JP2532799B2 - Welding work placement condition determination method for cylindrical batteries - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention determines whether a lead plate to be welded to the inner bottom of a case of a cylindrical battery immediately before spot welding is located at a proper position and is in good contact with the inner bottom of the case. On how to inspect.

[0002]

2. Description of the Related Art A lead plate led out to the lower end of a spirally wound power generating element is bent through an insulating plate so as to close a through hole formed in the central portion of the power generating element, and has a tubular shape. Of the spot welding electrode, which is housed in the battery case, is positioned on the inner bottom of the battery case as a welding work and is in contact with the welding work by being inserted into the through hole of the central portion of the power generation element, and In a cylindrical lithium battery formed by sandwiching and pressing the welding work and the battery case inner bottom by the other electrode that contacts the battery case, and spot welding the welding work and the battery case inner bottom. , The lead plate is made of a thin metal plate and is easily deformed. If it is not located at the proper position due to some reason, welding failure will occur, leading to lower yield and battery performance. Because, it is provided whether a confirmation means positioned to the welding position of the normal inner bottom of the battery case.

As the confirmation means, a method of visually inspecting whether or not the lead plate is located at the center of the spiral before housing the power generating element in the case, and further performing an internal fluoroscopic inspection by X-ray after the battery is assembled, Alternatively, there is a method in which a resistance film is provided on the surface of the lead plate in advance and the difference in contact resistance between the lead plates is read by monitoring the current value during welding to determine the presence or absence of the lead plate. The inspection method had the following problems.

[0004]

First, in the visual confirmation method, even if the lead plate is located at the regular position before the packaging, the lead plate may be displaced at the time of packaging, which is not reliable. In addition, in the X-ray inspection method, the position of the lead plate is not in a rotationally symmetrical position, so the inspection must be performed while rotating the battery case, which requires man-hours and equipment costs for monitoring and labor costs. , The cost will be higher.

Further, the resistance film monitoring system has a drawback that the resistance film causes severe electrode consumption during welding and lowers reliability such as welding strength.

In any case, except for the visual inspection method, if the lead plate is not in the proper position, it is treated as a defective product and cannot be reassembled again.

The present invention eliminates the drawbacks of any of the above inspection methods. The purpose of the present invention is to set the lead plate to the normal welding position immediately before welding after the power generating element is housed in the case. It is an object of the present invention to provide a welding work arrangement state determination method for a cylindrical battery, which can surely and easily determine whether or not it is located.

[0008]

In order to achieve the above object, the present invention provides a lead plate led out to the lower end of a spirally wound power generating element with a central portion of the power generating element through an insulating plate. Bend to close the through hole formed in
A spot welding electrode that is housed in a cylindrical battery case, positions the lead plate as the welding work on the inner bottom of the battery case, and is inserted into a through hole at the center of the power generating element to contact the welding work. A cylindrical battery formed by spot welding the welding work and the battery case inner bottom by sandwiching and pressing the welding work and the battery case inner bottom by the other electrode in contact with the battery case. A power supply connected between the spot welding electrode and the other electrode in contact with the battery case, and a current monitoring means for indicating the current value of the current supplied from the power supply are provided, and the welding current is supplied. Before the spot welding, a weak current equal to or lower than the welding current is flown from the power source, and the welding work is moved according to the current value read by the monitor means. It is to determine whether Tsu is disposed at a position of regular contact with preparative welding electrode.

[0009]

With the above construction, the current value changes according to the contact resistance between the lead plate, which is the welding work, and the spot welding electrode. Therefore, the correlation between the current value and the lead plate arrangement should be investigated in advance. Thus, it is possible to determine whether or not the lead plate is at the proper position by reading the current value through the monitor means. For example, when the lead plate is not in the proper position and the spot welding electrode is in direct contact with the inner bottom of the battery case, the contact resistance is small, and the monitored current value is larger than that in the normal state.

