Holding mechanism

Abstract

To provide a holding mechanism that can more appropriately maintain the surface pressure applied to a laminate in an all-solid-state battery against fluctuations in load due to expansion and contraction of the laminate.SOLUTION: A holding mechanism compresses a stack of all-solid-state batteries in a stacking direction and holds a surface pressure applied to the stack, and includes a surface pressure holding unit that holds the surface pressure by hydraulic pressure in response to fluctuations in the load in the stacking direction due to expansion and contraction of the stack, a hydraulic actuating unit that operates by hydraulic pressure to apply a load to the stack in the stacking direction, and a hydraulic pump that supplies hydraulic pressure to the hydraulic actuating unit, and the maximum operating hydraulic pressure for operating the hydraulic actuating unit is lower than the maximum holding hydraulic pressure for holding the surface pressure of the surface pressure holding unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a retention mechanism. [Background technology]

[0002] A technology is known for a battery module that includes a stack of multiple single cells and a pressure adjustment member at one end of the stack in the stacking direction of the stack, which adjusts the pressure applied to the stack in the stacking direction of the stack, and the pressure adjustment member includes multiple springs that are elastically deformable in the stacking direction (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2019-125455 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology described in Patent Document 1 has a limit to the stroke amount of the pressure adjustment member, which means that when the load fluctuates greatly due to the expansion and contraction of the stack, it may not be possible to properly maintain the surface pressure applied to the stack.

[0005] The problem to be solved by the present invention is to provide a holding mechanism that can more appropriately hold the surface pressure applied to the laminate in response to fluctuations in load due to expansion and contraction of the laminate in an all-solid-state battery. [Means for solving the problem]

[0006] The present invention provides a holding mechanism that compresses a stack of all-solid-state batteries in the stacking direction and holds the surface pressure applied to the stack, and includes a surface pressure holding unit that holds the surface pressure by hydraulic pressure in response to fluctuations in the load in the stacking direction due to expansion and contraction of the stack, a hydraulic actuating unit that operates by hydraulic pressure to apply a load to the stack in the stacking direction, and a hydraulic pump that supplies hydraulic pressure to the hydraulic actuating unit, and solves the above-mentioned problem by having a maximum operating hydraulic pressure for operating the hydraulic actuating unit that is smaller than the maximum holding hydraulic pressure for holding the surface pressure of the surface pressure holding unit. [Effects of the Invention]

[0007] According to the present invention, the surface pressure applied to the laminate of the all-solid-state battery can be more appropriately maintained against fluctuations in load due to expansion and contraction of the laminate. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a front view schematically showing a battery module including a holding mechanism according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram for explaining an example of a surface pressure holding unit provided in the holding mechanism according to this embodiment. [Figure 3] FIG. 3 is a diagram for explaining changes in the state of the laminated body and the holding mechanism according to the state of the vehicle in this embodiment. [Figure 4] FIG. 4 is a top view and a cross-sectional view showing an example of a holding mechanism according to this embodiment. [Figure 5] FIG. 5 is a top view, a cross-sectional view, and a bottom view showing an example of a hydraulic motor provided in the hydraulic actuation unit according to this embodiment. [Figure 6] FIG. 6 is a top view and a cross-sectional view showing an example of a holding mechanism according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] A holding mechanism according to an embodiment of the present invention will be described with reference to the drawings. The holding mechanism according to the present embodiment is provided in a battery module of an all-solid-state battery. The battery module is installed as a battery in, for example, an electric vehicle.

[0010] FIG. 1 is a front view schematically illustrating a battery module including a holding mechanism according to an embodiment of the present invention. The battery module 1 includes a stack 10 of all-solid-state batteries, a holding mechanism 20, and an exterior member 30. In FIG. 1, the stack 10 is formed by stacking all-solid-state batteries in the X-axis direction. That is, the X-axis direction is the stacking direction in which the all-solid-state batteries are stacked. The Y-axis is the surface direction of the all-solid-state batteries, which is perpendicular to the X-axis. The battery module 1 is not limited to one, and multiple battery modules 1 may be provided. In the example of FIG. 1, the multiple battery modules 1 include three battery modules 1a, 1b, and 1c. The number of battery modules is not limited to this, and may be two or less, or four or more. As shown in FIG. 1, the battery modules 1 (1a, 1b, 1c) each include a stack 10 (10a, 10b, 10c), a holding mechanism 20 (20a, 20b, 20c), and an exterior member 30 (30a, 30b, 30c). In the following explanation, battery module 1a will be used as an example out of the multiple battery modules 1, but since the other battery modules 1b and 1c each have the same configuration and function, explanations will be omitted and the explanation of battery module 1a will be used as appropriate.

[0011] The laminate 10a is formed by stacking a plurality of all-solid-state batteries. The thickness T of the laminate 10a in the stacking direction changes as the laminate 10a expands and contracts due to charging and discharging. In particular, since the battery module according to this embodiment is used as a battery for an electric vehicle, the thickness T of the laminate 10a changes depending on the state of the vehicle. The all-solid-state battery is not particularly limited, but for example, it is formed by stacking a negative electrode layer, a negative electrode current collector foil, a solid electrolyte layer, a positive electrode layer, and a positive electrode current collector foil in the stacking direction (X-axis direction).

