JP4892813B2 - Single cell inspection method and assembled battery assembly method - Google Patents

Description

  The present invention relates to a method for inspecting a unit cell used for an assembled battery and an assembled method for the assembled battery.

For example, high-power lithium-ion batteries are used in electric vehicles. Usually, a plurality of (for example, 20 to 30) single cells (battery cells) are connected in series to form an assembled battery (battery module). The unit cell has a structure in which an electrode body in which a separator sheet is inserted and laminated between a positive electrode material sheet and a negative electrode material sheet is sealed together with an electrolyte in a battery container. In this type of unit cell, the battery container repeatedly expands and contracts because gas is generated or the electrode sheet expands due to a chemical reaction during charging and discharging. Therefore, in order to prevent short circuit failure even if the electrode sheet expands due to charge / discharge, the electrode plate group is added before inserting the electrode plate group of the unit cell into the battery container (battery). Patent Document 1 proposes a method for inspecting a short circuit defect while pressing.
JP 2001-236985 A

  In the case of an assembled battery to be mounted on an electric vehicle or the like, a large number of single cells are arranged in a stacked manner and assembled so that a compressed state in which a certain load is applied to the arranged single cell group is maintained. When the compressed state is maintained, it is possible to prevent the unit cell from rattling during use, and to reduce the contact resistance inside the unit cell. When assembled in such a manner that the compressed state is maintained, the mechanical characteristics of the assembled battery are stabilized and the battery performance is improved. A bus bar is welded to the terminals of the cell groups constituting the assembled battery, and the cell groups are connected in series or in parallel.

  When assembling the assembled battery as described above, even if the assembled battery is configured by arranging good cells that have passed the individual inspection, a defective cell may be incorporated in the assembled battery. This is because there is a unit cell that becomes defective when pressed together with the container even if it is a non-defective product. If a defective cell is incorporated in the assembled battery, the assembled battery becomes defective. Although the assembled battery can be disassembled and the defective cell can be replaced with a non-defective product, it is necessary to remove the welded bus bar, and there is a problem that it takes a lot of man-hours.

  The present invention has been made in view of the above circumstances, and provides a method for inspecting a unit cell that enables a good assembled battery to be assembled with a high yield. A method for efficiently assembling an assembled battery is also provided.

The present invention provides a method for inspecting a single cell constituting an assembled battery. In this inspection method, a plurality of unit cells constituting the assembled battery are arranged in a stacked manner, and the good / bad of each unit cell is inspected before assembling the assembled battery while pressing the arranged unit cell group in the stacking direction. .

In this inspection method, since the unit cells are pressed in the stacking direction, each unit cell is inspected for good / bad. Therefore, in the single-unit inspection, even if it is a non-defective product, the unit cell that becomes defective when pressed into the assembled battery Can be found, and it is possible to prevent a unit cell that becomes defective when incorporated into an assembled battery from being incorporated into the assembled battery. Before welding the connection member (bus bar) to the cell terminals, it is possible to detect defective cells when they are pressed and assembled into the assembled battery even if they are non-defective. It can be easily replaced with a good cell even if it is pressurized.
A typical example of the unit cell is a lithium ion battery. When the unit cell has an electrode having a laminated structure, it is preferable that the stacking direction of the electrode and the arrangement (pressing) direction of the unit cell are matched. In order to arrange a plurality of unit cells in a stack, it is convenient to use flat unit cells. The inspection of the unit cell includes the inspection of the battery performance and the shape dimension, and determines whether the unit cell is good or defective. Includes measurement of battery voltage and measurement of internal resistance.

It is preferable to inspect each unit cell in a pressed state until the unit cell group reaches a specified size to be finished as an assembled battery.

