JPS6038828B2 - Cell-to-cell connection method for lead-acid batteries, pole poles for cell-to-cell connection, and electrodes for resistance welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to lead-acid batteries, and relates to a highly reliable inter-cell connection method with excellent mechanical, electrical properties and liquid tightness.

Several methods have been used in the past for cell-to-cell competition in lead-acid batteries, but in the case of automobile batteries, the through-cell method is currently becoming mainstream in order to reduce battery weight, improve performance, and reduce costs. be.

As the name suggests, the through-type connects the electrode plates between the phosphoric cells by passing through the partition wall, and the connecting part between the cells is shorter than the conventional partition-over type. Therefore, the voltage characteristics are improved and the amount of lead used can be significantly reduced. FIG. 1 is a cross-sectional view showing the through-type cell-to-cell connection, in which the pole posts 2, 2' to which the plurality of pole plate ears 1, 1' constituting the pole plate group are welded, The connection is made through the partition wall 4 between the cells 3 and 3'. Methods such as resistance welding and gas welding are used to connect the pole posts 2 and 2', but resistance welding is often used because it is particularly excellent in mass production. FIG. 2 shows the state of through-type cell-to-cell connection using resistive heating.

First, the pole pillars 2 and 2' in the adjacent cells 3 and 3' are brought into contact through the circular through-hole 5 provided in the partition wall 4, and a pair of welding electrodes 6 are brought into contact with this, as shown by the thick arrows. While applying pressure P in the same manner as above, the material to be welded is removed from one electrode 6.
That is, the welding current 7 is passed through the pole posts 2, 2' to the other electrode 6. By this operation, a portion of the pole columns 2, 2' is melted at the contact surface 8 of the pole columns 2, 2' due to resistance heat generation due to contact resistance and electric resistance of the pole columns themselves. Then, as the current supply ends, the temperature of the welded part decreases, the molten part solidifies, and welding is completed. Figure 3 shows a cross section of the connection after good welding, but as mentioned above, some of the poles are melted and solidified on the contact surface 8 of the poles 2 and 2'. A nugget 8' produced by this process is recognized. There are three main characteristics required of the connection part in the resistance welding connection method.

The first is a sufficient contact area (
(area after melting) must be ensured. Second, liquid tightness must be ensured so that electrolyte does not move between adjacent cells 3, 3' through the connection portion. Thirdly, it must have sufficient mechanical strength so that the welded portion will not be destroyed by vibration or the like. In order to obtain a joint that satisfies these various characteristics, advanced welding technology is required, but the most difficult problem is how to prevent the occurrence of "splashing". As is well known, the material of the pole pillar is pure lead or a lead-based alloy containing a small amount of alloying elements (Pb-Sb system,
(Pb-Ca system, etc.), both of which are 250 to 33,000
It has an extremely low melting point among metal materials. At first glance, this tends to be thought to make welding easier, but this is not appropriate in the case of welding that involves extremely steep heating, such as resistance welding. In other words, the temperature of the contact surfaces of the pole pillars rises above the melting point almost as soon as the current starts flowing, and the temperature of the molten metal rises above its boiling point (approximately 1700℃).
It gets heated even more. Because such extreme heating occurs in a very short period of time, the molten metal undergoes significant volumetric expansion, and as a result, it flies out from the contact surface under a very large pressure. This kind of scattering of molten metal is called "splatter", but lead or lead alloy (hereinafter abbreviated as lead alloy)
In the case of
is likely to occur. In resistance welding, the electrode pressurizing force has the role of pressing down the unmelted portion on the outer periphery of the molten metal and preventing the molten metal inside from flying out as described above.

Therefore, it should be possible to prevent the occurrence of "scattering" by increasing the pressure, but in this case as well, the inherent properties of the lead alloy pose a major obstacle. In other words, lead alloy, which is soft even at room temperature, becomes even softer as the temperature rises during welding. For this reason, during welding, the electrode may significantly dig into the inside of the pole column, causing the pole column itself to deform abnormally, and the contact surfaces of both pole columns to open during welding, which causes expulsion. This tendency becomes more pronounced as welding is carried out with a large current in an attempt to obtain a large connection area (welded area or nugget diameter) in one welding process, as has been done in the past. Such abnormal deformation disturbs the current path during welding while energizing, causing problems such as melting of parts that should not originally be melted, and further promoting the occurrence of "splintering". Become. Now, the biggest reason why the occurrence of the above-mentioned "scattering" is considered to be a big problem is as follows.