[0012] The negative electrode layer is an alkali metal layer mainly composed of alkali metal that is released from the positive electrode layer, reaches the negative electrode current collector foil through the solid electrolyte layer, and deposits thereon as the all-solid-state battery is charged. The negative electrode layer is a layer that deposits on the negative electrode current collector foil during charging of the all-solid-state battery, increasing in volume and decreasing in volume during discharge. The negative electrode layer is, for example, a lithium metal layer. The negative electrode layer may include a layer other than the lithium metal layer, for example, an auxiliary layer that assists the deposition of the lithium metal layer. The negative electrode current collector foil is a conductive foil-like member. The negative electrode current collector foil is, for example, a metal foil, and an example of this metal foil is copper foil. The negative electrode current collector foil may be made of a conductive resin. The negative electrode current collector foil is joined to a negative electrode tab (not shown).

[0013] The solid electrolyte layer can be, for example, a sulfide solid electrolyte or an oxide solid electrolyte, with sulfide solid electrolytes being preferred. The positive electrode layer contains at least a positive electrode active material capable of absorbing and releasing lithium (Li). While not particularly limited, lithium-containing metal oxides are preferred. That is, according to a preferred embodiment of the present invention, the positive electrode active material includes at least one selected from lithium-containing metal oxides. According to a more preferred embodiment of the present invention, the positive electrode active material is composed solely of at least one selected from lithium-containing metal oxides. Specific examples of lithium-containing metal oxides include layered rock-salt active materials such as LiCoO2, LiMnO2, LiNiO2, and Li(Ni-Mn-Co)O2; spinel active materials such as LiMn2O4 and LiNi0.5Mn1.5O4; olivine active materials such as LiFePO4 and LiMnPO4; and Si-containing active materials such as Li2FeSiO4 and Li2MnSiO4. Other oxide active materials include, for example, Li4Ti5O12 and LiVO2. Among these, Li(Ni-Mn-Co)O2 and those in which part of these transition metals is replaced with other elements (NMC composite oxides) are preferably used as the positive electrode active material. These positive electrode active materials may be used alone or in combination of two or more. The positive electrode current collector foil is a foil-like member having electrical conductivity. The positive electrode current collector foil is, for example, a metal foil, and an example of this metal foil is copper foil. The positive electrode current collector foil may be made of an electrically conductive resin. The positive electrode current collector foil is joined to a positive electrode tab (not shown).

[0014] The holding mechanism 20a compresses the stack 10a in the stacking direction (X-axis direction) to hold the surface pressure applied to the stack 10a. Specifically, the holding mechanism 20a compresses the stack 10a so that a surface pressure equal to or greater than a predetermined value is maintained. The holding mechanism 20a includes a surface pressure holding unit 21a, a hydraulic actuator 22a, and a hydraulic pump 40. Details of each component of the holding mechanism 20a will be described later. In this embodiment, the direction in the stacking direction (X-axis direction) where the surface pressure holding unit 21a and the hydraulic actuator 22a are located relative to the stack 10a is defined as downward, and the direction opposite to downward relative to the stack 10a is defined as upward. That is, in FIG. 1, the +X-axis direction is upward, and the −X-axis direction is downward.

[0015] The exterior member 30a is a member having a substantially rectangular parallelepiped shape, and houses the stack 10a, the surface pressure retaining unit 21a, and the hydraulically actuated unit 22a inside. The exterior member 30a is not particularly limited, but may be, for example, a metal case. The exterior member 30a has an inner upper surface 31 and an inner lower surface 32. The upper surface 31 and the lower surface 32 face each other in the stacking direction.

[0016] The laminate 10a has an upper surface 11 and a lower surface 12 located opposite the upper surface 11. The laminate 10a is stored so that the upper surface 11 contacts the upper surface 31 inside the exterior member 30a. Inside the exterior member 30a, a surface pressure maintaining unit 21a and a hydraulically actuated unit 22a are stored below the laminate 10a, i.e., on the side of the lower surface 12 of the laminate 10a. The surface pressure maintaining unit 21a and the hydraulically actuated unit 22a overlap with the laminate 10a in the surface direction. For example, the surface pressure maintaining unit 21a and the hydraulically actuated unit 22a are arranged side by side in the surface direction (Y-axis direction). The upper surface 211 of the surface pressure maintaining unit 21a faces the lower surface 12 of the laminate 10a, and the lower surface 212 contacts the lower surface 32 inside the exterior member 30a. The hydraulic actuator 22a has an upper surface 221 facing the lower surface 12 of the stack 10a, and a lower surface 222 in contact with the inner lower surface 32 of the exterior member 30a. That is, the upper surface 211 of the surface pressure retaining unit 21a faces a portion of the lower surface 12 of the stack 10a and applies surface pressure to the lower surface 12 of the stack 10a. The upper surface 221 of the hydraulic actuator 22a faces another portion of the lower surface 12 of the stack 10a and applies surface pressure to the lower surface 12 of the stack 10a. The upper surfaces 211 and 221 are, for example, the surfaces of an abutting plate that abuts against the stack 10a, which come into surface contact with the lower surface 12 of the stack 10a. In this embodiment, the surface pressure retaining unit 21a and the hydraulic actuating unit 22a are not limited to being arranged side by side in the surface direction (Y-axis direction) as long as the surface pressure retaining unit 21a and the hydraulic actuating unit 22a are positioned in the expansion / contraction direction of the laminate 10a and can retain the surface pressure of the laminate 10a. For example, as will be described later, the surface pressure retaining unit 21a and the hydraulic actuating unit 22a may be arranged side by side in the stacking direction (X-axis direction).