When pressing the unit cell group, a case of pressing with a specified load and a case of pressing until a specified size is assumed. When the assembled battery is configured, if it is finished to a specified dimension, installation work of the assembled battery and the like can be easily performed.
Therefore, if the unit cell group is pressed to the specified size, that is, the assembled battery is inspected with the specified size, each unit cell can be inspected with the assembled battery assembled. This makes inspection more effective. Further, since the assembled battery may be completed while maintaining the compressed state at the time of inspection, a substantial part of the inspection process and the assembly process can be used together, and the production efficiency of the assembled battery is improved.
In addition, in order to perform inspection in anticipation of secular change, it is possible to perform inspection by compressing the battery pack to a size smaller than a specified dimension for finishing the assembled battery. Or you may make it test | inspect, pressing with a predetermined load depending on the assembly method of an assembled battery.
The method of inspecting the unit cell group in a pressed state until reaching the specified size is effective when finishing the assembled battery to the specified size, but the compressed state for inspecting the unit cell is not limited thereto.

The present invention also provides an assembled battery assembly method. In this assembling method, a step of arranging a plurality of unit cells constituting the assembled battery in a stacked form, a step of pressing in the stacking direction until the arranged unit cell group reaches a specified dimension to be finished as an assembled battery, and assembling the assembled battery Before, the step of inspecting each unit cell of the unit cell group pressed to the specified size, and the unit cell group confirmed that all the unit cells are normal are held at the specified size by the holding member And a step of connecting the terminals of the unit cell group held in the above-mentioned specified dimensions with a connecting member (for example, a bus bar).

In this assembling method, in order to assemble a plurality of single cells constituting the assembled battery into the assembled battery, the single cell groups are arranged in a stacked manner, and pressed in the stacking direction until the arranged single cell groups reach a specified size. Normally, the unit cell group that is pressed until it reaches the specified size is held to the specified size by the holding member, and the terminals of the unit cell group that are held to the specified size are connected to each other by the connecting member.
In this assembling method, each unit cell is individually inspected while being pressed in the stacking direction until the arranged unit cell group reaches a specified size. For this reason, even if it is a non-defective product, it can be detected if there are mixed cells that become defective when pressed and assembled into the assembled battery. There is no assembly. It is possible to assemble the assembled battery after confirming that all the unit cells have no problem even if they are incorporated into the assembled battery.
In addition, the arrangement process and the compression process for the inspection simultaneously serve as the arrangement process and the compression process for assembling the assembled battery, and the unit cell group that has been pressed and passed the inspection as it is to the specified size remains as it is. The assembled battery is completed by holding the battery cell at a specified size by the holding member and connecting the terminals of the unit cell group by the connecting member.
Since the holding member can be easily held or released, it can be held before inspection. Although both are equal, it is more reasonable to hold after inspection because there is no need to re-hold when defective.

According to the present invention, since each unit cell is inspected while being pressed in the stacking direction before assembling the assembled battery, even if it is a non-defective product, it is defective when it is pressurized and assembled into the assembled battery. If a single cell is mixed, it can be discovered, and an assembled battery is not assembled in a state where a defective single cell is mixed. The assembled battery can be manufactured with high yield.
In addition, a substantial part of the inspection process and the assembly process can be used together, and the assembled battery can be manufactured efficiently.

First, the main features of the embodiments described below are listed.
(Embodiment 1) A plurality of unit cells are arranged in a stacked manner, and the electrical characteristics and mechanical properties (dimensions, etc.) of each unit cell are measured while pressed in the stacking direction.
(Mode 2) The characteristics of each unit cell are measured in a state where a predetermined number of unit cells are pressed and compressed to the size of the assembled cell.
(Mode 3) An inspection process for each unit cell is incorporated in the assembly process of the assembled battery, and each unit cell is inspected before connecting the terminals of the unit cells with the connecting member.

