Vehicle battery unit control device

Abstract

To suppress progress of high-rate deterioration of a battery cell during a continuous charge and discharge of a large current.SOLUTION: A battery unit 110 comprises: a battery module 60 in which a plurality of battery cells 62 and a plurality of plates 63 are alternately overlapped and bound in an overlapping direction; and a binding load variable mechanism 80 that changes a binding load applied to each battery cell 62. Each plate 63 includes a contact part 63a and a concave part 91 on a face directed to each battery cell. By increasing the binding load applied to each battery cell at a charge and discharge of a large current, a strong pressure force is applied to the battery cell 62 from the contact part 63a. Thus, the movement of an electrolyte at a portion corresponding to the concave part 91 in the battery cell 62 is suppressed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vehicle battery unit control device. [Background technology]

[0002] It is known that rechargeable battery cells used in electric and hybrid vehicles experience a temporary (reversible) increase in the battery's internal resistance (so-called "high-rate degradation") when they are continuously charged and discharged at a large current. Although the degradation will recover when charging and discharging are stopped, the longer the high-current charging and discharging time, the more the battery cell deteriorates, so it takes time for the battery to recover after charging and discharging are stopped.

[0003] Patent document 1 describes that the amount of high-rate degradation is calculated based on the electrical resistance measured after the secondary battery has been in a state where charging and discharging have been stopped for a predetermined period of time or more, and the battery resistance measured when the secondary battery is in a state where it can be charged and discharged, and that when the amount of high-rate degradation exceeds a predetermined value (high-rate degradation has not recovered), charging and discharging of the secondary battery is restricted. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-32966 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to suppress the progression of high-rate deterioration of a battery cell during continuous large-current charging and discharging. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention is designed to suppress the movement of electrolyte in a battery cell during large current charging and discharging.

[0007] The vehicle battery unit control device disclosed herein is a control device for a battery unit configured by connecting a plurality of chargeable and dischargeable battery cells in series, the battery unit includes a battery module in which the plurality of battery cells and a plurality of plates are alternately stacked and constrained in the stacking direction, and a constraint load variable mechanism that changes the constraint load applied to each battery cell via the plates on both sides of the battery cell, the plate, which is disposed on at least one side of each battery cell, has, on a surface facing the battery cell, a contact portion that contacts the battery cell by the restraint load and applies a pressing force to the battery cell to suppress movement of the electrolyte in the battery cell toward the end of the battery cell, and a recess that is recessed relatively compared to the contact portion; The battery module is characterized by having a restraint load control unit that operates the restraint load variable mechanism so that the restraint load applied to the battery cell is larger during large current charging / discharging of the battery module that is equal to or greater than a predetermined current value than during small current charging / discharging that is less than the predetermined current value.

[0008] High-rate degradation occurs during large-current charging and discharging because the expansion and contraction of the negative electrode active material and the volumetric expansion of the electrolyte due to the insertion and desorption of ions in the electrolyte cause the electrolyte to flow out of the negative electrode active material layer and move toward the edges of the battery cell, resulting in uneven electrolyte distribution within the battery cell. This uneven distribution reduces the area where battery reactions occur and increases the internal resistance of the battery cell. This uneven electrolyte distribution is resolved by pausing charging and discharging.

[0009] According to the vehicle battery unit control device, each battery cell receives a restraint load via the plate in the overlapping direction of the battery cells. The plate, located on at least one side of each battery cell, has a contact portion that contacts the battery cell and a relatively recessed portion. Therefore, when the restraint load applied to the battery cell increases during high-current charging and discharging, a strong pressing force is applied to the battery cell from the contact portion of the plate. The electrolyte in the battery cell is less likely to move in the area where this strong pressing force is applied. Meanwhile, the pressing force applied to the battery cell from the recess of the plate is weak, or no pressing force is applied from the recess. Therefore, the electrolyte in the battery cell at the portion corresponding to the recess of the plate is prevented from moving toward the end of the battery cell in the area where the pressing force is applied from the contact portion of the battery cell. This prevents the electrolyte from becoming unevenly distributed due to continued high-current charging and discharging. In other words, the progression of high-rate degradation is suppressed.

[0010] In one embodiment, the restraint load control unit operates the restraint load variable mechanism during a charge / discharge pause when the battery module is not charging or discharging, so that the restraint load applied to the battery cell is smaller than during the low-current charge / discharge.

[0011] By reducing the restraining load on the battery cell, the pressing force applied to the battery cell from the plate abutment area is weakened, which makes it easier for the electrolyte to move within the battery cell, eliminating uneven electrolyte distribution and speeding up recovery from high-rate degradation.

