JP6667409B2 - Judging method and joining apparatus for judging replacement of ultrasonic welding tool - Google Patents

Description

  The present invention relates to a determination method and a welding device for determining replacement of an ultrasonic welding tool.

  An electrode tab derived from a cell constituting the secondary battery is joined to a current collector housed inside the cell. The joining at the location may be performed by ultrasonic joining, and the ultrasonic joining is generally performed using an ultrasonic joining tool such as a horn or an anvil. Horns and anvils used for ultrasonic welding require replacement because wear or abrasion of a material to be welded to a tool progresses over time with use.

  As a conventionally known method of determining the replacement of an ultrasonic welding tool, there is a technique of detecting a change over time of a step provided at a processing portion of a tool for processing a work as a wear amount (see Patent Document 1). ).

JP 2014-104493 A

  The present inventor has studied the use of the tool for a longer period of time, and found that the tool can be used even when the wear amount of the step at the machining location has advanced to a considerable extent as in Patent Document 1. I found that there is.

  Accordingly, the present invention provides a method and a method for determining the replacement of an ultrasonic welding tool that can efficiently use a tool required for ultrasonic welding until near the life instead of the wear amount of a step at a processing location. It is an object of the present invention to provide a joining device that performs the following.

  The present invention for achieving the above object is a case where a joining portion is formed on a material to be joined including a plurality of members using an ultrasonic joining tool, and the ultrasonic joining is performed in consideration of repeated use of the ultrasonic joining tool. This is a determination method for determining replacement of a tool. The above-mentioned determination method sets a threshold value in advance for a peeling force when the ultrasonic welding tool is peeled off from the workpiece after forming the welding location, and makes the ultrasonic welding tool abut on one workpiece to form the welding location. Form. Then, a peeling force at the time of peeling the ultrasonic welding tool from one workpiece is measured, and the peeling force is compared with a threshold to determine whether to replace the ultrasonic welding tool.

  The present invention that achieves the above object is a joining device having a joining unit, a measuring unit, and a control unit. The joining portion forms a joining portion on a material to be joined including a plurality of members using an ultrasonic joining tool, and the ultrasonic joining tool is replaced by repeated use of the ultrasonic joining tool. The measuring unit measures a peeling force when the ultrasonic welding tool is peeled off from the material to be welded after the formation of the joining portion. The control unit previously stores a threshold value for the peeling force, and compares the peeling force with the threshold value to determine whether to replace the ultrasonic welding tool.

  ADVANTAGE OF THE INVENTION According to the determination method and joining apparatus in this invention, the tool required for ultrasonic welding can be used efficiently until near life.

It is an outline perspective view showing the joining device concerning one embodiment of the present invention. FIG. 3 is a partial cross-sectional view illustrating a joining device and illustrating an internal structure of a portion that generates ultrasonic waves. It is a perspective view which shows the processing front-end | tip part of the tool (horn) used for ultrasonic joining. It is a side view which shows the processing front-end | tip part of the tool (horn) used for ultrasonic joining. It is a front view which shows the processing front-end | tip part of the tool (horn) used for ultrasonic joining. FIG. 1 is a representative cross-sectional view of a secondary battery that is an example of a target to which a bonding method according to an embodiment of the present invention is used. 6 is a flowchart illustrating a method for determining tool replacement according to an embodiment of the present invention. 6 is a graph showing a relationship between time and load when the anvil is peeled off from the joint component when the joint component adheres to the anvil and when the joint component does not adhere to the anvil as one embodiment of the present invention. 4 is a graph showing a relationship between a time and a load when the horn is peeled off from the joined component when the joined component is attached to the horn or not, as one embodiment of the present invention. It is a front view showing the joining device concerning a modification of the present invention. FIG. 9 is a graph showing a relationship between a time and a load when the work and the tool are separated from each other. 6 is a graph showing a case in which data for determining replacement of data is corrected.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. The sizes and ratios of the members in the drawings are exaggerated for convenience of explanation and may be different from the actual sizes and ratios.

(Application example of the joining method according to the present embodiment)
FIG. 6 is a typical cross-sectional view of a secondary battery to which ultrasonic bonding according to an embodiment of the present invention is applied. Briefly describing the secondary battery 200, as shown in FIG. I have. The positive electrode 210 includes a positive electrode current collector 211 provided with a positive electrode active material layer 212, and the negative electrode 220 includes a negative electrode current collector 221 provided with a negative electrode active material layer 222. The secondary battery 200 shown in FIG. 6 is configured as a so-called stacked secondary battery.