FIG. 1 is a perspective view for explaining an inspection apparatus according to an embodiment of the present invention. First, the cell to be inspected will be described. In the figure, two types of cell 1 and cell 2 having different shapes are illustrated. Both are lithium ion secondary batteries. This inspection apparatus can inspect the unit cell 1 or the unit cell 2.
The unit cell 1 has a configuration in which an electrode body wound in a state in which a foil-like positive electrode material and a foil-like negative electrode material are insulated by a film-like separator is sealed together with an electrolytic solution in a metal battery container. . As shown in the figure, in order to make it easy to secure a heat radiation area and a cooling air passage, the unit cell 1 has an uneven front and rear end surfaces, and a positive electrode terminal 1a and a negative electrode terminal 1b project from the upper end. .
The unit cell 2 has a configuration in which an electrode body wound in a state where a foil-like positive electrode material and a foil-like negative electrode material are insulated by a film-like separator is sealed together with an electrolytic solution in a battery container made of an exterior resin film. ing. The unit cell 2 is protected by a frame-like frame. From the unit cell 2, a positive electrode lead 2 a that also serves as a heat sink and a negative electrode lead 2 b that also serves as a heat sink project from the left and right.
A predetermined number of single cells 1, 1, 2, and 2 are arranged in a stacked manner, and constraining plates 3, 3, 4, and 4 are provided for sandwiching them from the front and rear. Screw holes 3a and 4a are formed at both upper and lower ends of the restraining plates 3 and 4. As will be described in detail later, by fixing the holding member using the screw holes 3a and 4a, the cell groups 1 to 1 are formed. 1, 2 and 2 can be constrained to specified dimensions. Thereafter, the unit cells 1, 1, and 2 are electrically connected by the bus bar to form the assembled battery. The inspection object may be another type of battery, and the following description will be represented by the single battery 1.

  Next, the inspection apparatus will be described. Reference numeral 11 in FIG. 1 denotes a case that also serves as an assembly jig and an inspection jig for storing the cell groups 1 to 1 together with the restraint plate 3 in a stacked shape. The case 11 is slidably provided with a pressing plate 12 that is brought into contact with the restraining plate 3. The screw rod 13 that extends rearward from the pressing plate 12 and engages with the screw hole of the case rear wall 11 a rotates to rotate. The plate 12 can be moved back and forth. The rear end of the threaded rod 13 is connected to a geared motor 15 as a driving device through a pair of joints 14. The amount of movement of the pressing plate 12 is detected via a linear slider sensor 16 that is a length measuring device, and the pressing force when the pressing plate 12 presses the restraint plate 3 is a load cell 17 such as a piezoelectric element provided on the front surface of the pressing plate. Is detected through. The pressing device for arranging the cell groups 1 to 1 and pressing them in the stacking direction is configured as described above.

  A probe support 18 provided with probes 18a and 18b to be brought into contact with the positive electrode terminal 1a and the negative electrode terminal 1b of the unit cell 1 is provided above the case 11 so as to be movable through a probe drive mechanism (not shown). Yes. The probes 18a and 18b are connected to the control device 20, and the battery voltage and internal resistance of the unit cell 1 are measured by a voltmeter and a milliohm resistance meter that the control device 20 has. The linear slider sensor 16 and the load cell 17 are also connected to the control device 20, and the moving amount of the pressing plate 12 and the pressing force applied to the unit cell 1 are measured by a length meter and a load meter that the control device 20 has. The control device 20 can process measurement data by a built-in microcomputer. Further, the control device 20 is also connected to the CCD camera 19, and from the image data of the single cell groups 1-1, the thickness dimension of the single cell 1 (pitch between adjacent single cells), the positive terminal 1a and the negative terminal 1b. Measure the position and pitch between terminals. The control device 20 is connected to the geared motor 15 and controls it on and off. In addition, the control apparatus 20 can test | inspect each cell 1-1 sequentially according to the program memorize | stored in the memory | storage device of the microcomputer.

Now, an assembled battery assembling method including a cell inspection method performed using the inspection apparatus will be described in the order of steps with reference to the flowchart shown in FIG.
[Arrangement Step] First, a predetermined number of single cells 1 to 1 are arranged between the two constraining plates 3 and 3 and are arranged in a stacked manner in the case 11 (step S2).
[Preparation] Next, the case 11 (inspection jig) is set in an inspection apparatus. That is, as shown in FIG. 1, the drive device is connected via the joint 14, and the linear slider sensor 16 and the load cell 17 are connected to the control device 20 via a connector (not shown). Further, the probes 18a and 18b of the probe support 18 arranged at a predetermined position and the CCD camera 19 are connected to the control device 20 (step S4). When the control device 20 is activated, the control device 20 performs self-diagnosis as to whether or not the function of each connected unit is normal.