[0017] The stack 10a is compressed in the stacking direction by the holding mechanism 20a and stored inside the exterior member 30a. In this embodiment, the holding mechanism 20a holds the surface pressure of the stack 10a using the surface pressure holding unit 21a and the hydraulic actuator 22. Note that the state of holding the surface pressure of the stack 10a includes, for example, a state in which the stack 10a is subjected to a load generated by the stack 10a. The surface pressure holding unit 21a holds the surface pressure of the stack 10a by hydraulic pressure in response to fluctuations in the load in the stacking direction due to expansion and contraction of the stack 10a. That is, the surface pressure holding unit 21a passively holds the surface pressure of the stack 10a. For example, the surface pressure holding unit 21a holds the surface pressure of the stack 10a when the stack 10a is expanding or when the stack 10a is not expanding or contracting. The surface pressure holding unit 21a includes, for example, a hydraulic cylinder mechanism. The hydraulic cylinder mechanism has a highly airtight hydraulic chamber and can maintain a constant high hydraulic pressure. Therefore, even if high pressure acts on the surface pressure holding unit 21a due to the reaction force of the stack 10a compressed by the hydraulic actuator 22, the surface pressure holding unit 21a can hold the surface pressure of the stack 10a using a small-diameter hydraulic cylinder mechanism.

[0018] The surface pressure maintaining unit 21a adjusts the hydraulic pressure in the hydraulic chamber. This hydraulic pressure is for maintaining the surface pressure of the laminated body 10a and is also referred to as the maintained hydraulic pressure. Adjusting the maintained hydraulic pressure varies the load that the surface pressure maintaining unit 21a applies to the laminated body 10a. The higher the maintained hydraulic pressure, the greater the compressive load that the surface pressure maintaining unit 21a applies to the laminated body 10a. In this embodiment, the surface pressure maintaining unit 21a adjusts the maintained hydraulic pressure according to the state of the vehicle. Specifically, when the vehicle is stopped, the surface pressure maintaining unit 21 adjusts the maintained hydraulic pressure to the maximum maintained hydraulic pressure. The maximum maintained hydraulic pressure is the maximum value of the maintained hydraulic pressure that can be applied by the surface pressure maintaining unit 21a. Furthermore, when the vehicle is moving, the surface pressure maintaining unit 21 adjusts the maintained hydraulic pressure to zero.

[0019] Here, a specific example of the surface pressure holding unit 21a will be described using FIG. 2. FIG. 2 is a diagram illustrating an example of a surface pressure holding unit provided in the holding mechanism according to this embodiment. The XY axes in FIG. 2 correspond to the XY axes in FIG. 1. As shown in the example of FIG. 2, the surface pressure holding unit 21a is a hydraulic cylinder mechanism that holds the surface pressure of the stack 10a against a load applied downward from the stack 10a located above the hydraulic cylinder mechanism. The hydraulic cylinder mechanism includes a hydraulic chamber 201 filled with oil, a hydraulic piston 202 movable in the stacking direction within the hydraulic chamber 201, and an abutment plate 203 that abuts against the lower surface 12 of the stack 10a. The hydraulic piston 202 and the abutment plate 203 are connected by a rod. The surface of the abutment plate 203 that abuts against the lower surface 12 of the stack 10a corresponds to the upper surface 211 of the surface pressure holding unit 21a shown in FIG. 1. A compression spring may be provided inside the hydraulic chamber 201, connecting the hydraulic piston to the bottom of the hydraulic chamber and extending in the stacking direction.

[0020] Furthermore, the surface pressure maintaining unit 21a may be provided with a check valve 204. The check valve 204 opens in a direction to supply oil into the hydraulic chamber 201 of the surface pressure maintaining unit 21a and closes in a direction to discharge oil from the hydraulic chamber 201. When the laminate 10a expands, the surface pressure maintaining unit 21a closes the check valve 204 to seal the hydraulic chamber 201 and maintain the surface pressure applied to the laminate 10a. When the laminate 10a contracts, the hydraulic operating unit 22a operates to compress the laminate 10a, so that the check valve 204 opens without receiving a reaction force from the laminate 10a, and oil is supplied to the hydraulic chamber 201 in accordance with the contraction of the laminate 10a, while the position of the abutment plate 203 in the stacking direction moves upward (in the contraction direction of the laminate 10a).

[0021] The surface pressure retaining unit 21a may also include an oil passage 205 that adjusts the oil pressure in the hydraulic chamber 201. The oil passage 205 includes an oil pressure adjustment valve 206, and when the oil pressure becomes excessive due to expansion of the laminated body 10a, the oil pressure is maintained constant by releasing the oil pressure through the oil pressure adjustment valve 206. Alternatively, for example, the oil pressure adjustment valve 206 may be formed by providing a gap between the side wall of the hydraulic chamber 201 and the hydraulic piston 202. When the oil pressure is low, oil leakage from the gap is reduced, so the oil pressure is maintained constant. When the oil pressure is high, oil leakage from the gap increases, so the increase in oil pressure is suppressed. By using the gap between the side wall of the hydraulic chamber 201 and the hydraulic piston 202 as the oil pressure adjustment valve, there is no need to provide a separate oil passage outside the hydraulic cylinder mechanism, which allows for miniaturization and cost reduction.