  The positive electrode current collector 211 is joined to the positive electrode tab 213 near the outer periphery of the outer package 250 as shown in FIG. The negative electrode current collector 221 is joined to the negative electrode tab 223 in the vicinity of the outer periphery of the outer package 250, similarly to the positive electrode. The ultrasonic bonding according to the present embodiment is used when bonding the above-described positive electrode tab 213 and the plurality of positive electrode current collectors 211 and when bonding the negative electrode tab 223 and the plurality of negative electrode current collectors 221. You. In the following, the case where the electrode tab and the current collector are joined without distinction between the positive electrode and the negative electrode will be described.

(Joining equipment)
FIG. 1 is a perspective view showing a joining device according to an embodiment of the present invention, and FIG. 2 is a side view of FIG. The bonding apparatus 100 according to the present embodiment includes a transport unit 10, a bonding unit 20, a measuring unit 30, and a control unit 40, as generally described with reference to FIGS.

  The transport unit 10 has a mounting table 11 and a motor 12. The mounting table 11 is a table on which a plurality of materials to be bonded (members to be bonded) to be works are mounted. In the present embodiment, the mounting surface is made of a flat metal. The mounting table 11 is configured such that the right end in FIG. 2 extends beyond the positions of a horn 22 and an anvil 23 described later. The mounting table 11 is configured to penetrate a portion above the head of the anvil 23 (see the broken line in FIG. 1) so that the workpiece and the anvil 23 can abut. However, the material and shape of the mounting table are not limited to the above, as long as the work does not move or slide unintentionally during joining and the work can contact the horn 22 and the anvil 23.

  The motor 12 is housed in the housing shown in FIG. 2, and causes the mounting table 11 on which the work is mounted to approach the anvil 23 forming the joint 20 or separates the joined work from the anvil 23. Be configured for. The mounting table 11 is moved up and down in FIG. 2 by the motor 12 in the present embodiment, and approaches or separates from an anvil 23 forming a joint 20 described later. The motor 12 is configured as a servomotor in the present embodiment. However, the present invention is not limited to this as long as the mounting table 11 can be moved toward and away from the anvil 23.

  As shown in FIG. 2, the joint 20 includes a vibration generator 21, a horn 22, an anvil 23, a motor 24, and a spring 25. The vibration generator 21 is configured by an ultrasonic vibrator and a booster. The ultrasonic vibrator is constituted by a transducer or the like, and generates vibration corresponding to the frequency of the ultrasonic wave by electric power supplied from the outside. The ultrasonic transducer has one end connected to a booster and the other end connected to a power cable or the like. The booster is made of metal and is connected to the horn 22 and the ultrasonic vibrator. The booster amplifies the vibration generated by the ultrasonic transducer.

  3 to 5 are a perspective view, a side view, and a front view showing the tip of a horn used for ultrasonic bonding. The horn 22 generates frictional heat by applying ultrasonic waves to the joining surfaces of the current collectors or the electrode tabs constituting the work and causing them to vibrate. The horn 22 is configured to be able to move toward and away from the workpiece in the vertical direction in FIG.

  As shown in FIGS. 3 to 5, countless substantially quadrangular pyramids or truncated quadrangular pyramid projections 22 a are provided on the distal end surface of the horn 22. The tip of the protruding shape 22a contacts the work. The projection shape 22a is also called knurling or knurling. The tip of the protruding shape 22a wears due to repeated use, and the height from the apex to the root of the substantially quadrangular pyramid shown in FIG. 4 gradually decreases, which necessitates tool replacement. The replacement of the horn 22 and / or the anvil 23 will be described later.

  The anvil 23 is a table on which a joint portion of the work is placed when the work is joined by the horn 22, receives ultrasonic vibration from the horn 22, and holds the work together with the horn 22. The anvil 23 is provided with an infinite number of protrusions at the joint with the workpiece, similarly to the horn 22 shown in FIGS. 3 to 5. The horn 22 and the anvil 23 correspond to an ultrasonic welding tool in the present embodiment.

  The motor 24 moves the vibration generator 21 and the horn 22 closer to or away from the workpiece in the vertical direction in FIG. The spring 25 is configured to apply a reaction force to the pressing force of the motor 24 with respect to the vibration generating unit 21, whereby the position of the vibration generating unit 21 is maintained. Note that the motor 24 and the spring 25 constitute a moving unit of the vibration generating unit 21.

