JPH023267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sealed lead-acid battery, and particularly to an improved safety valve thereof.

Conventional structure and problems Sealed lead-acid batteries are widely used as a small, portable power source because the glass mat that is the separator holds the electrolyte and does not flow, so the electrolyte does not overflow outside the battery container. There is.

Sealed lead-acid batteries have a structure in which oxygen gas generated at the positive electrode plate during charging is absorbed into the negative electrode plate, so that gas usually does not escape to the outside of the battery. However, when charging with a large current, the amount of oxygen gas generated by the positive electrode plate is greater than the oxygen gas absorption capacity of the negative electrode plate, and hydrogen gas is also generated from the negative electrode plate, so if the battery is completely sealed, becomes quite high pressure. Therefore, a safety valve is provided that opens when the internal pressure of the battery increases. Generally, this type of safety valve has a structure in which a rubber valve 1 is placed over a valve cylinder 2 as shown in FIG. However, with such a rubber valve structure, it is difficult to mechanize the fitting of the rubber valve 1 into the valve barrel 2, and the reality is that the fitting is done manually by a person after pouring the electrolyte into the battery case 3. Not only does this type of safety valve increase manufacturing costs because it takes many man-hours to assemble, but the material cost of the rubber valve itself is higher than the synthetic resin used in the battery case, making the raw material cost relatively high. Put it away.

Furthermore, the process of inserting the electrode plates into the battery case is difficult to mechanize, which poses a problem in mass production.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
By using a film-shaped or sheet-shaped battery case and also molding the safety valve integrally with the battery case, we are able to provide a sealed lead-acid battery with a structure suitable for mass production that is easy to mechanize, reducing manufacturing costs, and at the same time saving materials. The purpose is to reduce costs.

Structure of the Invention The present invention involves sandwiching an electrode plate group consisting of a positive electrode plate, a negative electrode plate, and a separator between two film-like or sheet-like synthetic resin bodies that are acid-resistant and heat-sealable, and surrounding the electrode plate group. The synthetic resin body is thermally welded leaving one unwelded part to create a sealed part and used as a battery case, and the unwelded part opens when the internal pressure of the battery is higher than the outside air pressure (when pressurized). A safety valve is constructed by aligning the above two film-like or sheet-like synthetic resin bodies in parallel with almost no gap, so that the gas is released from the gap when the pressure is low (when the pressure is reduced), and the valve closes to seal the gap. It is characterized by having the function of

The valve opens when the battery is pressurized for safety reasons, and the valve closes when the battery is depressurized to prevent self-discharge from progressing when the negative electrode plate reacts with oxygen in the atmosphere when the battery is stored in a charged state. This is to prevent this. After a while after charging is completed, the oxygen generated from the positive electrode plate and remaining inside the battery is absorbed by the negative electrode plate, and the inside of the battery becomes depressurized. When the pressure is reduced, the unwelded parts contract, and the gap completely closes, creating a sealed state.
The inside of the battery is designed to be isolated from the outside air.

Description of Examples Examples of the present invention will be described below. In Figure 2, the electrode plate group 6 consisting of one positive electrode plate (length 50 mm x width 70 mm x thickness 3.0 mm), two negative electrode plates (length 50 mm x width 70 mm x thickness 1.3 mm) and a glass mat separator is made of heat-resistant material. In addition, it is sandwiched between two 0.3mm thick heat-sealable polyethylene films or sheets.
Out of the periphery of the electrode plate group 6, only the bottom and left and right sides are heated from the outside at 150° C. for about 1 minute using a heat press, and the polyethylene is welded together to form a welded part 5 and a battery case 8, Inject the specified dilute sulfuric acid electrolyte from the unwelded upper part. After pouring the liquid, heat press the upper part again under the same conditions to seal the pole pillar 7, and at the same time form one unwelded part 4 where two films or sheets of polyethylene face each other in parallel with almost no gap. Then, the battery case 8 was completed by creating a sealing part surrounding the electrode plate group. This unwelded part opens when the internal pressure of the battery is higher than the outside air pressure (when pressurized) and releases the gas generated from the electrode plate group through the gap, and conversely closes when it is lower (when pressure is reduced). It functions as a safety valve by sealing the gap.

In this structure, the conditions for further improving the function as a safety valve, especially the airtightness during depressurization, are as follows.

When it comes to synthetic resin materials, polyethylene and polypropylene are softer than AS (acrylonitrile-styrene copolymer) or ABS (acrylonitrile-butadiene-styrene copolymer) resins, which allow internal gas to be discharged more easily and are also airtight. I found out something good. This also relates to the thickness of the resin, and the thinner the resin, the more the same can be said.

Next, the unwelded parts, that is, the synthetic resin parts facing each other in parallel, have a narrower unwelded width and a longer distance, the better the airtightness.

