JPS607058A - Method of welding terminal for current collection - Google Patents

Abstract

PURPOSE:To enable a current collector terminal, having a protruding section radially extending from its center to its periphery, to be connected to the end of a rolled electrode for a Ni-Cd battery or the like at a plural number of points by placing the current collector terminal on the end of the electrode before a laser beam is irradiated. CONSTITUTION:A current collector terminal 2 has a continuous protruding section 4 radially extending from its center toward its periphery and having a pointed end with an angle of 90 deg.C or below. It is placed on the end 3 of a plate 1 for a Ni-Cd battery or the like which is formed by rolling a positive plate, a negative plate and a separator so that the pointed end of the projection 4 closely touches a core member 5 extruding from the end of the plate 1. After that, a laser beam or an electron beam is irradiated along the center line of the projection 4 so as to connect the terminal plate 2 and the plate 1 electrically at a plural number of points (a-e). As a result, the thermal imbalance between the terminal 2 and the plate 1 is compensated greatly improving welding intensity, thereby enabling multipoint current collecting to be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a battery having a structure in which a wound electrode plate is housed in a container, such as an N1-CD battery. ).

As everyone knows, it is a portable power source for electrical and electronic devices. That is, it is required that the drop in battery voltage be as small as possible when discharging with a large current, and for this purpose it is essential to reduce the internal resistance of the battery as much as possible.

As one means of solving this problem, a so-called multi-point current collection system has been adopted. This differs from the conventional method in which 4-3 current collecting terminals are placed at one location on the electrode plate and the current generated inside the plate is collected there. In this method, the distance that the generated current takes to reach the current collecting terminal is shortened, and as a result, the internal resistance of the battery can be reduced.

FIG. 1 shows an example of the connection state between the current collecting terminal and the electrode plate when the point current collecting method is used. In the same figure 1
is an electrode plate, and this electrode plate l is overlapped with a mating diameter (for example, if l is an anode plate, the mating diameter becomes an anode plate) via a separator, and is wound as shown in the figure. (The separator and the other electrode are not shown in the figure.) Also, 2 is the current collecting terminal.
As shown in the same figure, this is located on a plane formed by the end 3 of the wound electrode plate 1, for example, a projection 4 formed on the current collecting terminal 2 and the end of the electrode plate 1. It is electrically connected to part 3 (strictly speaking, the end of the core material constituting electrode plate 1) by means such as welding (a-, -e in the figure), and current is collected from this part. It is.

Now, the object of the present invention is a method of connecting the current collecting terminal 2 and the electrode plate 1 described above. Resistance welding has conventionally been used for this connection, but this type of welding is not necessarily easy, and the welding strength often varies significantly and is often unreliable. The reason is as follows.

FIG. 2 shows in more detail the connection between the current collecting terminal 2 and the electrode plate 1 shown in FIG. That is, the electrode plate 1 has a structure in which the active material 6 is held by the core material 5, and the end portion 3 of the electrode plate 1 described above is formed as shown in the figure.
A portion of the core material 5 that slightly protrudes from the portion where the active material is present is connected to the current collecting terminal 2.

In the case of Ni-Cd batteries, the core material 5 is usually a punched metal made of PE with N1 plating on the surface, and the opposing current collecting terminal 2 is also made of almost the same material. The first problem here is the thickness of both parts. Core material 5 generally has a thickness of 50 to 80 μm
In contrast, the current collecting terminal 2 should have a thickness of 0.15 to 0.2 mm, considering that the current from the entire plate is collected here. used. Based on this difference in wall thickness between the two (the difference in heat capacity of the welded part can be said to be fatal for making a good welded part), the contact area between the two is extremely small and the heat capacity is Otherwise, even if welding current flows, the temperature rise at the protrusion 4 of the current collecting terminal 2 will be slight, and we cannot expect that part of it will melt.On the other hand, the opposite is true for the core material 5, which has a small heat capacity. The melted metal will melt more than necessary.
If the surface of the protrusion 4 gets wet, welding will be completed, but
Since the temperature rise of the protrusion 4 is slight, it may not be wetted by the protrusion 4, or even if it is wetted, the welding will not be successful as a result. Also, in this welding, the first
As seen in the figure, one protrusion 4 is numerous (a%
It must be welded to the electrode plate 1 at position e), but since there are variations in the contact state between the two before the welding current is applied and series type welding has to be performed, the current that is ineffective for welding is transferred to the current collecting terminal 2. The problem has been that less than half of the number of welding points that actually need to be welded are welded due to irregular fluctuations in the effective current flowing through the welding.