  The measuring unit 30 collects information on a peeling force when the horn 22 or the anvil 23 is peeled from the workpiece by measurement. The measurement unit 30 has force sensors 31, 32 and a position sensor 33 as shown in FIG. The force sensor 31 is installed to monitor a change in the pressing force when the joined workpiece is separated from the horn 22. The force sensor 31 can be, for example, a piezoelectric load cell, but is not limited thereto. The force sensor 32 monitors a change in the pressing force required to move the mounting table 11 of the transport unit 10 when separating the joined workpiece from the anvil 23.

  The position sensor 33 measures the position of the vibration generator 21 that is displaced in accordance with the operation of the motor 24. The position sensor 33 can be constituted by, for example, a linear encoder, but is not limited to this.

  The control unit 40 is configured by storing a CPU, a RAM, a ROM, and the like in the housing shown in FIGS. With these configurations, the control unit 40 forms a joint portion on the work using the horn 22 and the anvil 23, and then instructs the horn 22 and the anvil 23 to be separated from the work and separated. Further, the control unit 40 stores the peeling force when the horn 22 or the anvil 23 needs to be replaced as a threshold, and compares the measured value stored by the measuring unit 30 with the threshold to determine the tool replacement. Then, an instruction to change the tool is issued as needed. Details will be described later.

(Joining method)
Next, a joining method according to the present embodiment will be described. FIG. 7 is a flowchart illustrating the joining method according to the present embodiment. In the present embodiment, a case where the current collector and the electrode tab are joined in the secondary battery 200 shown in FIG. 6 will be described as an example. However, this is only an example, and the joining method according to the present invention can be applied to joining of works other than the secondary battery as long as two or more members are joined using ultrasonic waves.

  The bonding method according to the present embodiment will be briefly described with reference to FIG. 7. When the current collector and the electrode tab are bonded to each other and the anvil 23 or the horn 22 is separated from the current collector or the electrode tab, the horn 22 or the horn 22 is removed. A threshold for determining replacement of the anvil 23 is set (ST1). Next, a current collector and an electrode tab serving as a work are installed on the mounting table 11 (ST2). Next, a junction is formed at a predetermined position between the current collector and the electrode tab (ST3).

  Next, the horn 22 or the anvil 23 is separated from the work (ST4). Then, the peeling force (peeling load) when the horn 22 and the anvil 23 separate from the work is measured by the force sensors 31 and 32 (ST5), and the measured peeling force is compared with the set threshold (ST6). If the peeling force exceeds the threshold value, an instruction is given to change the tool (ST8). The details will be described below.

(About tool wear)
First, a threshold value for determining tool replacement will be described. FIG. 8 is a graph showing the relationship between the time and the load when the anvil is peeled off from the joined component when the joined component is attached to the anvil and when the joined component is not attached to the anvil as one embodiment of the present invention. FIG. 9 is a graph showing a relationship between a time and a load when the horn is peeled off from the joined component when the joined component is attached to the horn or not, as one embodiment of the present invention.

  The inventor of the present invention has intensively studied a matter of using a tool for a longer period of time.

  When the anvil 23 and the horn 22 are relatively new, the anvil 23 and the horn 22 are in contact with each other so as to bite into the work, and form a joint portion on the work while being firmly fixed to the work during ultrasonic vibration.

  On the other hand, when the anvil 23 or the horn 22 wears, the slip occurs between the anvil 23 or the horn 22 and the workpiece during the joining, and the joining may be performed in that state. In this case, an adhered portion (sticked portion) may be formed between the work and the anvil 23 or the horn 22 from a state where the slip has occurred.

  Then, depending on the adhesive force between the work and the horn 22 or the anvil 23, when the horn 22 or the anvil 23 is separated from the work and separated, the joint portion with the work may be deformed to some extent from a state before the work. is there.

  As described above, when the shape of the work is deformed from before the joining due to the joining, the assembling with other parts may be affected in a later process, or the work of returning the work to the original shape may be required. . It is necessary to prevent such a situation, and for that purpose, it is necessary to change a tool in use at an appropriate timing.