In other words, as mentioned above, the true nature of the "scattering" is a part of the scattered pole pole, which is naturally a good conductor of electricity, and the connection between the cells is that the pole plate group connects to the cell as shown in Figure 2. This is done after the welding has been inserted, and if the "spatter" generated during welding flies into the cell, it may cause a short circuit between the poles.
Significantly shorten battery life. For this reason, “
The occurrence of ``scattering'' must be suppressed as much as possible. Also, if you understand the process of ``scattering'', it becomes clear that ``scattering''
When this occurs, welding defects are likely to occur, large blowholes occur, and a sufficient nugget area cannot be secured. In such a state, the three characteristics required of the connection part described above are no longer fully satisfied, and a highly reliable connection part cannot be obtained. As mentioned above, in the conventional through-type connection using resistance welding, "dispersion"
This is an extremely serious problem, and it is difficult to find a good solution. Therefore, it is difficult to fully utilize mass production, which is the biggest advantage of the resistance welding method, by using tweezers to remove the "scattering" that scatters inside the cell after welding is completed. We have been producing in a state where we cannot make the most of it. The present invention solves the above-mentioned problems and provides a resistance welding method to obtain a highly reliable connection. The content of the present invention will be described below.

The key point of the present invention is to prepare a pole pole having a joint shape effective in preventing the occurrence of "splash".

Next, pre-energize the prepared pole pole placed at a predetermined position, form a thermocompression bonded part on the outer periphery of the nugget generated by main energization, and ensure close contact between the partition wall and the pole pole. This suppresses the occurrence of "scattering" during main energization,
At the same time, ensure liquid tightness. Next, main energization is performed to form a nugget of a predetermined size at the connection portion, thereby ensuring a tight twill portion having sufficient mechanical strength to withstand the aforementioned large current discharge. FIG. 4 shows the shape of the joint of the pole column used in the present invention.

In the figure, reference numeral 9 denotes a pole pole, and a disc-shaped protrusion 10 is formed on the surface of this pole pole to be welded (the surface that contacts the pole pole of an adjacent cell). Furthermore, this disc-shaped protrusion 10
The surface consists of a circular uneven part 11 located at the center and having minute unevenness, and a smooth ring part 12 surrounding the circular uneven part 11. Details of these are shown in Figure C). That is, the height W of the disc-shaped protrusion 10 is 1/2 of the thickness of the partition wall 4.
slightly smaller than The diameter D is almost equal to the diameter of the circular through hole 5 provided in the partition wall. Further, it is preferable that the tips of the fine irregularities in the circular irregularities 11 do not protrude from the surface of the smooth ring part 12, but are rather retracted slightly from the surface. The size of the diameter D2 is determined in relation to the size of the nugget required for the connection portion. Furthermore, a circular concave portion 13 is similarly provided on the back surface of the circular concavo-convex portion 11 . This recess 13 is provided to reduce the heat capacity of the disc-shaped protrusion 10 and to facilitate resistance welding by main energization. The center of the recessed portion 13 is located at the same position as that of the circular uneven portion 11, and its diameter D3 is the same as or slightly larger than D2. Further, the depth W2 is determined to be convenient for the generation of nuggets during main energization. Next, details of a method of resistance welding a pole column having the above-mentioned joint shape will be described.

The resistance welding method according to the present invention is carried out in two steps: preliminary energization and main energization, as described above.