[0022] The hydraulic actuating unit 22a operates by hydraulic pressure to apply a load to the stack 10a in the stacking direction. That is, the hydraulic actuating unit 22a actively maintains the surface pressure of the stack 10a. For example, when the stack 10a is contracted, the hydraulic actuating unit 22a applies a compressive load to the stack 10a to maintain the surface pressure of the stack 10a. The hydraulic actuating unit 22a is connected to a hydraulic pump 40 via hydraulic piping 41. The hydraulic pump 40 supplies hydraulic pressure to the hydraulic actuating unit 22a via the hydraulic piping 41. The hydraulic pressure is hydraulic pressure for operating the hydraulic actuating unit 22a and is also referred to as operating hydraulic pressure. The higher the operating hydraulic pressure, the greater the compressive load that the hydraulic actuating unit 22a applies to the stack 10a. The hydraulic actuating unit 22a includes, for example, a hydraulic actuator including a reducer and a hydraulic motor. The hydraulic actuating unit 22a operates to apply a large load to the stack 10a with a small hydraulic pressure by generating torque using a hydraulic motor based on hydraulic pressure supplied from the hydraulic pump 40 and amplifying the torque using a reducer. This allows the hydraulic pump and hydraulic motor to be made smaller. For example, the hydraulic actuating unit 2a applies a compressive load to the stack 10a by pushing upward an abutment plate that is in surface contact with the lower surface 12 of the stack 10a using torque generated based on hydraulic pressure supplied from the hydraulic pump 40. The surface of the abutment plate that is in surface contact with the lower surface 12 of the stack 10a corresponds to the upper surface 221 of the hydraulic actuating unit 22a shown in FIG. 1.

[0023] In this embodiment, the hydraulic actuating unit 22a adjusts the hydraulic pressure according to the state of the vehicle. Specifically, when the vehicle is stopped, the hydraulic actuating unit 22a adjusts the hydraulic pressure to zero. When the vehicle is moving, the hydraulic actuating unit 22a adjusts the hydraulic pressure to the maximum hydraulic pressure. The maximum hydraulic pressure is the maximum value of the hydraulic pressure that can be applied to the hydraulic actuating unit 22a.

[0024] Furthermore, in this embodiment, the operation method of the surface pressure maintaining unit 21a and the hydraulically operated unit 22a when the vehicle is traveling is not limited to the above-described method, and other methods may also be used. An example of the operation method of the surface pressure maintaining unit 21a and the hydraulically operated unit 22a when the vehicle is traveling will be described below. When the vehicle is traveling, the following two situations are assumed. There are situations in which power consumption is high and the contraction rate of the laminate 10a is high, and situations in which power consumption is low or zero and the contraction rate of the laminate 10a is low or zero. In situations in which power consumption is high and the contraction rate of the laminate 10a is high, the hydraulically operated unit 22a operates to apply a compressive load to the laminate 10a, thereby maintaining the surface pressure of the laminate 10a. In situations in which power consumption is low or zero and the contraction rate of the laminate 10a is low or zero, the hydraulically operated unit 22a initially operates to apply a compressive load to the laminate 10a, thereby maintaining the surface pressure of the laminate 10a, and then, in the latter half, the surface pressure maintaining unit 21a maintains the surface pressure of the laminate 10a. If the vehicle is traveling for a short period of time, the vehicle may stop before the part that maintains the surface pressure of the laminate 10a switches from the hydraulically actuated part 22a to the surface pressure maintaining part 21a.

[0025] Below, we will explain how the surface pressure maintaining unit 21 and the hydraulically actuated unit 22 operate when power consumption is low or zero and the contraction rate of the stack 10a is low or zero. Specifically, first, the hydraulically actuated unit 22a compresses the stack 10a with a load greater than the maximum load of the surface pressure maintaining unit 21a. As a result, the position of the lower surface 12 of the stack 10a in the stacking direction moves upward (in the contraction direction). The surface pressure maintaining unit 21a moves the position of the upper surface 211 upward so as to follow the position of the lower surface 12 of the stack 10a moved by the hydraulically actuated unit 22a. Next, the hydraulically actuated unit 22a reduces the operating oil pressure, thereby reducing the load applied to the stack 10a. As a result, the stack 10a expands due to the reaction force of the compression exerted by the hydraulically actuated unit 22a. Furthermore, the part that maintains the surface pressure of the stack 10a switches from the hydraulically actuated unit 22a to the surface pressure maintaining unit 21a. The surface pressure retaining portion 21a contracts slightly due to the load applied by the expanding stack 10a, compressing the oil in the hydraulic chamber, generating high hydraulic pressure in the hydraulic chamber, thereby allowing the surface pressure retaining portion 21a to retain the surface pressure of the stack 10a.

[0026] In this embodiment, by providing both the surface pressure retaining unit 21 and the hydraulic actuating unit 22, the surface pressure of the stack 10 can be reliably maintained while the vehicle is stopped, while reducing the hydraulic pressure generated by the hydraulic pump 40, which is the drive source. Furthermore, because the actuating hydraulic pressure can be reduced, the hydraulic pump 40 and hydraulic motor can be made smaller, and the pressure resistance of the hydraulic piping 41 can be reduced, resulting in a reduction in the size and weight of the hydraulic piping 41. Furthermore, because the surface pressure retaining unit 21 can increase the hydraulic pressure in the hydraulic chamber of the hydraulic cylinder mechanism, the surface pressure of the stack 10 can be maintained without increasing the cylinder diameter.