[Pressing Step] When the operator presses the pressing device driving button of the control device 20, the geared motor 15 rotates in the forward direction, and the pressing plate 12 of the pressing device moves forward to compress the cell groups 1-1 (step S6). ). Finally, the cell groups 1 to 1 are compressed to the specified dimensions as an assembled battery. The procedure will be described in detail below. FIG. 3A is a graph showing the transition of the load applied to the cell groups 1 to 1, with the horizontal axis representing time and the vertical axis representing the load. A graph showing the stroke of the pressing plate 12 on the same time axis, that is, the compression amount of the cell groups 1 to 1 is shown in FIG. When the compression starts and the geared motor 15 continues to rotate, as shown in the graph, the stroke of the push plate 12 extends and the compression load increases. Meanwhile, the microcomputer continues to compare the measured load with the set value by the execution program, and determines whether or not the first predetermined load P1 has been reached (step S8). If it is determined that the first predetermined load P1 has been reached at time t1, the process proceeds to the next step, where the rotation of the geared motor 15 is stopped and the compression is interrupted (step S10). At this time, the push plate 12 is stationary at the position of the stroke C1. In some cases, the geared motor 15 may be rotated in the reverse direction so that the push plate 12 is returned to a slightly returned position. If this state is maintained for a while, the inside of the unit cell 1 becomes familiar and the compressive load gradually decreases. In the meantime, the microcomputer continues to compare the measured load with the set value and determines whether or not the second predetermined load P2 has been reached (step S12). When it is determined that the second predetermined load P2 has been reached at time t2, the process proceeds to the next step, where the geared motor 15 is turned on and compression is resumed (step S14).

  Subsequently, it is determined whether or not the cell groups 1 to 1 have a predetermined size (step S16). That is, the microcomputer continuously obtains the compression amount of the cell groups 1 to 1 from the stroke of the push plate 12 and compares it with the set value. If the stroke does not reach C3, the process goes to step S8. The compression interruption and restart described above are repeated. If it is determined that the predetermined size has been reached, the process proceeds to the next step. This state is indicated by a stroke C3 and a load P3 at time t5. That is, the compression amount corresponding to the stroke C3 is the planned compression amount of the assembled battery. As a result, the cell groups 1 to 1 have specified dimensions (fixed dimensions) as assembled batteries.

[Inspection Step] Subsequently, each cell is inspected for defects. First, it is determined whether or not the load P3 is within a predetermined allowable range (step S18). This load P3 may be replaced with the latest load obtained. If it is outside the allowable range, it is determined that defective cells are mixed, the inspection is stopped, and the process proceeds to step S32 of the defect processing described later. Possible causes of defects include abnormalities such as container deformation due to gas generation inside the battery. If the load P3 is within the allowable range, it is determined as a next inspection item whether the cell pitch and the terminal pitch between the adjacent single cells are within the predetermined allowable range (step S20). For this, the above-described measurement by image recognition is used. If it is outside the allowable range, it is determined that defective cells are mixed, and the process proceeds to step S32 of the defect processing described later. As the cause of the failure, an abnormality in the appearance such as battery thickness can be cited. An abnormality in the external dimensions is effective as a preventive measure because it interferes with the attachment of the restraint band and the pressure contact of the bus bar, which will be described later, and disturbs the process.

  If the cell pitch and terminal pitch are within the allowable range, the battery voltage and internal resistance are examined as the next inspection items. This is measured by moving the probe support 18 and sequentially pressing the probes 18a and 18b against the terminals of each unit cell 1. The probe movement can be automatically processed by using the measurement results of the cell pitch and terminal pitch in the previous process. First, it is checked whether or not the voltage value and the resistance value are within a preset allowable range for the first cell 1 (step S22). If an abnormality is detected, the inspection is stopped and the process proceeds to step S32 of a defect process described later. If it is normal, the voltage value and resistance value of the second and subsequent single cells 1 are checked in the same manner. If the inspection is completed for all the unit cells 1, the inspection process is terminated (step S24).