FIG. 5 shows the first stage (preliminary energization stage) of the welding process. Pole columns 9, 9' having the above-mentioned joint shape
(9 and 9' have the same joint shape) are brought into contact with each other so that their respective smooth ring portions 12 face each other as shown in the figure, and a pre-energization electrode 14 having a shape as shown in FIG. 6 is brought into contact from the outside. The preliminary energization electrode 14 is provided with a link-shaped protrusion 15, and as shown in FIG. It is brought into contact with a position 17 opposite to the portion 12. After positioning in this manner, an electrode pressing force P is applied to bring the pole columns 9, 9' into close contact and preliminary energization is performed. The current at this time is not large enough to melt part of the pole columns 9, 9'. The welding current 7 flows in a concentrated manner in the smooth ring portions 12 of the pole posts 9, 9' as shown by the arrows. This is because the circular uneven portion 11 at the center of the disc-shaped protrusion 10 of the pole pillars 9, 9' has minute unevenness, and the resistance to the welding current in this area is large, and the pre-energization This is because the electrode 14 has a shape that concentrates the welding current on the smooth ring 12. In this way, a relatively small current is applied for a longer time than the main energization, and a slow temperature rise causes the smooth ring part 12 and the partition wall 4 and pole pillar 9 around it to become energized.
, 9' is raised to 150-200 qC. Through this operation, the bipolar columns 9 and 9' are joined in a thermocompression state at the smooth ring portion 12, and the electrode pressing force P,
As a result, the partition wall 4 and the pole pillars 9, 9' are in close contact with each other.
In this way, the periphery of the circular uneven portion 11 where a nugget is to be formed by the main energization is brought into a thermocompression bonded state by the above-mentioned preliminary energization, creating a state in which the occurrence of "scattering" during the main energization can be mechanically suppressed. At the same time, at this stage, the liquid-tightness of the connection portion described above is ensured. The pre-energized connection section is then subjected to main energization as a second step.

The main energization is performed using a welding electrode different from that used in the first stage preliminary energization. Figure 7 shows the shape of the electrode used for main energization.
Show the structure. The main energizing electrode 18 has an electrode chip 19 on the main body.
, has a structure in which a pressure ring 20 surrounding the electrode tip 19 is attached. Pipes 21 and 22 through which cooling water flows to cool the electrode chip 19 are provided in the center of the main body. Further, although the electrode chip 19 is screwed to the main body, a pipe 23 for introducing cooling water is also provided inside the electrode chip 19, and this is connected to the pipe 22 on the main body.
It is processed to connect with. In addition, the electrode tip 19
The shape of the tip 24 is preferably conical to achieve uniform current distribution over the weld. death,. The welding current in the main energization is supplied from this electrode tip 19 to the pole posts 9, 9'. The pressure ring 2 disposed around the outer periphery of the electrode tip 19 has a U-shaped cross section as shown in FIG. 7C, and a ring-shaped spring case 25 also has a U-shaped cross section. It is combined with The pressure ring 20 can be displaced as shown by the arrow (H) by a spring 26 housed in a spring case 25. It is electrically insulated from the current-carrying electrode 18, so that the welding current does not flow through the pressure ring 20', but instead passes through the central electrode tip 19 to the pole columns 9, 9.
’. FIG. 8 shows a situation in which main current application is performed using the main current application electrodes as described above.

Prior to energization, the main energization electrode 18 described above is connected to the poles 9, 9.
′, the electrode tip 19 is located in the circular recess 13 of the pole posts 9, 9′ in a position opposite to the smooth ring portion 12 of the pole posts 9, 9′ (which is in a thermocompression bonded state due to preliminary energization). The pressure ring 20 is positioned so as to be in contact with the surface 17.
Next, electrode pressurizing force P2 is applied as shown by arrow (0).
As a result, the opposing circular concavo-convex portions 11 of the pole posts 9, 9', which were not welded during the first preliminary energization, come into contact with each other suitable for forming a nugget. At the same time, the pressurized IJ ring 20 receives the repulsive force of the compressed spring 26 from the smooth ring portion 12 and the close contact portion between the partition wall 4 and the pole pillars 9, 9', which were in a thermocompression bonded state in the first stage.
Preparations are made to ensure that the state brought about by the preliminary energization in the first stage is sufficiently maintained during the main energization in the second stage. In this state, welding current for main energization is applied. The welding current 7 flows concentratedly in the circular uneven portion 11 as indicated by the arrow shown in FIG. As mentioned above, since the pressurizing ring 20G is electrically insulated from the current-carrying electrode 18, the smooth ring portions 12 of the pole columns 9 and 9' are bonded by thermocompression in the first stage, and the electricity in this portion is Even if the resistance is extremely small, there is no need to consider diverting the current to this part. Note that, as described above, the circular uneven portion 11
is a part processed to have minute irregularities.
Therefore, when the pressurizing force P2 is obtained, the circular uneven portions 11 of the pole columns 9 and 9' come into contact with each other in a state of close contact, but as mentioned above, the fine unevenness on the surface When viewed microscopically, there is a fairly partial contact state. This means that this part has an appropriate contact resistance, and combined with the fact that the electrode arrangement shown in Figure 8 allows effective current concentration, a relatively small welding current can be used. Heat is generated over the entire area of the circular uneven portion 11 to generate a nugget of sufficient size. If the welding current is small, abnormal deformation of the pole pillars 9, 9' can be prevented, and the resulting disturbance of the current distribution is also eliminated, so nuggets are generated in areas where they should not be generated, and this causes "scattering". may never occur. Moreover, if such a welding method is used, the ring-shaped thermocompression bonded part 28 generated by preliminary energization
Since the contact portion 29 between the partition wall 4 and the pole pillars 9, 9' is held with sufficient force by the pressure ring 20', this portion will not be destroyed during main energization, and these portions Because the outer circumference of the nugget generated during main energization is completely suppressed by the presence of the nugget, the occurrence of "scattering" is sufficiently suppressed. As described above, by applying the resistance welding method of the present invention to a through-type connection, the occurrence of "splashing" can be sufficiently suppressed, and it can sufficiently withstand large current discharge.
A highly reliable connection having sufficient liquid tightness and mechanical strength can be obtained.

