68 may be controlled independently. Figure 6 is a plan view of a modified drive mechanism 40.

[0044] In this modified version, the two pairs of lead screws 68 are independently controlled by power from separate motors 50. With this modified version, for example, even if the battery cell 11 does not expand uniformly, the second pressurizing body 30 can be moved along the Z-direction while maintaining its position approximately parallel to the battery cell 11. The case where the battery cell 11 does not expand uniformly is, for example, when the central part of the battery cell 11 bulges significantly. In such a case, the main surface of the battery cell 11 becomes a convex curved surface.

[0045] Furthermore, in this embodiment, as shown in Figure 4, the mating surface 321a has a tapered shape. The plate-shaped main body portion 31 of the second pressurizing body 30 may deform into a convex shape when pressurized, but because the mating surface 321a has a tapered shape, the cylindrical portion 32 is less affected by the deformation of the plate-shaped main body portion 31. For example, if the mating surface is a surface parallel to the Z direction or horizontal to the Z direction, the cylindrical portion 32 may tilt in the +X direction as the plate-shaped main body portion 31 deforms, causing interference between the lead screw 68 or the contact body 70 and the inner wall of the cylindrical portion 32. When this interference occurs, problems such as the movement of the contact body 70 in the first direction may occur. On the other hand, in this embodiment, because the cylindrical portion 32 is less affected by the deformation of the plate-shaped main body portion 31 due to the tapered mating surface 321a, the cylindrical portion 32 is less likely to tilt, and the battery stack 10 can be stably pressurized by the second pressurizing body 30.

[0046] Figure 7 is a cross-sectional view of the fitting portion 321 in a modified example. In the above embodiment, the fitting surface 321a of the fitting portion 321 is tapered, but it is not limited to this. For example, as shown in Figure 7, the fitting surface 321a may be curved. In this case as well, the battery stack 10 can be stably pressurized by the second pressurizer 30, similar to the above.

[0047] Furthermore, as shown in Figure 3, in this embodiment, the contact surface 31a of the plate-shaped main body 31 with the battery stack 10 is planar, but this is not limited to this. The contact surface 31a may include a convex shape that protrudes toward the battery stack 10. Figure 8 is a cross-sectional view of the second pressurizing body 30 in a modified example.

[0048] As shown in the left diagram of Figure 8, the cross-section of the plate-shaped main body 31 has an aspherical shape, and the contact surface 31a may have a curved shape. Alternatively, as shown in the left diagram of Figure 8, the contact surface 31a may have a tapered shape. In this way, because the contact surface 31a includes a convex shape that protrudes toward the battery stack 10, even if the plate-shaped main body 31 deforms to bend due to the load, as described above, the contact surface 31a can appropriately press against the end face of the battery stack 10, so that pressure can be applied uniformly to the end face. Note that if the deformation of the plate-shaped main body 31 is suppressed by constructing it from a highly rigid metal such as SUS, the weight of the plate-shaped main body 31 will increase. In contrast, in this embodiment, by allowing a certain degree of deformation of the plate-shaped main body 31, the plate-shaped main body 31 can be constructed from a lighter material, thereby reducing the weight of the battery module 1.

[0049] Furthermore, as shown in Figure 2, in this embodiment, the transmission mechanism 60 includes a worm 62 provided on the motor 50 side and a worm gear with a worm wheel 63 provided on the contact body 70 side. The worm wheel cannot be rotated by force from the contact body 70 side due to the frictional force with the worm 62. As a result, when the vehicle's power is turned off, the pressure on the battery stack 10 can be maintained without adding a mechanism to lock the motor 50. For example, in hydraulic mechanisms such as hydraulics, it is necessary to add devices such as check valves and accumulators to maintain pressure when the hydraulic pump is stopped, and it is fundamentally difficult to maintain that pressure without power for a long period of time.