[0012] In one embodiment, the battery cell is a wound type battery cell in which a positive electrode sheet and a negative electrode sheet are wound and flattened in a state insulated from each other via a sheet-like separator, and the electrode wound body is housed in a battery case together with an electrolyte solution, The plate disposed on at least one side of each battery cell has a plurality of slits extending in a direction perpendicular to the winding axis direction of the electrode winding body and arranged at intervals in the winding axis direction, and the base surface of the plate where the slits open is in contact with the electrode pond The contact portion contacts the cell, and each of the plurality of slits constitutes the recess.

[0013] In wound-type battery cells, electrolyte migrates to both ends of the winding axis of the electrode winding body due to continued high-current charging and discharging. Therefore, the plate is configured with multiple slits extending perpendicular to the winding axis and spaced apart along the winding axis. In this case, the portions between adjacent slits on the base surface, which form the abutment portions of the plate, also extend perpendicular to the winding axis. Therefore, the abutment portions prevent the electrolyte in the battery cell from migrating to both ends of the winding axis. Furthermore, the provision of multiple slits in the plate, which provides abutment portions and recesses, facilitates weight reduction and plate thickness reduction, which is advantageous for making the battery module lighter and more compact.

[0014] In one embodiment, the battery cell is wound as in the immediately preceding embodiment; The plate arranged on at least one side of each battery cell has a plurality of ribs extending in a direction perpendicular to the winding axis direction of the electrode winding body and arranged at intervals in the winding axis direction, and each of the plurality of ribs is pond The contact portion contacts the cell, and the recess is formed between the plurality of ribs.

[0015] In this embodiment, the plate is configured with a plurality of ribs extending perpendicular to the winding axis and spaced apart along the winding axis, thereby providing abutment portions and recesses. Therefore, the abutment portions, which are made of ribs, prevent the electrolyte in the battery cells from migrating to both ends along the winding axis due to continued high-current charging and discharging. The ribbed plate of this embodiment makes it easy to ensure rigidity with the ribs, and also provides a better function of separating adjacent battery cells than the plate with slits described above, which is advantageous for preventing the spread of fire among the battery cells.

[0016] In one embodiment, the pond The cell is a stacked type in which an electrode laminate, in which a plurality of positive electrode sheets and a plurality of negative electrode sheets are alternately stacked with separators interposed therebetween, is housed in a battery case together with an electrolyte; The plate disposed on at least one side of each battery cell has a plurality of through holes, and the base surface of the plate where the through holes are open is in contact with the battery cell. pond The through holes constitute the contact portion that contacts the cell, and each of the plurality of through holes constitutes the recess.

[0017] In stacked battery cells, electrolyte migrates to the periphery of the battery cell due to continued high-current charging and discharging. Therefore, the plates are configured with abutment portions and recesses formed by providing multiple through-holes. The migration of electrolyte in the areas of the battery cell corresponding to the through-holes (recesses) in the plates to the periphery of the battery cell is suppressed by the pressing force applied to the battery cell from the base surface (abutment portion) around the through-holes. Furthermore, because the abutment portions and recesses of the plates are formed by the through-holes, it is easy to reduce the weight and thickness of the plates, which is advantageous for making the battery module lighter and more compact.

[0018] In one embodiment, the pond The cells are stacked as in the immediately preceding embodiment, The plate disposed on at least one side of each battery cell has a plurality of blind holes, and the base surface of the plate where the blind holes are open is in contact with the battery cell. pond The contact portion contacts the cell, and each of the plurality of bottomed holes constitutes the recess.

[0019] This prevents the electrolyte in the battery cell at the portion corresponding to the hole (recess) in the plate from migrating to the periphery of the battery cell due to the pressing force applied to the battery cell from the base surface (contact portion) around the hole. In addition, the plate has a better function of separating adjacent battery cells than the plate with the through hole described above, which is advantageous in preventing the spread of fire. [Effects of the Invention]