Next, examples of the present invention will be described.

In order to confirm the effects of the present invention, a comparative experiment was conducted with a conventional resistance welding method (hereinafter referred to as the "conventional method").

The effectiveness was confirmed by comparing the occurrence of "splashing", liquid tightness, weld traverse time under large current discharge (100 ships), and weld strength with the conventional method. Since it is difficult to directly evaluate the occurrence of "explosion," we quantitatively assessed the occurrence of blowholes in the nugget, which is closely related to the occurrence of "exfoliation." The dimensions and shape of the welding electrode in the conventional method are as shown in FIG.

Further, the dimensions and shape of the pole-column joint used in the conventional method are as shown in FIG. On the other hand, FIG. 11 shows the dimensions and shape of the pole-column joint according to the method of the present invention.

In addition, in FIG. 11, the circular uneven portion 11 is 0.2~
It is knurled to a depth of 0.3 ribs. Also,
Figure 12 shows the dimensions and shape of the preliminary energization electrode used in the first stage, that is, preliminary energization, and Figure 13 shows the dimensions and shape of the main energization electrode used in the second stage, that is, main energization. . In addition, the material of the welding electrode in both the conventional method and the method according to the present invention is a 1% Cr-Cu alloy.

In addition, in the comparative experiment, the same container was used for both methods. The thickness of the bulkhead of the open tank is 1.65 ribs.
The diameter of the through hole provided in the partition wall is 18 mm. In addition, the material of the pole pillar is Pb-3%Sb-0.3%
It is a hanging alloy. Table 1 shows welding conditions when connecting by the conventional method and the method according to the present invention. The welding device used was an AC type welding device with a rated capacity of 100 KVA, a maximum current of 30,000 A, and a maximum pressing force of 400 kg.

The experimental results are shown in FIG. 14 and Table 2.

From these results, it can be seen that the method according to the present invention is extremely superior. Table 1 Table 2 Note) 1 Liquid tightness is determined by penetration test 2 Large current discharge is current 1000A 3 Welding strength is torque value

[Brief explanation of the drawing]