[0027] In this embodiment, when there are multiple stacks 10, each stack 10 is provided with a surface pressure retaining unit 21 and a hydraulic actuation unit 22. In the example of FIG. 1, in addition to the battery module 1a including the stack 10, there are also a battery module 1b including a stack 10b and a battery module 1c including a stack 10c. In the battery module 1b, the stack 10b is provided with a surface pressure retaining unit 21b and a hydraulic actuation unit 22b. In the battery module 1c, the stack 10c is provided with a surface pressure retaining unit 21c and a hydraulic actuation unit 22c. The hydraulic actuation units (22a, 22b, 22c) provided in each of the multiple stacks (10a, 10b, 10c) are operated by a single hydraulic pump 40. Specifically, as shown in FIG. 1, the hydraulic pump 40 supplies hydraulic pressure to each of the hydraulic actuation units 22a, 22b, 22c. This eliminates the need to provide a drive source for each battery module, even when there are multiple battery modules, allowing the holding mechanism to be made smaller.

[0028] In this embodiment, the adjustment of the hydraulic pressure of the surface pressure maintaining unit 21 and the hydraulic actuation unit 22 may be controlled by a controller (not shown). The controller is composed of a memory such as a ROM or a RAM, and a processor such as a CPU. The controller acquires, for example, the state of the vehicle or the state of the laminated body 10, and controls the hydraulic pressure of the surface pressure maintaining unit 21 and the hydraulic actuation unit 22 according to the state of the vehicle or the state of the laminated body 10. The state of the laminated body 10 includes the state of expansion and contraction of the laminated body 10 or the state of the surface pressure of the laminated body 10. The surface pressure maintaining unit 21 and the hydraulic actuation unit 22 adjust the hydraulic pressure according to commands from the controller. The controller may control the surface pressure maintaining unit 21 and the hydraulic actuation unit 22 collectively, or may be provided for each of the surface pressure maintaining unit 21 and the hydraulic actuation unit 22 and control them separately.

[0029] Here, an example of a method for maintaining the surface pressure of the stack 10 using the retention mechanism 20 will be described with reference to FIG. 3. FIG. 3 is a diagram illustrating changes in the state of the stack and retention mechanism according to the state of the vehicle in this embodiment. FIG. 3 shows a graph with time on the horizontal axis and the battery charge rate on the vertical axis, a graph with time on the horizontal axis and the thickness of the stack, a graph with time on the horizontal axis and the thickness of the stack, a graph with time on the horizontal axis and the load applied to the stack from the retention mechanism on the vertical axis, and a graph with time on the horizontal axis and the hydraulic pressure of the retention mechanism. The graph with load on the vertical axis shows the load of the surface pressure retention unit and the load of the hydraulically actuated unit. The graph with hydraulic pressure on the vertical axis shows the maintained hydraulic pressure of the surface pressure retention unit and the hydraulically actuated unit. As shown in FIG. 3, the battery charge rate is maintained at a constant value during a vehicle stop period P1 in which a vehicle equipped with a battery as a battery is stopped because no charging or discharging occurs. During period P1, the battery charge rate does not change, and the thickness of the stack 10 is also maintained at a constant value. During the vehicle stop period P1, the surface pressure maintaining unit 21 maintains the surface pressure applied to the stacked body 10. Specifically, as shown in FIG. 3, the surface pressure maintaining unit 21 adjusts the maintained hydraulic pressure to a maximum maintained hydraulic pressure H1 and applies the maximum load L1 of the surface pressure maintaining unit 21 to the stacked body 10. At this time, the operating hydraulic pressure of the hydraulic operating unit 22 is adjusted to zero. As a result, the load applied by the hydraulic operating unit 22 to the stacked body 10 also becomes zero.

[0030] Furthermore, at time T1, the vehicle starts and begins to run. During a vehicle running period P2 while the vehicle is running, the battery discharges, and the battery's charging rate decreases. At this time, the laminate 10 contracts, and the thickness of the laminate 10 decreases. During period P2, the surface pressure maintaining unit 21 adjusts the maintained oil pressure to zero. As a result, the load applied by the surface pressure maintaining unit 21 to the laminate 10 becomes zero. Furthermore, the hydraulic operating unit 22 adjusts the operating oil pressure to a maximum operating oil pressure H2, and applies a maximum load L2 of the hydraulic operating unit 22 to the laminate 10. The maximum operating oil pressure H2 is a value smaller than the maximum maintained oil pressure H1. As a result, the load caused by increasing the operating oil pressure of the hydraulic operating unit 22 can be reduced. Furthermore, the maximum load L2 applied by the hydraulic operating unit 22 to the laminate 10 is greater than the maximum load L1 applied by the surface pressure maintaining unit 21 to the laminate 10. The hydraulic actuating unit 22 can apply a load that is greater than the load that the surface pressure maintaining unit 21 can apply to the laminate 10, at an actuating oil pressure that is smaller than the maintaining oil pressure applied to the surface pressure maintaining unit 21. As a result, when the hydraulic actuating unit 22 compresses the laminate 10 and then the surface pressure maintaining unit 21 shifts to maintaining the surface pressure of the laminate 10, the holding force of the surface pressure maintaining unit 21 is balanced at a surface pressure that is smaller than the surface pressure maintained by the hydraulic actuating unit 22. In other words, by making the compressive load by the hydraulic actuating unit 22 greater than the compressive load by the surface pressure maintaining unit 21, the surface pressure maintaining unit 21 can maintain the holding force when holding the laminate 10 at a position where the loads are balanced, at the required holding force.