The present invention solves the above-mentioned problems and has excellent strength and electrical properties. This provides a highly reliable connection.

Next, details of the present invention will be described. The main point of the present invention is to compensate for the thermal imbalance in the welding zone due to the difference between the heat capacity of the current collecting terminal 2 and that of the core material 5 of the electrode plate 1 by using a welding heat source with high energy density. and the application of the new welding method, thereby making it possible to obtain welds of excellent quality by eliminating the disadvantages associated with the shunting of the welding current peculiar to series type resistance welding. There is one.

That is, a laser beam or an electron beam is used as a heat source for welding. As is well known, laser light is essentially a light with very good properties and has a waveform with a different phase. Therefore, if this laser light is focused using a lens or a concave mirror, an extremely high energy density can be achieved in an IC. It will be done. The same is true for electron beams, and a similar state can be obtained by focusing them with a magnetic lens in a vacuum.

For both, an energy density of about 10'W/c, -m can be obtained, or this value is, for example, 108 to 4 W/d of the arc.
It can be seen that this value is significantly larger than that of .

Therefore, it is used as an extremely effective heat source, for example, for melting W, which has a melting point of 3000° C. or higher. In addition, since each type of heat source can be condensed to an extremely small diameter, it is an extremely effective heat source for heating only an extremely small area to a predetermined temperature where necessary. If such a heat source is used, it is possible to heat the current collecting terminal 2, which has an extremely large heat capacity compared to the tip of the core material 5, to an appropriate temperature, and the core material 5 can also be heated to an appropriate temperature. It is also possible to achieve a heat balance suitable for welding that does not cause melting. In addition, in the case of resistance welding, a considerable amount of current that does not contribute to welding flows inside the current collecting terminal 2 due to the shunting effect, which causes an abnormal temperature rise in areas unrelated to welding, which can lead to welding with the welding electrode. happens,
In the case of Kerr laser welding or electron beam welding, in which localized melting occurs, the above-mentioned disadvantages can be eliminated because local heating of minute areas can be performed.

However, both laser welding and electron beam welding are not without problems. It is a problem of contact between the materials to be welded. In other words, as mentioned above, when using a heat source with high energy density such as single welding or electron beam welding,
Since only the necessary parts are welded without exerting a heat influence on unnecessary places, for example, even if a part of the material to be welded melts, the area will be extremely small. For example, if there is a gap between the materials to be welded, there is often not enough molten metal to fill the gap. Therefore, when using this type of welding method, it is necessary that the materials to be welded be in close contact with each other at the location to be welded.

For this purpose, a protrusion is usually provided on the current collecting terminal side as in the case of resistance welding. Of course, even if the current collecting terminal is planar, as mentioned above, the contact between the current collecting terminal 2 and the wound electrode plate core material 5 is uniformly tight at the part to be welded. Although it is not necessary if there is a protrusion, it is wise to provide a protrusion because the winding accuracy is often not so good.

Although the shape and dimensions of the protrusions require some consideration, 1 For example, as shown in Figure 1, it is easier to weld if the protrusions extend radially from the center of the current collecting terminal 2. That seems to be the most preferable option. This is because the contact area between the current collecting terminal 2 and the tip of the core material 5 of the electrode plate 1, that is, the area to be welded, is located at the center of this radially extending protrusion 4. For example, as shown in FIG. By scanning the electron beam or laser beam along the center line of the protrusion 4 as shown by the arrow, the tips of all the electrode plate core materials 5 below the protrusion 4 can be welded at once. It is from. Also, how many protrusions 4 extend radially?

In the case of resistance welding, the number of branches of welding current is limited to as little as possible (1), and the limit is about four, but in the case of laser welding or electron beam welding, there is no need to limit it in particular. It goes without saying that more is better in terms of current collection performance, but this number is determined after considering the required welding strength, manufacturing cost, etc. Also, the sharpness of the tip of the protrusion must be carefully considered. Naturally, during welding, the current collector terminal 2 is pressed into contact with the tip of the electrode plate core material using an appropriate jig, and then the laser beam or electron beam is irradiated. However, the pressing force at this time must be such that it does not cause abnormal deformation to the tip of the core material 5. According to our study results, it is not appropriate to apply a pressure of 5 to 6 or more. Then, under a pressure of
In order for the two to be in close contact,
When the unevenness formed by the tip of the core material 5 is ±01 to 0.2 mm or less.