Further, when an oxide film or the like is formed on the surface of the lead plate, the welding work is performed after the oxide film is removed by the weak current during the inspection, so that good spot weldability is obtained. The spatter generation rate during welding is extremely low.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, the procedure for assembling a tubular lithium battery is as follows. First, a step of loading the power generating element 1 spirally wound in another step in a battery case 3 through an insulating plate 2 and a lower part of the power generating element 1 are performed. A step of spot-welding the negative electrode lead plate 1a protruding to the inner bottom surface of the battery case 3, and the positive electrode terminal plate 5 with the sealing gasket 4 mounted on the periphery.
Of the non-aqueous electrolyte in the battery case 3 with the step of spot welding the bottom surface of the positive electrode current collector plate 1b protruding above the power generating element 1 and the positive electrode terminal plate 5 positioned at the opening edge of the battery case 3. And a step of covering the opening of the battery case 3 with the positive electrode terminal plate 5, crimping the opening edge of the battery case 3 by curling, and sealing the inside.

In addition to the above steps, in the present invention, an inspection is performed in the welding step as to whether or not the lead plate 1a is normally arranged. In this inspection, as shown in FIG. 2, a lower electrode 10 for spot welding that contacts the bottom surface of the battery case 3, a needle-shaped spot welding electrode 12 that contacts the lead plate 1a, and a lower portion before the welding current is passed. A constant voltage circuit 14 as a power source for supplying a weak constant current between the electrode 10 and the spot welding electrode 12 for a predetermined time, and the constant voltage circuit 14
And a monitor means 16 connected in series with each other, and the acceptance / rejection is judged according to the current value indicated by the monitor means 16. In this inspection, the welding electrode 12 descends when the battery case 3 is installed on the lower electrode 10 and presses the lead plate 1a with the same pressure contact force as during spot welding.
At this stage, a weak current is supplied from the constant voltage circuit 14 for a predetermined period of time, and the monitor means 16 judges pass / fail. If it passes, the circuit is switched to the spot welding power source (not shown), and spot welding is performed. In the present embodiment, the constant voltage circuit 14 for supplying a weak current for inspection is provided separately from the power source for spot welding. However, if the power source for spot welding is shared as the power source for inspection, the constant voltage circuit 14 is The method of the present invention can be carried out without any additional attachment and with almost no modification of the production line.

Next, the following tests were carried out in order to judge whether or not the above inspection method is effective. First, a sheet-shaped positive electrode, a separator, and a sheet-shaped negative electrode are sequentially stacked and wound, and a negative electrode lead plate 1a (Ni, width 5 mm × thickness 0.1 mm) derived from the bottom surface of an electrode group having an insulating plate on the bottom surface is provided. We produced 30,000 samples with an outer diameter of 16 mm and a total height of 33 mm.

Then, a needle-shaped electrode (-) is provided in the central hole of the electrode group.
With a (2 mm diameter chrome copper) plugged in and the bottom surface of the lower part of the battery case supported by the cylindrical electrode (+) (chrome copper having a contact plane of 8 mm diameter), a constant current monitor as a monitoring means was built in. 0.8V was applied to each sample for 0.2msec by the voltage power supply. It should be noted that the pass / fail judgment standard is set based on the preliminary investigation, and the current monitor instruction value is 38
The products with 0 A or more were rejected, and the other products were accepted. For the acceptable product, a negative electrode lead plate 1a was welded to the battery case 3 by applying 2.0 V for 2.0 msec to form a cylindrical battery.

Samples 10 of passed and rejected products
When the monitor current value of each piece was investigated, the acceptable product was 120-
The value fluctuated within the range of 210 A, and the average value was 158 A and the standard deviation was 30.5 A. This value is sufficiently smaller than 380A which was set as the acceptance criterion.

On the other hand, the monitor current value of the rejected product is 3
The value fluctuates between 90 and 420 A, and the average value is 405 A and the standard deviation is 9.7 A, and the fluctuation range is small and exceeds the pass / fail judgment standard of 380 A.

Therefore, the difference between the passed product and the rejected product with respect to the acceptance criteria was clear, and it was judged that the inspection method was sufficiently practical.