[0020] According to the present invention, a contact portion and a recess are provided on a plate arranged on at least one side of each battery cell, and the restraining load applied to the battery cell during high-current charging and discharging is increased, so that a strong pressing force is applied to the battery cell from the contact portion. This suppresses the movement of electrolyte in the area of ​​the battery cell corresponding to the recess, thereby suppressing the progression of high-rate deterioration due to continued high-current charging and discharging. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a diagram showing the overall configuration of a hybrid vehicle equipped with a vehicle battery unit and its control device. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] 6 is a graph showing the characteristics of the limit integrated current amount depending on the battery temperature and the charge / discharge current value. [Figure 6] FIG. 10 is a graph showing the relationship between the high-rate degradation evaluation value and the charge / discharge rest time. [Figure 7] Control flow diagram when IG-ON. [Figure 8] FIG. 1 is a conceptual diagram showing the movement of the electrolyte solution as high-rate degradation progresses. [Figure 9] 6 is a graph showing the change in the resistance increase rate of a battery cell when charging and discharging at a large current and then pausing the charging and discharging. [Figure 10] Control flow diagram when IG-OFF. [Figure 11] FIG. 10 is a perspective view showing another example of a plate. [Figure 12] FIG. [Figure 13] FIG. 10 is a perspective view showing yet another example of a plate. [Figure 14] FIG. 10 is a side view, partly in cross section, showing a portion of a plate in yet another example. DETAILED DESCRIPTION OF THE INVENTION

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description of preferred embodiments is merely exemplary in nature and is not intended to limit the scope of the present invention, its applications, or uses.

[0023] This embodiment is an application of the present invention to a hybrid vehicle.

[0024] <Overall configuration of hybrid vehicle> As shown in FIG. 1, a hybrid vehicle 100 includes wheels 10, axles 12, an engine 20, a transmission 30, a motor 40, an inverter 50, a battery unit 110, and an electronic control unit (ECU) that controls the battery unit 110. ) 70. This hybrid vehicle 100 is a parallel type, and the engine 20 and the motor 40 function as a drive source that outputs driving force for the vehicle, and depending on the driving conditions, the vehicle can be driven by the engine 20 alone, by both the engine 20 and the motor 40, or by the motor 40 alone.

[0025] The engine 20 is connected to the axle 12 via a transmission 30. The engine 20 is, for example, a gasoline engine. The motor 40 is connected to the axle 12 and is connected to a battery module 60 of the battery unit 110 via an inverter 50. The electric power of the battery module 60 is converted into AC power by the inverter 50 and then supplied to the motor 40. The motor 40 functions as an electric motor upon receiving the supplied electric power and rotates the axle 12. The motor 40 also functions as a generator by performing regenerative operation when the hybrid vehicle 100 is decelerating, thereby charging the battery module 60.

[0026] <Battery unit> The battery unit 110 includes the battery module 60 and a variable constraint load mechanism 80. As shown in Fig. 2, the battery module 60 includes a plurality of chargeable and dischargeable battery cells 62, and the plurality of battery cells 62 and a plurality of plates 63 are alternately stacked in layers such that the plates 63 are disposed on both sides of each battery cell 62. Specifically, the plurality of battery cells 62 and the plurality of plates 63 are housed in a rectangular parallelepiped casing 61 in a state where they are stacked in a predetermined direction D (the horizontal direction in this embodiment). The variable constraint load mechanism 80 is provided between the plate 63 on one end side of the stacking direction D and a vertical wall on one end side of the casing 61.

[0027] The variable restraint load mechanism 80 varies the load that restrains the multiple battery cells 62 in the overlapping direction D, and is equipped with a pressure plate 81 and an actuator (electric cylinder) 82 that moves the pressure plate 81 back and forth in the overlapping direction D. The pressure plate 81 is fixed to the plate 63 on one end side of the overlapping direction D, and the restraint load applied to the multiple battery cells 62 changes depending on how the pressure plate 81 moves back and forth in the overlapping direction D. The actuator 82 is attached to a vertical wall on one end side of the casing 61.

[0028] As shown in Fig. 3, the battery cell 62 is formed by housing an electrode wound body 62a together with an electrolyte solution 62b in a battery case 65. The electrode wound body 62a is formed by winding and flattening a positive electrode sheet 66 and a negative electrode sheet 67 insulated from each other via a sheet-like separator 68. The electrode wound body 62a is housed in the battery case 65 with its winding axis direction A horizontal. Positive and negative electrode terminals 69 are provided on the upper surface of the battery cell 62.

[0029] The positive electrode sheet is made by mixing a positive electrode active material such as lithium cobalt oxide, a binder, and a conductive additive, and applying the mixture to a current collector such as aluminum foil. The negative electrode sheet is made by mixing a negative electrode active material such as graphite-based carbon material, a binder, and a conductive additive, and applying the mixture to a current collector such as copper foil. The separator 13 is made of polyethylene terephthalate (PEPC). The battery is made of a single-layer or multi-layer microporous film of a polyolefin such as polypropylene or polyethylene, and is impregnated with a non-aqueous electrolyte solution containing an organic compound as the main component. The non-aqueous electrolyte solution is made by dissolving a lithium salt (supporting electrolyte) in a non-aqueous solvent, and additives may be added as needed.