[0031] Furthermore, the traveling vehicle stops at time T2. A vehicle stop period P3 during which the vehicle is stopped includes a charging period P4 during which the battery is charged. During the period P3 during which the battery is not being charged, the battery's charging rate is again maintained at a constant value. Specifically, from the time the vehicle stops (time T2) to the time charging starts (time T3), the charging rate at which the vehicle was stopped (time T2) is maintained. At this time, the thickness of the laminate 10 remains unchanged and maintained at a constant value. When the battery starts charging from time T3, the battery's charging rate increases during charging period P4. During period P4, the thickness of the laminate 10 increases. When battery charging ends at time T4, the battery's charging rate and the thickness of the laminate 10 are again maintained at constant values.

[0032] During period P3, the hydraulic actuator 22 adjusts the hydraulic pressure to zero. As a result, the load applied to the stack 10 by the hydraulic actuator 22 becomes zero. Furthermore, the surface pressure maintaining unit 21 adjusts the maintaining hydraulic pressure to the maximum maintaining hydraulic pressure H1 and applies the maximum load L1 of the surface pressure maintaining unit 21 to the stack 10. As described above, the hydraulic pressure for operating the hydraulic actuator 22 while the surface pressure maintaining unit 21 is maintaining the surface pressure is lower than the hydraulic pressure for operating the hydraulic actuator 22 while the surface pressure maintaining unit 21 is not maintaining the surface pressure. As a result, while the surface pressure maintaining unit 21 is maintaining the stack 10, the surface pressure of the stack 10 can be maintained even if the hydraulic pressure of the hydraulic actuator 22 is reduced, thereby reducing energy consumption by reducing the hydraulic pressure. Furthermore, since the hydraulic actuator 22 needs to operate so as to apply a load in the compressive direction to the surface pressure of the stack 10, increasing the hydraulic pressure during operation of the hydraulic actuator 22 ensures reliable operation of the hydraulic actuator 22. For example, a scene in which the hydraulic actuating unit 22 holds the laminate 10 and the surface pressure holding unit 21 does not hold the laminate 10 includes a scene in which the hydraulic actuating unit 22 extends its stroke in response to contraction of the laminate 10 to apply surface pressure to the laminate 10, and a scene in which the laminate 10 does not expand or contract but the surface pressure of the laminate 10 is low, so the hydraulic actuating unit 22 extends its stroke to increase the surface pressure applied to the laminate 10. Note that in this embodiment, the part that holds the surface pressure of the laminate 10 is switched to either the surface pressure holding unit 21 or the hydraulic actuating unit 22, but this is not limiting, and there may be a period in which the surface pressure of the laminate 10 is held by both the surface pressure holding unit 21 and the hydraulic actuating unit 22.

[0033] <<Example 1>> Next, an example of a holding mechanism according to an embodiment of the present invention will be described. FIG. 4 is a top view and a cross-sectional view schematically illustrating an example of a holding mechanism according to this embodiment. The XYZ axes in FIG. 4 correspond to the XY axes in FIG. 1. The Y and Z axes are directions along the top surface of the laminate 10. The Z axis is perpendicular to the Y axis in the YZ plane. The upper view in FIG. 4 is a top view, and the lower view in FIG. 4 is a cross-sectional view. The top view and cross-sectional view on the left side of FIG. 4 show an example of the holding mechanism 20 when the laminate 10 is contracted. That is, the stroke amount of the hydraulic cylinder of the surface pressure retaining unit 21 is maximum when the laminate 10 is at its maximum contraction. The top view and cross-sectional view on the right side of FIG. 4 show an example of the holding mechanism 20 when the laminate 10 is expanded. That is, the stroke amount of the hydraulic cylinder of the surface pressure retaining unit 21 is minimum when the laminate 10 is at its maximum expansion. The top view is a top view of the holding mechanism 20, with the stack 10, the upper surface 31 of the exterior member 30, and the abutment plate 231 omitted. The cross-sectional view is a cross-sectional view of the holding mechanism taken along line AA' in the top view. As shown in FIG. 4, in Example 1, the surface pressure holding unit 21 and the hydraulically actuated unit 22 are disposed in the center 101 of the stack 10 when viewed from the stacking direction. As shown in the cross-sectional view of FIG. 4, the surface pressure holding unit 21 is disposed between the stack 10 and the hydraulically actuated unit 22 in the stacking direction.

[0034] The surface pressure retaining unit 21 includes a retaining portion 238, which is a cylindrical member, and a hydraulic chamber 230 located within the retaining portion 238. The hydraulic chamber 230 is sealed by a contact plate 231, one end of which contacts the stack 10. The hydraulic chamber 230 supports the contact plate 231 by adjusting the hydraulic pressure. The surface pressure retaining unit 21 retains the surface pressure of the stack 10 via the contact plate 231. The hydraulic actuating unit 22 uses hydraulic pressure supplied from the hydraulic pump 40 as a power source to rotate a motor shaft 233 of a hydraulic motor 232 to generate torque. The motor shaft 233 is connected to an input shaft 235 of a reducer 234. The torque generated by the hydraulic motor 232 is transmitted to the reducer 234 via the input shaft 235. The reducer 234 includes an output portion 237 (elastic gear) on a fixed portion 236, which is connected to the retaining portion 238. The torque transmitted to the input shaft 235 is amplified by the reducer 234 and acts to support the holding portion 238 .