Figure 1 shows the state of the through-cell connection in an automotive lead-acid battery, where a is a side sectional view, b is a sectional view taken along line A-A' in a, and Figure 2 is a conventional resistance welding method. FIG. 3 is a cross-sectional view showing the state of the connection after resistance welding is completed, and FIG. 4 is a cross-sectional view showing the joint shape of the pole column used in the connection method according to the present invention. , a is a front view, b is a sectional view taken along line B-B of a, c is an enlarged view showing the details of the circled part of b, and FIG. 5 is a connection method according to the present invention during preliminary energization. 6 shows the shape of the preliminary energization electrode used for the preliminary energization, a is a front view, b is a side view, and FIG. 7 is a sectional view showing the connection method of the present invention. This shows the actual current-carrying electrode used when applying current, a is a side view, b is a front view, c and b are cross-sectional views taken along line C-C', and Figure 8 is a main current-carrying electrode used when applying current. FIG. 9 is a cross-sectional view showing the situation in which current is applied. FIG. Figure 10 shows the dimensions and shape of the joint part of the pole pole similarly used in the conventional method, where a is a side view, b is a front view, and Figure 11 is the dimensions and shape of the joint part of the pole pole used in the embodiment of the present invention. The shapes are shown, a is a front view, b is a side view, c is a sectional view taken along the line D-○ of a, and FIG. 12 is the dimensions and shape of the preliminary energization electrode used at the time of preliminary energization in the embodiment of the present invention. , a is a side view, b is a front view,
Figure 13 shows the dimensions and shape of the main current supply electrode used in the main power supply, where a is a side view, b is a front view, and Figure 14 is a blow that occurred at the bush joint in the embodiment of the present invention and the conventional method. FIG. 3 is a frequency distribution diagram of the area of holes. 4 is a partition wall, 5 is a through hole, 7 is a welding current, 9 and 9' are pole columns, 10 is a disc-shaped protrusion, 11 is a circular uneven part, 12 is a smooth ring part, 13 is a recessed part, 14 is a preliminary energization 15 is a ring-shaped protrusion, 18 is an electrode for main current supply, 19 is an electrode tip, 20 is a pressure ring, 21, 22, 23 are pipes, 2
4 is the tip of the electrode tip, 25 is a spring case, 26 is a spring, 28 is a thermal eaves portion, and 29 is a contact portion. Figure 1 Figure 2 Figure 3 Figure 4 Hakama 5 figure Sei 6 Hakama figure 8 Figure 9 Crocodile 10 Figure 11 Figure 12 Figure 13 Figure 14

Claims (1)

[Scope of Claims] 1. A circular shape having a diameter that allows it to be inserted closely into a through-hole provided in a partition wall, and a height that allows the other part to come into close contact with the partition wall when inserted into the through-hole, and whose surface is minutely uneven. A disk-shaped protrusion consisting of an uneven portion and a smooth ring surrounding the circular uneven portion, and a pair of pole columns each having a concave portion on the back surface of the circular uneven portion are arranged such that the disk-shaped protrusion faces each other at the through-hole. The process of arranging the poles on both sides of the partition wall is followed by thermocompression bonding the smooth ring parts of the pair of pole pillars by applying a preliminary current so as to concentrate the welding current on the smooth ring parts while pressing them together. At the same time, the process of bringing the contact part of the pole pillar and the partition wall into a close contact state,
Further, the smooth ring part in a heat-compressed state is pressed and held in an electrically insulated state, and the main current is applied so as to concentrate the welding current on the circular uneven parts of the pair of pole pillars to melt and contact the parts to form a nugget. A method for connecting cells of a lead-acid battery, characterized by the following. 2. A circular uneven portion with minute irregularities on its surface, which has a diameter that allows it to be inserted closely into the through-hole provided in the partition wall, and a height that allows the other part to come into close contact with the partition wall when inserted into the through-hole, and the circular unevenness. A pole column for connecting between cells, comprising a disc-shaped protrusion section including a smooth ring section surrounding the section, and a concave section on the back surface of the circular uneven section. 3. A circular concavo-convex portion with minute irregularities on its surface, which has a diameter that allows it to be inserted closely into the through-hole provided in the bulkhead, and a height that allows the other part to come in close contact with the bulkhead when inserted into the through-hole; A disc-shaped protrusion consisting of a smooth ring surrounding an uneven part and a pair of pole pillars each having a recess on the back surface of the circular uneven part are placed on both sides of the partition wall so that the disc-shaped protrusion faces each other at the through-hole. Next, while pressing the smooth ring parts of the pair of pole posts together, preliminary energization is applied so as to concentrate the welding current on the smooth rings, and the smooth ring parts are bonded together by thermocompression, and the pole posts and the partition wall are The step of bringing the contact portions into a close contact state, and further applying main current to concentrate the welding current on the circular uneven portions of the pair of pole columns while pressing and holding the smooth ring portions in a thermocompression bonded state in an electrically insulated state. In the resistance welding electrode used in the cell-to-cell connection method of lead-acid batteries, which consists of a process of melting the parts and making a nugget, it is used in the final main energization process and is brought into contact with the recesses of the pair of pole columns from both sides of the partition wall. A resistance welding electrode comprising an electrically insulated pressure ring surrounding an electrode tip, the pressure ring being elastically displaceable in its axial direction.