[0030] 4, the plate 63 has a plurality of slits 91 extending in a direction (vertical direction) perpendicular to the winding axis direction A of the electrode wound body 62a. The plurality of slits 91 are arranged side by side at intervals in the winding axis direction A.

[0031] When a restraint load is applied to a battery cell 62 by the restraint load variable mechanism 80, the slits 91 open and the base surface 63a of the plate 63 facing the battery cell 62 comes into strong contact with the battery cell 62. This base surface 63a forms the contact portion that applies a pressing force to the battery cell 62 due to the restraint load. The portion of the plate 63 where the slits 91 are located does not come into contact with the battery cell 62 even when a restraint load is applied to the battery cell 62 by the restraint load variable mechanism 80. The portion of the plate 63 where the slits 91 are located forms a recess that is recessed relatively from the base surface (contact portion) 63a. The plates 63 on both sides of each battery cell 62 have corresponding contact portions (base surfaces 63a) and recesses (slits 91).

[0032] <Battery unit control device> The battery unit 110 is controlled by a control device 70. As shown in Fig. 1, the control device 70 includes a current value determination unit 71 that determines whether charging and discharging of the battery module 60 is a large current charge and discharge, a degradation evaluation value calculation unit 72 that calculates a high-rate degradation evaluation value N of the battery module 60, a degradation evaluation value determination unit 73 that determines whether the battery cells 62 have recovered from high-rate degradation due to a pause in charging and discharging, and a constraint load control unit 74 that controls the operation of an actuator 82 of the constraint load variable mechanism 80.

[0033] The current value determination unit 71 acquires the charge / discharge current value I of the battery module 60 at predetermined sampling intervals (e.g., 0.1 to 1 second) while the IG-ON of the hybrid vehicle 100 is on (while the battery module 60 is charging / discharging as the hybrid vehicle 100 is being operated), and determines whether this charge / discharge current value I is equal to or greater than a preset current value Io (high current charge / discharge).

[0034] While the IG-ON state of the hybrid vehicle 100 (while the battery module 60 is being charged or discharged as the hybrid vehicle 100 is being driven) is in progress, the degradation evaluation value calculation unit 72 calculates, at predetermined time intervals (for example, every 10 seconds), a high-rate degradation evaluation value N (≦1) from the temperature of the battery module 60 (for example, the average temperature of the temperatures of the plurality of battery cells 62) and the charge / discharge current value I. The limit current integrated value Is is used for this calculation.

[0035] The limit integrated current value Is is obtained from the map shown in Figure 5 based on the battery temperature and the charge / discharge current value. Figure 5 shows the experimentally obtained relationship between the temperature of the battery module 60, the charge / discharge current value I, and the limit integrated current value Is. The limit integrated current value Is serves as a threshold value for determining whether or not to limit the charge / discharge current value I of the battery module 60 to a predetermined current value or less (prohibit large-current charge / discharge). If the integrated current value obtained by multiplying the charge / discharge current value I of the battery module 60 by the charge / discharge time is less than the limit integrated current value Is, this means that there is still some time before irreversible deterioration of the battery cells 62 occurs, and large-current charge / discharge is permitted.

[0036] When the battery module 60 is sufficiently rested and has recovered from high-rate degradation, the high-rate degradation evaluation value N is set to an initial value of 1. While the IG-ON state of the hybrid vehicle 100 is active, the charge / discharge current value is acquired every predetermined sampling period (for example, 0.1 to 1 second), and every predetermined unit time (for example, 10 seconds), a charge / discharge current value I, which is the average value of the acquired charge / discharge current values, is calculated. Then, the degradation evaluation value N is calculated and updated using the following formula based on the charge / discharge current value I (A) and the limit integrated current value Is (Ah). In the formula, 10s is the predetermined unit time. This is the unit time, and 3600s is equivalent to 1 hour (h).

[0037] This time, N value = previous N value - (I × 10 s / 3600 s) × I s Further, during the IG-OFF of the hybrid vehicle 100 (during the charge / discharge pause of the battery module 60 due to the operation stop of the hybrid vehicle 100), the degradation evaluation value calculation unit 72 calculates the high-rate degradation evaluation value N from the map shown in FIG. 6 based on the charge / discharge pause time tr of the battery module 60.