[0035] Here, the hydraulic motor 232 provided in the hydraulic actuation unit 22 according to this embodiment will be described with reference to FIG. 5. FIG. 5 is a top view, a cross-sectional view, and a bottom view showing an example of a hydraulic motor provided in the hydraulic actuation unit according to this embodiment. The cross-sectional view is a cross-sectional view taken along line BB' of the hydraulic motor 232 shown in the top view. As shown in the bottom view, in the hydraulic motor 232, oil is supplied from an oil supply port 239 provided on the bottom surface of the hydraulic motor 232 and discharged from an oil discharge port 240 provided on the bottom surface. In FIG. 5, the flow of oil is indicated by arrows. Oil is supplied from the hydraulic pump 40 to the oil supply port 239. The oil is discharged from the oil discharge port 240 toward the hydraulic pump. In the hydraulic motor 232, as shown in the top view, the motor shaft 233 rotates due to the circulation of oil passing through an oil chamber 241.

[0036] <<Example 2>> Next, an example of an embodiment of a holding mechanism according to the present invention will be described. FIG. 6 shows a top view and a cross-sectional view of an embodiment of the holding mechanism according to the present invention. The XYZ axes in FIG. 6 correspond to those in FIG. 1. The Y and Z axes are oriented along the top surface of the laminate 10. The Z axis is perpendicular to the Y axis in the YZ plane. The upper view in FIG. 6 is a top view, and the lower view is a cross-sectional view. The top view and cross-sectional view on the left side of FIG. 6 show an embodiment of the holding mechanism 20 when the laminate 10 is contracted. That is, the stroke amount of the hydraulic cylinder of the surface pressure retaining unit 21 is maximized when the laminate 10 is fully contracted. The top view and cross-sectional view on the right side of FIG. 6 show an embodiment of the holding mechanism 20 when the laminate 10 is expanded. That is, the stroke amount of the hydraulic cylinder of the surface pressure retaining unit 21 is minimized when the laminate 10 is fully expanded. Note that the top view is a top view of the holding mechanism 20, with the laminate 10, the upper surface 31 of the exterior member 30, and the abutment plate 231 omitted. The cross-sectional view is a cross-sectional view of the holding mechanism taken along line CC' in the top view. As shown in Fig. 4, in Example 2, the two surface pressure holding units 21 and the hydraulic actuating unit 22 are arranged so as to be aligned along the surface direction (Y-axis direction) when viewed from the stacking direction. The hydraulic actuating unit 22 is arranged in the center of the stack 10 so as to be sandwiched between the two surface pressure holding units 21 when viewed from the stacking direction.

[0037] The surface pressure retaining unit 21 includes a side wall 230a, which is a cylindrical member with a bottom, and a retaining portion 238a, which is also a cylindrical member with a bottom. The retaining portion 238a is slidably disposed within the side wall 230a along the inner side surface of the side wall 230a. The hydraulic chamber 230 is a space sealed by the side wall 230a and the retaining portion 238a. The retaining portion 238a is a member that retains the contact plate 231. The surface pressure retaining unit 21 supports the contact plate 231 via the retaining portion 238a by adjusting the hydraulic pressure in the hydraulic chamber 230. Furthermore, the hydraulic actuating unit 22 uses hydraulic pressure supplied from the hydraulic pump 40 as a power source to rotate the motor shaft 233 of the hydraulic motor 232 to generate torque. The torque generated by the hydraulic motor 232 supports the retaining portion 238b via the reducer 234. The specific method is similar to the example in FIGS. 4 and 5, so a detailed description thereof will be omitted and the descriptions of FIGS. 4 and 5 will be used as appropriate.

[0038] As described above, the retention mechanism according to this embodiment is a retention mechanism that compresses the all-solid-state battery stack in the stacking direction to retain the surface pressure applied to the stack, and includes a surface pressure retention unit that retains the surface pressure by hydraulic pressure in response to fluctuations in the load in the stacking direction due to expansion and contraction of the stack, a hydraulic actuation unit that operates by hydraulic pressure to apply a load to the stack in the stacking direction, and a hydraulic pump that supplies hydraulic pressure to the hydraulic actuation unit, wherein the maximum operating hydraulic pressure for operating the hydraulic actuation unit is lower than the maximum retained hydraulic pressure for maintaining the surface pressure of the surface pressure retention unit. This makes it possible to more appropriately retain the surface pressure applied to the stack in response to fluctuations in the load due to expansion and contraction of the all-solid-state battery stack.

[0039] Furthermore, in the retention mechanism according to this embodiment, the hydraulic pressure for operating the hydraulically actuated unit when the surface pressure retention unit is maintaining the surface pressure is lower than the hydraulic pressure for operating the hydraulically actuated unit when the surface pressure retention unit is not maintaining the surface pressure. As a result, while the surface pressure is maintained by the surface pressure retention unit, the surface pressure can be maintained even if the hydraulic pressure of the hydraulically actuated unit is reduced, and therefore energy consumption can be reduced by reducing the hydraulic pressure.