[Defect Processing] If it is determined to be defective in each of the above determination steps, the unit cell group is transferred to another process, or the defective unit cell is replaced through an operation for specifying the defective unit cell (step S32). When the replacement of the unit cell is completed, it is possible to return to the first step S2. In this failure processing, only defective cells can be replaced easily and quickly, which saves resources and is advantageous in terms of cost compared to the conventional case where the entire cell group has to be discarded. In addition, since it is difficult for the finished assembled battery to carry over defects, the yield is improved as a result.

[Holding Step] The cell groups 1 to 1 that have passed the inspection are restrained by a restraining tool and held in a compressed state at the time of inspection (step S26). Specifically, as shown in FIG. 4, four bands 5 as restraint fittings are passed between the restraint plates 3 and 3 at both ends, and screwed and fixed using the screw holes 3a. This may be considered as temporary fixing and may be reinforced in a separate process or additional welding may be added. Instead of screwing, welding may be performed from the beginning. It is also possible to replace with appropriate restraint means. In some cases, the compression amount of the cell groups 1 to 1 may be changed between the inspection time and the band restraint time.
[Removal] Next, the gear plate motor 15 is reversely rotated to retract the push plate 12, and the assembled cell groups 1 to 1 are removed from the case (step S28).
[Connection Step] As shown in FIG. 4, the taken out cell groups 1 to 1 are connected in series by welding the bus bar 6, which is a connection member, to the positive terminal 1 a and the negative terminal 1 b. (Step S30). As can be seen from the figure, the cell groups 1 to 1 are arranged in advance with their directions alternately reversed so that the positive electrode terminal 1a and the negative electrode terminal 1b are adjacent to each other between adjacent cell units. The bus bar 6 may be welded or pressed. In general, the bus bars are joined so as not to be disassembled, but in some cases, the bus bars can be replaced with screws or the like.
The assembled battery 10 is completed as described above. The cell groups 1 to 1 constituting the assembled battery 10 are guaranteed to be non-defective in the state of constituting the assembled battery 10.

As mentioned above, although embodiment of this invention was described in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

It is a perspective view explaining the inspection apparatus which concerns on an Example. It is a flowchart figure explaining the inspection method of the cell which concerns on an Example, and the assembly method of an assembled battery. (A) is a diagram which shows transition of the load added to the cell group which concerns on an Example, (B) is a diagram which shows the stroke of a press plate, ie, the compression amount of a cell group. It is a perspective view explaining the assembled battery which concerns on an Example.

Explanation of symbols

1, 2, single cell 1 a, positive electrode terminal 1 b, negative electrode terminal 2 a, positive electrode lead 2 b, negative electrode lead 3, 4, restraining plate 3 a, 4 a, screw hole 5, band 6, bus bar 10 ·· Battery 11 ·· Case 12 · · Push plate 13 · · Screw rod 14 · · Joint 15 · · Geared motor 16 · · Linear slider sensor 17 · · Load cell 18 · · Probe supports 18a and 18b · · Probe 19 ..CCD camera 20

Claims (3)

A method of inspecting a single cell constituting an assembled battery before assembling the assembled battery, in which a plurality of single cells are arranged in a stacked manner, and each arranged single cell group is pressed in the stacking direction. A method for inspecting a single cell, characterized by inspecting good / bad.   2. The inspection method according to claim 1, wherein each unit cell is inspected in a pressed state until a specified size is obtained to finish the unit cell group as an assembled battery. A method of assembling the battery pack, a step of pressing a plurality of unit cells and a step of arranging in layers, the stacking direction to the cell group which is arranged is defined dimensions to finish the assembled battery constituting the battery pack, the set A step of inspecting each unit cell of the unit cell group pressed to the specified size before assembling the battery, and holding the unit cell group confirmed that all the unit cells are normal to the specified size by the holding member A battery assembly method comprising: a step of connecting the terminals of the single cell group held at the specified size with a connection member.

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