[0038] FIG. 6 is a graph showing the relationship between the pause time tr and the degradation evaluation value N, which is obtained by experiments. The degradation evaluation value N changes according to the pause time tr during which the charge / discharge is paused, and as the pause time of the charge / discharge becomes longer, the recovery of the high-rate degradation progresses, so the degradation evaluation value approaches 1. The characteristic line L1 shows the characteristics when the restraint load F applied to the battery cell 62 by the restraint load variable mechanism 80 is set to a small F3 described later, and the characteristic line L2 shows the characteristics when the restraint load F is set to an intermediate value F2. In the characteristic line L1, the degradation evaluation value N becomes 1.0 (complete recovery of the high-rate degradation) at a pause time slightly less than 7 hours from the point where the degradation evaluation value is 0, and in the characteristic line L2, the degradation evaluation value N becomes 1.0 when the pause time exceeds 11 hours from the point where the degradation evaluation value is 0.

[0039] The evaluation value determination unit 73 determines whether the degradation evaluation value N is less than 1 during the IG-OFF of the hybrid vehicle 100 (during the charge / discharge pause), that is, whether the high-rate degradation of the battery cell 62 has not reached complete recovery.

[0040] During the IG-ON of the hybrid vehicle 100 (during the charge / discharge), when the current value determination unit 71 determines that it is not during the high-current charge / discharge (I < Io), the restraint load control unit 74 controls the operation of the restraint load variable mechanism 80 so that the restraint load F applied to the battery cell 62 becomes the standard load F2. During the IG-ON, when the current value determination unit 71 determines that it is during the high-current charge / discharge (I ≥ Io), the restraint load control unit 74 controls the operation of the restraint load variable mechanism 80 so that the restraint load F applied to the battery cell 62 becomes the large load F1 (F1 > F2).

[0041] Further, when the evaluation value determination unit 73 determines that the degradation evaluation value N is less than 1 during IG-OFF (charging / discharging pause) of the hybrid vehicle 100, the restraint load control unit 74 controls the operation of the restraint load variable mechanism 80 so that the restraint load F applied to the battery cell becomes a small load F3 (F3 < F2). When the evaluation value determination unit 73 determines that the degradation evaluation value N has reached 1 even during IG-OFF (charging / discharging pause), the restraint load control unit 74 controls the operation of the restraint load variable mechanism 80 so that the restraint load F applied to the battery cell becomes the standard load F2.

[0042] (Control flow during IG-ON) The control flow during IG-ON is shown in FIG. 7. The control starts by turning on the ignition (IG-ON) of the hybrid vehicle 100. In step A1 after starting, the charge / discharge current value I of the battery module 60 is acquired. In the subsequent step A2, it is determined whether the charge / discharge current value I is equal to or greater than a predetermined current value Io. When I ≥ Io (during large current charge / discharge), the process proceeds to step A3, and the restraint load variable mechanism 80 is controlled so that the restraint load F applied to the battery cell 62 becomes the large load F1. On the other hand, when I < Io (not during large current discharge), the process proceeds to step A4, and the restraint load variable mechanism 80 is controlled so that the restraint load F becomes the standard load F2.

[0043] Here, as shown in FIG. 8, when large current charge / discharge continues, initially (A), the entire electrode winding body 62a is immersed in the electrolytic solution 62b, so the battery reaction proceeds over the entire negative electrode. As large current discharge progresses, as Li ions are inserted into the negative electrode active material, the electrolytic solution is pushed out from the negative electrode active material. When the flat plate without slits and the battery cell 62 are alternately stacked on top of each other, the pushed-out electrolytic solution moves towards the end of the battery case. That is, the electrolytic solution moves to both ends in the winding axis direction A of the electrode winding body 62a, and the electrolytic solution decreases in the central side of the electrode (the central side in the winding axis direction), and the reaction area of the negative electrode decreases (B). As the large current charge / discharge further progresses, the electrolytic solution becomes depleted at the central part of the electrode, and the reaction area significantly decreases (C).

[0044] In contrast, in this embodiment, when plates 63 with slits 71 are placed on both sides of each battery cell 62, when the restraint load F becomes a large load F1 due to large current charging / discharging, each battery cell 62 is strongly pressed at the portion where the base surface (contact portion) 63a of the plate 63 shown in Fig. 4 abuts. On the other hand, no pressing force is applied to the portion of each battery cell 62 that corresponds to the slit (recess) 91 of the plate 63.

[0045] Because the slits 91 in the plate 63 extend in a direction perpendicular to the winding axis direction A, the electrolyte present in the portion of the battery cell 62 corresponding to the slits 91 in the plate 63 is prevented from moving toward both ends of the battery cell 63 in the winding axis direction A in the portion where a pressing force is locally applied from the base surface 63a of the battery cell 63. In other words, the electrolyte in the portion corresponding to the slits 91 tends to remain in that portion, and even if high-current charging and discharging continues, it is possible to avoid the electrolyte in the center of the electrode drying up and the reaction area decreasing significantly (the progression of high-rate degradation is suppressed).