It has become clear that the angle formed by the tip of the projection 4 (α in FIG. 3) needs to be 90° or less.

Next, examples of the present invention will be described. With regard to the connection between the Hr-cd battery electrode plate 1 and the current collector terminal 2, welding conditions were compared between welding by the method according to the present invention and welding by the conventional resistance welding method. The same electrode plate was used in each case for the comparative experiments, but the core material 2 was made of Fe with a thickness of 80 μm, and the surface was coated with 7 to 8 μm of Ni.
It is plated. Note that the number of turns of the electrode plate 1 is 6 turns. Next, regarding the current collecting terminal 2, there are differences in the dimensions, shape, and number of protrusions 4 between the welding method according to the present invention and the conventional method, but other aspects are the same. In other words, the material is C
The outer diameter of the circular part is 19 mm, and the dimensions of the current collecting part 7 are 81 nm wide, 13 mm long, and thick. is 0
There are two issues.

In each case, the projections 4 provided on the disc part were designed to extend radially from the center toward the outer periphery (see Figures 1 and 3), but the number of projections 4 was 4 in the conventional method (see Figures 1 and 3). In order to minimize the shunt effect during resistance welding (determined after confirming that this is the most advantageous number for stopping the welding), this number was set at 6 in the method according to the present invention 1. Also, the tip of the protrusion 4 The angle I is 75° in both the conventional method and the method according to the present invention.

Next, regarding the welding conditions, in the case of the conventional method, a capacitor discharge type welding power source is used, and the electrode is Cr-C with a diameter of ψ5.0.
Use one manufactured by u, electrode spacing (center distance 11L4mm)
Welding was carried out using an electrode pressure of 50 and a welding energy of 180 W8. In the case of the method according to the invention laser welding was applied. The light source is CO, gas laser is used, and the beam diameter is y30.
．． 5 mm, and a beam was applied to the center of the protrusion 4 from the center of the current collecting terminal 2 toward the outer periphery using welding energy of 50 Joule.

I scanned it and welded it.

Fifty samples were each made by welding in this manner, and the current collecting terminal 2 was peeled off by bending the current collecting part 7 vertically, grasping this part, and pulling it. The load was measured and the superiority and inferiority of the two-center contact method was compared. The results are shown in Table 1. As is clear from the results (1) If the method according to the present invention is used, the welding strength itself is greatly increased, and the variation, which is the most important thing for mass-produced products, is reduced, and reliability is extremely improved.

Table 1 Although the experimental results for electron beam welding are not listed in the main text, we conducted a similar comparative experiment and found that
It should be noted that the results were similar to those of Habo laser welding.

As described above, according to the present invention, in a multi-point current collection type battery, the welding strength between the current collection terminal and the electrode plate end is significantly improved by one point, and the variation is also small (IT reliability is improved). It has great industrial value.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the main parts showing the connection state between the current collecting terminal and the electrode plate in one N1-CD battery that adopts the multi-point current collecting system.
Fig. 2 is a detailed explanatory diagram of a partially enlarged view of Fig. 1, and Fig. 3 shows an example of the shape of the current collecting terminal used in the method of connecting the current collecting terminal and the electrode plate according to the embodiment of the present invention. In the figures, (a) is a top view, (b) is a side view, and (cl is an enlarged view of part A in (bl). 1 is an electrode plate, 2 is a current collecting terminal, and 3 is an end of the electrode plate. 4 is the protrusion, 5 is the core material (Figure 1, Figure 3)

Claims (1)

[Scope of Claims] The end portion 1ζ of the wound electrode plate is brought into contact with the current collecting terminal, and the current collecting terminal and the end portion of the electrode plate are electrically connected at a plurality of points. In batteries with multi-point current collection system. The current collecting terminal is provided with a continuous projection extending radially from the center to the outer periphery and having a tip angle of 90° or less, and the tip of the projection and the end of the electrode plate that is the constituent material of the electrode plate are provided. The current collecting terminal and the electrode plate are connected by bringing the exposed tip of the core material into close contact and then irradiating the center of the protrusion with a laser beam or an electron beam. Welding method for current collector terminals.