[0040] Furthermore, in the holding mechanism according to this embodiment, the maximum load that the hydraulic actuator applies to the stack in the stacking direction is greater than the maximum load that the surface pressure holder applies to the stack in the stacking direction. As a result, when the surface pressure holder holds the surface pressure after compression by the hydraulic actuator, even if the position of the upper surface of the surface pressure holder drops due to the reaction force of compression by the hydraulic actuator, the required surface pressure can be maintained at a position that balances with the load from the stack.

[0041] Furthermore, in the holding mechanism according to this embodiment, the hydraulic actuation unit includes a hydraulic actuator that includes a reducer and a hydraulic motor. This allows a large load to be applied to the stack by the reducer even when a small hydraulic pressure is supplied, allowing the hydraulic pump and hydraulic motor to be made smaller.

[0042] In addition, in the holding mechanism according to this embodiment, the surface pressure holding unit includes a hydraulic cylinder mechanism, which increases the sealing performance of the hydraulic chamber by using the hydraulic cylinder and maintains a constant high hydraulic pressure, allowing the surface pressure to be maintained using a small-diameter hydraulic cylinder.

[0043] In addition, in the holding mechanism according to this embodiment, the surface pressure holding unit is provided with a check valve that opens in the direction of injecting oil into the hydraulic chamber of the hydraulic cylinder mechanism and closes in the direction of discharging oil from the hydraulic chamber of the hydraulic cylinder mechanism. This allows the surface pressure to be adjusted in accordance with the expansion and contraction of the laminate by opening and closing the check valve in response to the expansion and contraction of the laminate.

[0044] Furthermore, in the holding mechanism according to this embodiment, the surface pressure holding unit includes an oil passage that adjusts the oil pressure in the hydraulic chamber of the hydraulic cylinder mechanism. This allows the oil pressure to be released and maintained constant even if the oil pressure becomes excessive due to expansion of the laminate.

[0045] Furthermore, when the holding mechanism according to this embodiment has multiple stacks, each stack is provided with a surface pressure holding unit and a hydraulic actuation unit, and the hydraulic actuation units provided for each of the multiple stacks are operated by a single hydraulic pump. This allows the number of hydraulic pumps to be reduced, thereby making it possible to downsize the entire holding mechanism.

[0046] Furthermore, in the holding mechanism according to this embodiment, the surface pressure holding unit and the hydraulic actuating unit are disposed in the center of the stack when viewed from the stacking direction, which makes it possible to make the surface pressure of the stack uniform.

[0047] It should be noted that the above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above-described embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Explanation of symbols]

[0048] 1...Battery module 10...All-solid-state battery stack 20...holding mechanism 21…Surface pressure holding part 22...Hydraulic operating unit 40...Hydraulic pump 30...Exterior material

Claims

1. A holding mechanism that compresses a stack of an all-solid-state battery in a stacking direction and holds a surface pressure applied to the stack, a surface pressure holding unit that holds the surface pressure by hydraulic pressure in response to a change in load in the stacking direction due to expansion and contraction of the stack; a hydraulic actuating unit that operates by the hydraulic pressure to apply a load to the stack in the stacking direction; a hydraulic pump that supplies the hydraulic pressure to the hydraulic actuation unit, A holding mechanism in which a maximum operating hydraulic pressure for operating the hydraulic actuation unit is lower than a maximum holding hydraulic pressure for holding the surface pressure of the surface pressure holding unit.

2. 2. The retention mechanism of claim 1, A holding mechanism in which the operating oil pressure for operating the hydraulically operated unit when the surface pressure holding unit is holding the surface pressure is lower than the operating oil pressure for operating the hydraulically operated unit when the surface pressure holding unit is not holding the surface pressure.

3. 3. The holding mechanism according to claim 1 or 2, A holding mechanism in which the maximum load that the hydraulic operating unit applies to the stack in the stacking direction is greater than the maximum load that the surface pressure holding unit applies to the stack in the stacking direction.

4. 3. The holding mechanism according to claim 1 or 2, The hydraulically actuated portion is a holding mechanism including a hydraulic actuator having a reducer and a hydraulic motor.

5. 3. The holding mechanism according to claim 1 or 2, The surface pressure holding unit is a holding mechanism including a hydraulic cylinder mechanism.

6. 6. The retention mechanism according to claim 5, the surface pressure maintaining portion includes a check valve, The check valve is a holding mechanism that opens in a direction to inject oil into the hydraulic chamber of the hydraulic cylinder mechanism and closes in a direction to discharge the oil from the hydraulic chamber of the hydraulic cylinder mechanism.

7. 6. The retention mechanism according to claim 5, The surface pressure holding portion is a holding mechanism including an oil passage for adjusting the oil pressure in the hydraulic chamber of the hydraulic cylinder mechanism.

8. 3. The holding mechanism according to claim 1 or 2, When there are a plurality of the stacked bodies, each of the stacked bodies is provided with the surface pressure retaining unit and the hydraulic actuating unit, The hydraulic actuating unit provided in each of the plurality of stacks is a holding mechanism actuated by one of the hydraulic pumps.

9. 3. The holding mechanism according to claim 1 or 2, A holding mechanism in which the surface pressure holding unit and the hydraulic operating unit are arranged in the center of the stack when viewed from the stacking direction.

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