However, when the battery is in a pressurized state, making the width extremely narrow may cause too much internal pressure and damage the battery, so it is better to lengthen the distance with an appropriate width. Creating a maze shape to increase the distance improves airtightness. In other words, Fig. 2, Fig. 3 a, b
As shown in FIG. 3, by providing a thermally welded portion 5a that partially blocks the gas passage in the unwelded portion, the substantial gas discharge distance can be increased. This type of thermal welding can be easily performed at one time by processing a hot press jig to a predetermined size.

Furthermore, by applying a liquid such as silicone oil to the inner wall of the unwelded part 4 as shown in Figure 3a, the unwelded part 4 will close tightly when the pressure is reduced due to the surface tension of the liquid, and air will be drawn into the battery. Alternatively, as shown in Figure 3b, you can apply a liquid 9 such as silicone oil to the inner wall of the unwelded part 4, and then cover the unwelded part with an elastic material from the outside of the battery case. Reliability can be further improved by applying external force by holding the battery with clips 10 (thickness: 1.0 mm) so that the valve does not open unless the pressure inside the battery becomes high.

Next, the self-discharge characteristics of the battery with the above configuration were investigated. FIG. 4 is a characteristic diagram showing the relationship between the standing period and the remaining capacity (ratio when the initial performance is 100%) when each of the above batteries is left in an atmosphere of 40° C. after being fully charged. A is a conventional example, B is a first embodiment of the present invention (shown in FIG. 2), and B has slightly inferior self-discharge characteristics compared to A.

There is also a battery C of the second embodiment of the present invention (the one in FIG. 3a) which has the same structure as B but has a liquid 9 such as silicone oil applied to the inner wall of the unwelded part, and a battery C (the one in FIG. 3a) in which a liquid 9 such as silicone oil is applied. A battery D according to a third embodiment of the present invention (the one shown in FIG. 3b) is coated on the inner wall of the unwelded part 4, and the unwelded part is held from the outside with clips 10 made of an elastic material such as ABS. It was possible to obtain almost the same characteristics as the conventional battery A.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained, and a sealed battery suitable as a power source for inexpensive and small-sized portable electrical equipment can be provided.

(1) Due to its structure, in which a heat-welded sheet or film-like synthetic resin body is left unwelded to function as a safety valve, it is not only extremely easy to mechanize, but also can be formed in a short time, making it superior to conventional products. In comparison, it requires fewer man-hours, has high productivity, and can reduce manufacturing costs.

(2) The battery case with a safety valve function is integrally formed by wrapping the electrode plate group in a sheet-like or film-like synthetic resin body, so it is difficult to attach the electrode plate to the case with conventionally structured batteries. It becomes easy to mechanize the insertion of groups, and the number of man-hours can be reduced.

(3) In terms of materials, the battery case with the safety valve function can be constructed from only a thin sheet-like or film-like synthetic resin body, which reduces material costs.

[Brief explanation of drawings]

Figure 1 is a perspective view of a conventional sealed lead-acid battery;
The figure is a perspective view of a sealed lead-acid battery according to an embodiment of the present invention, FIGS. 3a and 3b are enlarged views of main parts showing another embodiment, and FIG. 4 is a diagram showing self-discharge characteristics. 4...Unwelded part, 5...Welded part, 6... Plate group, 7... Pole column, 8... Battery case.

Claims (1)

[Scope of Claims] 1. An electrode plate group 6 consisting of a positive electrode plate, a negative electrode plate, and a separator separating the above-mentioned both electrode plates, an electrolytic solution held in the electrode plate group, and an electrolyte-resistant and heat-weldable electrode group 6. A battery case 8 made of a synthetic resin film or sheet;
Consisting of a pair of pole posts 7 connected to the electrode plate group,
The battery case has a sealing part provided in a part surrounding the electrode plate group, the pole pillar extends outward through the sealing part, and the sealing part connects the resin films or sheets to each other. It has a thermally welded part 5 and an unwelded part 4, the inside of the cell and the outside communicate with each other through the unwelded part, and the unwelded part has a close contact part where the resin films or sheets overlap each other, and the inside of the cell is connected to the outside. A sealed lead-acid battery configured so that when the cell becomes overpressured, the gas inside the cell can push out the tight contact area and escape to the outside, thereby functioning as a safety valve. 2. The sealed lead-acid battery according to claim 1, wherein the unwelded synthetic resin films or sheets overlap each other in a maze-like shape. 3. The sealed lead-acid battery according to claim 1 or 2, wherein silicone oil is applied to the unwelded portion of the close contact portion. 4. The sealed lead-acid battery according to any one of claims 1 to 3, wherein the outside of the unwelded part of the sealing part is held with a clip.