  As shown in FIGS. 8 and 9, there is sticking (see the solid line a in FIGS. 8 and 9) as compared with the case where the work does not stick to the horn 22 or the anvil 23 (see the broken line b in FIGS. 8 and 9). In (2), the force for peeling off the horn 22 or the anvil 23 from the work is partially increased. The present inventor has discovered that even when wear of the horn, anvil, or the like progresses, the work may not be deformed as described above and the joining operation may be performed without any problem. As an index of tool change, it is better to monitor the peeling force (peeling force) when the horn or anvil is peeled off from the work as described above, rather than the wear amount of the tool such as the horn or anvil. Was found to be able to be determined more appropriately.

  In the joining method according to the present embodiment, the data shown in FIGS. 8 and 9 is measured each time a joint is formed on a work using the horn 22 or the anvil 23, and the maximum value is used as the measured value. Then, when the horn 22 or the anvil 23 is peeled off from the work, the time when the work is deformed is specified, and for example, the peeling force at a point immediately before the point is recorded in the control unit 40 as a threshold value.

  In other words, the peeling force immediately before the current collector or the electrode tab is deformed is stored in the control unit 40 as a threshold. The threshold value may be a value obtained by multiplying the calculated or measured value by a safety factor, for example, 95% of the measured value, in order to prevent defective products from appearing. In addition, the load when the current collector and the electrode tab, which are works, are turned up, is simulated during the production line to prevent the above-mentioned situation from occurring when a mass production line is operated. It is measured and calculated in advance in an experiment separately from the line (ST1). Here, “before” in the above means that the threshold value is set at least at the latest before the point at which the control unit 40 to be described later determines that the tool should be replaced.

  Next, the work is set on the mounting table 11, the transport unit 10 is driven, the work is moved toward the anvil 23, and the work is brought into contact. Next, the horn 22 is moved toward the workpiece by the motor 24 and brought into contact with the workpiece (ST2). Then, energy is supplied to the vibration generating unit 21 to generate ultrasonic vibration in the horn 22 to form a joint in the work (ST3).

  Next, the motor 24 is driven to separate the horn 22 from the work and separate it (ST4). If the adhesion between the workpiece and the anvil or between the workpiece and the horn is large at the time of joining, the joint may be deformed. In the present embodiment, in order to prevent such a situation, the load at the time of peeling is measured by the force sensor 31 (ST5), and is compared with the threshold value obtained above (ST6).

  If the peeling force is lower than the threshold (ST6: YES), it is determined whether all the tools have been peeled off from the workpiece (ST7). At this time, only the horn 22 has peeled off (ST7: NO), so the mounting table 11 is moved to peel off the anvil 23 from the work (ST4), and the peeling force is measured by the force sensor 32 (ST5). , And a threshold value (ST6).

  When the peeling load is less than the threshold value (ST6: YES), all the tools are peeled off from the work at this time (ST7: YES). In this case, the control unit 40 determines that the tool is not to be replaced this time, and returns to step ST2 to set a new work (ST2), form a joint (ST3), peel off the tool (ST4), and The peel force is measured (ST5).

  If the peeling force exceeds the threshold value (ST6: NO), the control unit 40 determines that the horn 22 or the anvil 23 has become unsuitable for joining over time, and instructs to replace it with a new tool (ST8). The tool change instruction is not particularly limited as long as the operator can recognize the tool change, and may include a monitor (display), a display by a lamp, or a notification by a sound.

(Effects)
Next, the operation and effect according to the present embodiment will be described. In the present embodiment, the horn 22 and the anvil 23 are peeled off from the work after the work is joined, and the peeling force is compared with a predetermined threshold value to determine whether or not the tool is replaced. As described in the prior art, the present inventors have discovered that ultrasonic bonding is possible even when wear of a horn, anvil, or the like has progressed to a considerable extent.

  Therefore, it is determined that the tool should be replaced by using the peeling force when the horn 22 or the anvil 23 is separated from the work, instead of the wear amount of the horn 22 or the anvil 23 as in the above-described conventional technology, so that the tool can be used for a long time. Can be used

  Further, in step ST1 of the flowchart of FIG. 7, the threshold value for judging tool exchange can be obtained in advance in a separate experiment, not in a production line for mass production or the like. Thus, the tool can be changed before a defective joining product occurs in a production line such as mass production.