[0046] The resistance increase rate of the battery cell 62 was measured when a large current charge / discharge cycle was continued and then stopped for a case using a flat plate without a slit and a case using a plate 63 with a slit 91. The results are shown in Figure 9. In the case of the flat plate, the resistance increase rate increased significantly as the large current charge / discharge time increased. In contrast, in the case of the plate 63 with a slit, the resistance increase rate did not increase significantly even when the large current charge / discharge time was extended.

[0047] Furthermore, during low-current charging and discharging where the charging and discharging current value I is less than the predetermined current value Io, the restraining load F becomes the standard load F2, so the battery reaction proceeds without hindrance even at the portion of the battery cell 62 where the base surface 63a of the plate 63 abuts.

[0048] Furthermore, the plate 63 has slits 91, which is advantageous for reducing the weight of the battery module 60, and since there is no need to increase the plate thickness, it does not hinder the compactness of the battery module 60 in the stacking direction D.

[0049] (Control flow when IG-OFF) The control flow during IG-OFF is shown in Figure 10. Control starts by turning off the ignition of the hybrid vehicle 100 (IG-OFF). After the start, in step B1, it is determined whether the deterioration evaluation value N immediately before IG-OFF is less than 1. If the deterioration evaluation value N is less than 1, the process proceeds to step B2, where the constraint load variable mechanism 80 is controlled so that the constraint load F applied to the battery cell 62 becomes a small load F3. As the constraint load F becomes smaller, the pressing force applied from the base surface (contact portion) 63a of the plate 63 to the battery cell 62 weakens.

[0050] In the next step B3, a map (corresponding to characteristic line L1 in FIG. 6) showing the relationship between the degradation evaluation value N and the charge / discharge pause time is read out. In the next step B4, the degradation evaluation value N is calculated from the charge / discharge pause time (the time elapsed since the IG-OFF). For example, if the degradation evaluation value N immediately before the IG-OFF is 0.8 and the pause time is about 2 hours, the degradation evaluation value N will be about 0.9.

[0051] In the following step B5, it is determined whether or not the ignition is turned on (IG-ON). If the ignition is not turned on, the process proceeds to step B6, and if the ignition is turned on, the process proceeds to step B7. In step B6, it is determined whether or not the deterioration evaluation value N has reached 1 (N<1). If the evaluation value N has not reached 1, the process returns to step B4, and the ignition is not turned on, and it is continuously monitored whether or not the deterioration evaluation value N has reached 1 (steps B4-B6). If it is determined in step B6 that the deterioration evaluation value N has reached 1, the process proceeds to step B7.

[0052] When the power is turned on or the deterioration evaluation value N reaches 1, in step B7, the variable restraint load mechanism 80 is controlled so that the restraint load F applied to the battery cell 62 becomes the standard load F2. Then, in the following step B8, the evaluation value N is recorded in the control device 70 and the control ends.

[0053] As described above, when the degradation evaluation value N has not reached 1 (when the battery has not recovered from high-rate degradation) during IG-OFF (when charging / discharging is suspended), the restraint load F applied to the battery cell 62 becomes the small load F3, and the pressing force applied to the battery cell from the base surface (contact portion) 63a of the plate 63 is weakened. This facilitates the movement of the electrolyte within the battery cell 62, eliminating uneven electrolyte distribution, i.e., accelerating recovery from high-rate degradation. L2 in FIG. 6 is the characteristic line for the degradation evaluation value N when the restraint load F is the standard load F2. Because the restraint load F becomes the small load F3, accelerating recovery from high-rate degradation, the degradation evaluation value is calculated using the characteristic line L1, which shows a high rate of increase in the degradation evaluation value N as the rest time increases. In other words, the difference between the characteristic lines L1 and L2 represents the effect of setting the restraint load F to the small load F3.

[0054] 9, when the rate of increase in resistance of the battery cell 62 when charging and discharging are suspended is examined, when the restraint load F remains at the standard load F2 (the dashed line in the figure), the rate of increase in resistance accompanying suspension of charging and discharging decreases gradually. In contrast, when the restraint load F3 is changed to the small load F3, the rate of increase in resistance accompanying suspension of charging and discharging decreases more rapidly. This shows that the pressing force applied to the battery cell from the base surface (contact portion) 63a of the plate 63 is weakened, facilitating the movement of the electrolyte within the battery cell 62 and hastening recovery from high-rate degradation.