[0050] In this embodiment, the first pressurizing body 20 does not move along the first direction, but is not limited to this. The first pressurizing body 20 may have a cylindrical portion, similar to the second pressurizing body 30, without being fixed. In this case, the second pressurizing body 30 can be made movable along the first direction by adding a drive mechanism 40 and a contact body 70, similar to the second pressurizing body 30. [Explanation of Symbols]

[0051] 1…Battery module 10…Battery stack 11…Battery cell 20...First pressurized body 21...Plate-shaped main body 22... Spring fixing part 30...Second pressurized body 31... Plate-shaped main body 31a…Contact surface 311…Matching hole 311a…Contact surface 32...Cylindrical part 321...Matching part 321a…Mating surface 322...Extension part 323…Bottomed hole 323a…Latching surface 324... Spring fixing part 40…Drive mechanism 41a, 41b...Support plate 50...motor 60…Transmission mechanism 61... Shaft 62... Worm gear (screw gear) 63... Worm wheel 64... Rotation axis 65...First sprocket 66... ​​Chain 67...Second sprocket 68... Lead screw 68a... Thread groove 70...Contact body 71…Inner peripheral surface 80... Elastic body

Claims

1. A battery stack consisting of multiple battery cells stacked along a first direction, A pair of pressurizing bodies that clamp both end faces of the battery stack in the first direction and pressurize the battery stack along the first direction, An elastic body connects the pair of pressurizing bodies and pulls the pair of pressurizing bodies toward each other, A battery module comprising a drive mechanism capable of moving at least one of the pressurized bodies along the first direction.

2. In the battery module according to claim 1, The elastic body is a battery module that pressurizes all the battery cells along the first direction via the pair of pressurizing bodies.

3. In the battery module according to claim 2, The drive mechanism moves at least one of the pressurizing bodies along the first direction in response to changes in the thickness of the battery stack caused by charging and discharging when the battery cells are used. The elastic body is a battery module that brings the pair of pressurized bodies closer together along the first direction in response to a decrease in the thickness of the battery stack due to the self-discharge of the battery cells.

4. In the battery module according to claim 1 or 2, The aforementioned drive mechanism is Power source and The system comprises a plurality of contact bodies that are provided so as to be in contact with the pressurizing body and that are movable along the first direction by power from the drive source, The drive mechanism is a battery module that moves the pressurizing body along a first direction while maintaining the posture of the pressurizing body so that it is substantially parallel to the battery cell by the plurality of contact bodies.

5. In the battery module according to claim 1 or 2, The pressurizing body is A plate-shaped main body having a fitting hole, It comprises a fitting portion that fits into the fitting hole, and a cylindrical portion that extends from the plate-shaped main body portion along the first direction, The aforementioned drive mechanism is A rod-shaped feed screw housed inside the cylindrical part and having screw grooves on its outer surface, A contact body having an inner circumferential surface that screws into the screw groove and capable of moving along the first direction by the rotation of the feed screw to press against the cylindrical portion, The fitting portion includes a tapered or curved surface that contacts the inner wall of the fitting hole in the battery module.

6. In the battery module according to claim 1 or 2, The pressurizing body comprises a plate-shaped main body portion having a contact surface that contacts the battery stack, The contact surface includes a battery module with a convex shape that protrudes toward the battery stack.

7. A battery module according to claim 1 or 2, The aforementioned drive mechanism is Power source and A contact body provided so as to be in contact with the pressurizing body and movable along the first direction by power from the drive source, The device comprises the aforementioned drive source and a transmission mechanism interposed between the contact body and transmitting power from the drive source to the contact body, The transmission mechanism includes a worm gear, The worm gear is, A worm gear provided on the drive source side, The contact body side includes a worm wheel that meshes with the worm, The worm wheel is a battery module that cannot be rotated by a force from the contact body side due to the frictional force with the worm.

8. A battery module according to claim 1 or 2, The aforementioned drive mechanism is a battery module equipped with a motor as a drive source.

9. A battery module according to claim 8, The pressurizing body is Plate-shaped main body, It comprises a cylindrical portion extending from the plate-shaped main body portion along the battery stack, The aforementioned drive mechanism is A rod-shaped feed screw is housed inside the cylindrical portion, is rotatable by power from the drive source, and has screw grooves on its outer surface, The system further comprises a contact body having an inner circumferential surface that screws into the screw groove, and which moves along the first direction by the rotation of the feed screw to press against the cylindrical portion, The elastic body is a battery module connected to the cylindrical portion.

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