  Note that the present invention is not limited to the above-described embodiment, and various changes can be made within the scope of the claims. FIG. 10 is a front view showing a joining device according to a modification of the present invention. FIG. 11 is a graph showing a relationship between a time and a load when the work and the tool are separated from each other. In the case where the approach and the separation movement of the work and the tool are performed through the supply of the fluid, the pressure fluctuation of the supplied fluid is taken into consideration. 7 is a graph in which data for determining tool replacement is modified. In FIG. 10, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

  In the above, an embodiment has been described in which the mounting table 11 and the horn 22 constituting the transport unit 10 are moved using a servomotor, but the present invention is not limited to this. In addition to the above, for example, the mounting table 11 and the horn 22 may be moved by using air cylinders 12a and 24a instead of the servo motor as shown in FIG. In this case, fluid is supplied from the air cylinders 12a and 24a, and the mounting table 11 and the horn 22 are moved.

  When the mounting table 11 and the horn 22 are moved using the air cylinders 12a and 24a, as shown in FIG. 11, the fluid supplied from the air cylinder tends to fluctuate in pressure. May be reflected. If the tool is replaced using the change in the pressure applied by using the air cylinder as it is, the accuracy of the determination may be affected.

  Therefore, when pressurization is performed using a configuration like an air cylinder, the pressure of the air cylinder 12a is detected by the pressure sensor 35 and the pressure of the air cylinder 24a is detected by the pressure sensor 34 as shown in FIG. The pressing force is measured using the force sensors 31, 32 as in the above embodiment. Then, as shown by the dashed line c in FIG. 11, the tool change is determined using the solid line e obtained by subtracting the pressure fluctuation of the two-dot chain line d indicating the pressure of the air cylinder from the change in the pressing force before correction. As a result, it is possible to exclude the pressure fluctuation of the air cylinder from being included in the fluctuation of the pressing force, and it is possible to more appropriately determine the exchange of the tool.

  Further, in the above, the embodiment in which the tool exchange between the horn 22 and the anvil 23 is determined using the peeling force when the tool is peeled from the workpiece has been described, but the present invention is not limited to this. In addition to the above, it may be configured to determine the replacement of only one of the horn 22 and the anvil 23 using the peeling force.

  Further, in the above description, it is described that data when the work is deformed in an experiment or the like is obtained, and the threshold value is set therefrom, but the present invention is not limited to this. In addition to the above, an approximate curve indicating a change in the peeling load may be obtained by using data acquired every time until the work is deformed, and a tool replacement time may be predicted using this.

  Although the embodiment in which the bonding method according to the embodiment is applied to a stacked secondary battery has been described above, the present invention is not limited to this. In addition to the above, the present invention may be applied to, for example, a wound secondary battery. Although the embodiment in which the bonding method according to the present embodiment is applied to the bonding between the current collector and the electrode tab in the secondary battery has been described above, the present invention is not limited to this. In addition to the above, in a secondary battery, for example, it can be used for joining an electrode tab and a bus bar derived from a plurality of unit cells. In addition, other than the secondary battery, it may be used when joining the electrode foil and the tab in the capacitor.

10 transport section,
11 mounting table,
12, 24 motors,
12a, 24a air cylinder,
100 joining equipment,
20 joints,
21 vibration generator,
22 horn (ultrasonic welding tool),
23 anvil (ultrasonic welding tool),
25 spring,
30 measuring unit,
31, 32 force sensor,
33 position sensor,
34, 35 pressure sensor,
40 control unit.

Claims (4)

A case in which a joining portion is formed in a material to be joined including a plurality of members using an ultrasonic joining tool, and a determination is made to determine whether to replace the ultrasonic joining tool in consideration of repeated use of the ultrasonic joining tool. The method
A threshold value is previously set for a peeling force when the ultrasonic welding tool is peeled off from the material to be welded after the formation of the joining portion,
The ultrasonic welding tool is brought into contact with one of the workpieces to form the joint,
Measure the peeling force when peeling the ultrasonic welding tool from the one workpiece,
A method for determining whether to replace the ultrasonic welding tool by comparing the peeling force with the threshold.   2. The method according to claim 1, wherein when the position of the ultrasonic welding tool and the material to be joined is adjusted by supplying a pressure of a fluid, the peeling force is corrected in consideration of a variation in a supply pressure of the fluid. Judgment method.   The method according to claim 1, wherein the ultrasonic welding tool is at least one of a horn and an anvil. Using an ultrasonic welding tool to form a joint in the material to be welded including a plurality of members, the ultrasonic welding tool is replaced by repeated use of the ultrasonic welding tool, the welding portion,
A measuring unit that measures a peeling force when peeling the ultrasonic tool from the material to be joined after the formation of the joining portion,
And a controller that stores a threshold value for the peeling force in advance, and compares the peeling force with the threshold value to determine whether to replace the ultrasonic welding tool.