Next, 30,000 batteries manufactured through the inspection process of the present invention and 30,000 batteries manufactured without the inspection process of the present invention are respectively inspected by an X-ray inspection apparatus. When the voltage and internal resistance after aging for 20 days after assembly were inspected, the results shown in Table 1 were obtained.

[0019]

[Table 1] In this table, the samples with current monitoring failure were in positions where both lead plates 1a were bent and did not come into contact with the spiral center of the power generating element 1, that is, the tip of the welding electrode 12 at all. Further, in the defect of the conventional product found at the time of the X-ray inspection, the lead plate 1a was similarly bent.

Of the defects found after aging, 252 had a voltage drop due to an increase in internal resistance. This is welding spatter (Cr, Cu
It was found in the subsequent investigation that the main cause was the damage to the separator due to the scattering of powder. It was found that the remaining two had an abnormally high internal resistance, the lead plate 1a had insufficient welding strength, and the inner bottom surface of the battery case 3 was contaminated with an oil film.

Therefore, as is clear from the above table and the results of the investigations below, the inspection method of the present invention is:
A contact failure between the negative electrode lead plate 1a and the inner bottom surface of the battery case 3 can be easily found.

Further, when the negative electrode lead plate 1a is arranged at a substantially regular position with respect to the inner bottom surface of the battery case 3, the tip of the welding electrode 12 makes the lead plate 1a closely contact with the inner bottom surface of the battery case 3. Can be made. And
By applying a weak current before welding, the oil film, oxide film, etc. formed on the surface of the lead plate 1a are removed to obtain a clean welded surface, and spatter is generated in the subsequent spot welding process. It is suppressed, and it is possible to prevent the yield reduction due to the scattering of spatter.

Furthermore, since the inspection can be carried out by using the spot welding equipment, new equipment investment and rearrangement of the production line are unnecessary, which is economical.

[0024]

As described above in detail with reference to the embodiments, in the method for determining the welding work arrangement state of the tubular battery according to the present invention, it is possible to determine the contact resistance between the lead plate as the welding work and the battery case. As the current value changes, the correlation between the current value and the arrangement of the lead plate is checked in advance, and the current value obtained through the monitoring means is compared with the judgment value set in advance to read the lead. It is possible to determine whether the plate is in a proper position with respect to the bottom surface inside the battery case.

Further, when the lead plate is arranged at the proper position, the welding work is performed after the oxide film or the like on the surface of the lead plate is removed by the weak electric current at the time of inspection. The occurrence rate is extremely low, and good spot weldability can be obtained.

Further, since the spot welding equipment can be used for the inspection, new equipment investment and production line rearrangement are almost unnecessary, which is economical.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a cylindrical lithium battery.

FIG. 2 is a cross-sectional view illustrating a method for inspecting a welding position of a lead plate of the lithium battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power generating element 1a Negative electrode lead plate (welding work) 2 Insulating plate 3 Battery case 10 Lower electrode 12 Spot welding electrode 14 Constant voltage circuit (power supply) 16 Monitoring means

Claims (1)

(57) [Claims] 1. A tubular shape formed by bending a lead plate led out to the lower end of a spirally wound power generating element so as to close a through hole formed in the center of the power generating element via an insulating plate. Of the spot welding electrode, which is housed in the battery case, is positioned on the inner bottom of the battery case as a welding work and is in contact with the welding work by being inserted into the through hole of the central portion of the power generation element, and With the other electrode in contact with the battery case, the welding work and the battery case inner bottom portion are clamped and pressed, and in the cylindrical battery formed by spot welding the welding work and the battery case inner bottom portion, the spot A welding power source includes a power source connected between the welding electrode and the other electrode in contact with the battery case, and a current monitoring unit for indicating the current value of the current supplied from the power source. At the stage before performing spot welding by supplying a weak current equal to or lower than the welding current from the power source, the welding work contacts the spot welding electrode in accordance with the current value read by the monitor means. A method for determining a welding work arrangement state of a cylindrical battery, comprising determining whether or not the welding work arrangement state is arranged at a position.