[0055] <Another embodiment> 11 shows another example of the plate 63. This plate 63 has a plurality of ribs 92 on both sides thereof that extend in a direction perpendicular to the winding axis direction A of the electrode winding body 62a and are arranged at intervals in the winding axis direction. The ribs 92 are formed at corresponding positions on both sides of the plate 63. Each of the plurality of ribs 92 is an electrode. pondThe plate 63 forms a contact portion that contacts the cell 62, and the portion between the ribs 92 on the plate 63 forms a recess 93 that is recessed relatively from the rib (contact portion) 92.

[0056] In this example, when a large constraint load F1 is applied to the battery cell 62 by the constraint load variable mechanism 80 in association with high-current charging and discharging, the battery cell 62 is strongly pressed at the portion where the rib 92 of the plate 63 abuts. On the other hand, no pressing force is applied to the portion of the battery cell 62 that corresponds to the recess 93 of the plate 63. Because the rib 92 of the plate 63 extends in a direction perpendicular to the winding axis direction A, the electrolyte present in the portion of the battery cell 62 that corresponds to the recess 93 of the plate 63 is prevented from moving toward both ends of the battery cell 62 in the winding axis direction A at the portion of the battery cell 62 where the rib 92 applies localized pressing force. Therefore, even if high-current charging and discharging continues, it is possible to avoid a significant decrease in the reaction area due to the electrolyte in the center of the electrode drying up (the progression of high-rate degradation is suppressed). In the case of the ribbed plate 63 of this example, the ribs 92 make it easy to ensure rigidity, and since there are no slits like the plate 63 of the previous embodiment, it has a strong function of separating adjacent battery cells 62, which is advantageous in preventing the battery cells 62 from spreading fire.

[0057] Although the battery cells 62 in the above embodiment are wound, the battery cells 62 may also be stacked. Fig. 12 shows an example of an electrode stack 85 housed in a battery case 65 together with an electrolyte. This electrode stack 85 is formed by alternately stacking multiple positive electrode sheets 66 and multiple negative electrode sheets 67 with separators 68 interposed between them. 66a denotes a positive electrode tab lead connected to each positive electrode sheet 66, and 67a denotes a negative electrode tab lead connected to each negative electrode sheet 67.

[0058] FIG. 13 shows a plate 63 suitable for the stacked battery cell. This plate 63 has a plurality of through-holes 94 arranged at intervals in both the vertical and horizontal directions. In this example, each through-hole 94 is rectangular, so the plate 63 has a lattice shape. The base surface 63a of the plate 63 where the through-holes 94 are open is the electrode. pond The through holes 94 form contact portions that come into contact with the cells 62, and each of the through holes 94 forms a recess.

[0059] 13, when a large constraint load F1 is applied to the battery cell 62 by the constraint load variable mechanism 80 in association with large current charging / discharging, the battery cell 62 is strongly pressed at the portion where the base surface (contact portion) 63a of the plate 63 abuts. On the other hand, no pressing force is applied to the portion of the battery cell 62 that corresponds to the through-hole (recess) 94 of the plate 63.

[0060] Because the through-hole (recess) 94 is surrounded by the base surface (contact portion) 63a, the electrolyte present in the portion of the battery cell 62 corresponding to the through-hole 94 of the plate 63 is prevented from moving toward the periphery of the battery cell 62 in the portion where a strong pressing force is applied from the base surface 63a of the battery cell 63. Therefore, even if high-current charging and discharging continues, it is possible to avoid the electrolyte in the center of the electrode drying up and a significant decrease in the reaction area (the progression of high-rate degradation is suppressed).

[0061] 13 is advantageous in reducing the weight and size of the battery module 60, as is the plate 63 having the slits 91 shown in FIG.

[0062] FIG. 14 shows another plate 63 suitable for the stacked battery cell. Unlike the plate 63 in FIG. 13, this plate 63 has a plurality of blind holes 95 spaced apart vertically and horizontally on both sides of the plate 63 rather than through holes 74. The blind holes 95 on both sides of the plate 63 are provided in a corresponding manner. The base surface 63a of the plate 63 where the blind holes 95 are open is the electrode. pond The holes 95 form contact portions that come into contact with the cells 62, and each of the plurality of bottomed holes 95 forms a recess.

[0063] 14 , when a large constraint load F1 is applied to the battery cell 62 by the constraint load variable mechanism 80 in association with large current charging / discharging, the battery cell 62 is strongly pressed at the portion where the base surface (contact portion) 63a of the plate 63 abuts. On the other hand, no pressing force is applied to the portion of the battery cell 62 that corresponds to the bottomed hole (recess) 95 of the plate 63.

[0064] Because the bottomed hole (recess) 95 is surrounded by the base surface (contact portion) 63a, the electrolyte present in the portion of the battery cell 62 corresponding to the bottomed hole 95 of the plate 63 is prevented from moving toward the periphery of the battery cell 62 in the portion where a strong pressing force is applied from the base surface 63a of the battery cell 63. Therefore, even if high-current charging and discharging continues, it is possible to avoid the electrolyte in the center of the electrode drying up and a significant decrease in the reaction area (the progression of high-rate degradation is suppressed).

[0065] In the plate 63 shown in FIG. 14, the recesses are formed by bottomed holes 95 rather than through holes, which effectively separates adjacent battery cells 62, is advantageous in preventing the battery cells 62 from catching fire, and also makes it easier to ensure plate rigidity.

[0066] The battery unit control device of the present invention is applicable not only to the hybrid vehicle 100 as described above, but also to electric vehicles (EVs). [Explanation of symbols]

[0067] 60 Battery Module 62 battery cells 62a Electrolyte 63 Plate 63a Base surface (contact part) 65 Battery Case 66 Positive electrode sheet 67 Negative electrode sheet 68 Separator 70 Control device 80 Variable restraint load mechanism 85 Electrode laminate 91 Slit (recess) 92 Rib (contact part) 93 Recess 94 Through hole (recess) 95 Bottomed hole (recess) 100 vehicles 110 Battery Unit

Claims

1. A control device for a vehicle battery unit configured by connecting a plurality of chargeable and dischargeable battery cells in series, the battery unit includes a battery module in which the plurality of battery cells and a plurality of plates are alternately stacked and constrained in the stacking direction, and a constraint load variable mechanism that changes the constraint load applied to each battery cell via the plates on both sides of the battery cell, the plate, which is disposed on at least one side of each battery cell, has, on a surface facing the battery cell, a contact portion that contacts the battery cell by the restraint load and applies a pressing force to the battery cell to suppress movement of the electrolyte in the battery cell toward the end of the battery cell, and a recess that is recessed relatively compared to the contact portion; a restraint load control unit that operates the restraint load variable mechanism so that the restraint load applied to the battery cells is larger during large current charging / discharging of the battery module at a predetermined current value or more than that during small current charging / discharging of the battery module at a current value less than the predetermined current value.

2. In claim 1, the restraint load control unit operates the restraint load variable mechanism during a charge / discharge pause in which the battery module is not charging or discharging so that the restraint load applied to the battery cell is smaller than during the low-current charge / discharge.

3. In claim 1 or claim 2, The battery cell is configured such that a positive electrode sheet and a negative electrode sheet are wound and flattened in a state insulated from each other via a sheet-like separator, and the electrode wound body is housed in a battery case together with an electrolyte, the plate disposed on at least one side of each battery cell has a plurality of slits that extend in a direction perpendicular to the winding axis direction of the electrode winding body and are spaced apart in the winding axis direction, the base surface of the plate where the slits are open forms the abutment portion that abuts against the battery cell, and each of the plurality of slits forms the recess.

4. In claim 1 or claim 2, The battery cell is configured such that a positive electrode sheet and a negative electrode sheet are wound and flattened in a state insulated from each other via a sheet-like separator, and the electrode wound body is housed in a battery case together with an electrolyte, the plate arranged on at least one side of each battery cell has a plurality of ribs that extend in a direction perpendicular to the winding axis direction of the electrode winding body and are arranged at intervals in the winding axis direction, each of the plurality of ribs forming the abutment portion that abuts against the battery cell, and the space between the plurality of ribs forming the recess.

5. In claim 1 or claim 2, The battery cell is configured such that an electrode stack, in which a plurality of positive electrode sheets and a plurality of negative electrode sheets are alternately stacked with separators interposed therebetween, is housed in a battery case together with an electrolyte; a plate disposed on at least one side of each battery cell, the plate having a plurality of through holes, the base surface of the plate into which the through holes are opened forming the abutment portion that abuts against the battery cell, and each of the plurality of through holes forming the recess.

6. In claim 1 or claim 2, The battery cell is configured such that an electrode stack, in which a plurality of positive electrode sheets and a plurality of negative electrode sheets are alternately stacked with separators interposed therebetween, is housed in a battery case together with an electrolyte; a base surface of the plate, which is disposed on at least one side of each battery cell, that has a plurality of blind holes, the base surface of the plate having the blind holes open therethrough, which constitutes the abutment portion that abuts against the battery cell, and each of the plurality of blind holes constitutes the recess.

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