JPH0471310B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement in the safety valve portion of a sealed lead-acid battery.

Conventional examples, configurations, and their problems Sealed lead-acid batteries have a separator made of glass fiber that retains the electrolyte and prevents it from flowing.
Since the electrolyte does not leak outside, it is widely used as a compact, portable power source. Recently, with the aim of reducing the cost of batteries, various proposals have been made to change the battery container from a monoblock resin case to a bag-like exterior body made of film-like or sheet-like synthetic resin. This sealed battery generally has 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, the internal battery pressure In the worst case, there is a risk of damage. Furthermore, if the battery is left unattended, the oxygen gas generated during charging inside the battery will be absorbed by the negative electrode.
In addition, hydrogen gas passes through the synthetic resin and is released into the air, creating a reduced pressure state. If there are holes in the synthetic resin, the negative electrode plate will be oxidized by oxygen gas in the air and deteriorate. For this reason, safety valves with non-return properties are provided, and various proposals have been made regarding bag-like exterior bodies for this purpose. FIG. 1 shows an example of this, in which a flat electrode group 4 consisting of a positive electrode plate 1, a negative electrode plate 2, and a separator 3 is bonded to two film-like or sheet-like synthetic resin bodies 5 that are acid-resistant and heat-weldable. The synthetic resin body around the electrode plate group 4 is thermally welded with some unwelded parts left in order to conduct electricity.
It was made to protrude upwards and bent into a V-shape to serve as a safety valve. 7 is a pole for extracting electricity.
However, with such a structure, it is difficult to uniformly adhere the two sheets of synthetic resin. In other words, if the dimensions of the two synthetic resin sheets differ even slightly, a gap may occur, and even if they are in close contact, the exterior body is made of synthetic resin film and is easily deformed by external pressure, pushing the pole column toward the valve. Even if the power is only concentrated on the safety valve, the safety valve changes and a gap is created, allowing electricity to enter the electrical equipment and degrade its performance. Also V
The valve pressure tends to change depending on the size of the radius of curvature R when bent into a letter shape, and the protruding length of the tongue piece is long, so the amount of gas released from the inside is small, and when charging with a large current. There was a risk that the gas could not be released completely and the exterior body would be destroyed. Further, due to the length, there were problems such as high material costs and an increase in the apparent size of the battery.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
The purpose of this invention is to improve the reliability of the safety valve part of a sealed storage battery using a film or sheet type battery, reduce costs, and downsize the battery.

Structure of the Invention The present invention comprises sandwiching an electrode plate group consisting of a positive electrode plate, a negative electrode plate, and a separator between film-like or sheet-like synthetic resin bodies that are acid-resistant and heat-weldable.
The synthetic resin body around the electrode plate group leaves some unwelded parts and is thermally welded to generate electricity, and the unwelded parts are opened when the internal pressure of the battery is higher than the external pressure, and conversely when it is lower. In a sealed lead-acid battery, a safety valve is formed by making two film-like or sheet-like synthetic resin bodies in close contact with each other without a gap so that the gap is sealed, and the safety valve part is made to protrude upward. , one point is bent in a V-shape across the protrusion, for example at the base of the safety valve part, and then returned to its original position to form a crease. With this configuration, a highly reliable battery can be miniaturized and material costs can be reduced, and the battery can be provided at low cost.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on the drawings. In FIG. 2, a flat electrode group 4 consisting of one positive electrode plate 1, two negative electrode plates 2, and a separator 3 made of glass mat is connected to a 0.1 mm thick electrode plate group 4 that is acid-resistant and heat-weldable. Sandwiched between two sheets of film-like or sheet-like polyethylene 5, only the bottom and left and right sides of the periphery of the electrode plate group 4 are heated from the outside at 130 ° C. for 10 seconds using a heat press,
Attempts are made to weld 9 polyethylene to each other and conduct electricity.
Next, an electrolytic solution consisting of a predetermined dilute sulfuric acid is injected from the unwelded upper part. After injecting the liquid, the upper part is heat-pressed again under the same conditions as above to seal the pole pillar 7, and at the same time, the inner surfaces of the two film-like or sheet-like polyethylene 5 face parallel to each other without any gaps and are closely attached. The unwelded part was formed as a safety valve 6 in the center. This unwelded part opens when the internal pressure of the battery is higher than the external pressure (when pressurized) and releases the gas generated from the electrode plate group through the gap, and conversely closes when it is low (when pressure is reduced). It acts like a safety valve to seal the gap. To explain this safety valve portion 6 in more detail, the unwelded portion is formed into an elongated tongue shape as shown in FIG. 2, and is made to protrude upward. After welding the left and right ends as described above, bend the base of the safety valve 6 into a V shape by 180° and return it to its original position. However, in reality, a portion of the polyethylene film or sheet itself undergoes material failure, and it does not return to its original shape completely, but instead becomes bent at an approximately doglegged bending angle of about 5 to 10 degrees.
In this state, the two polyethylene sheets are fixed with the same length at the fold 8 as shown in Figure 3, and then the inside 1
0 is a state in which the outer side 11 has not been fully shrunk and is pushing the inner side 10, and the outer side 11 has not been fully expanded and is pushing the inner side 10, that is, the two polyethylene sheets are in close contact with each other. Specifically, when the valve opens, both the inner side 10 and the outer side 11 are pushed by gas pressure from inside, so the bending angle increases.
In other words, it points in the direction where the interior angle becomes larger. Conversely, when the pressure inside the battery decreases, the polyethylene returns to its original state due to its own force, and the two polyethylene sheets come into close contact (closed) as shown in Figure 3. In this way, by using thin and easily deformable polyethylene, we ensure that the two polyethylene sheets stick together by creating creases, and by providing a bending angle, it does not deform in response to forces from the direction of the pole. In addition to making it difficult,
When the valve opens, the valve pressure does not increase due to the extension of the dogleg-shaped bending angle. In addition, the amount of ventilation is ensured by shortening the length of the valve. Moreover, in order to further improve the adhesion between these two polyethylene sheets, it is preferable to apply silicone oil.

It was found that the valve does not open when the dogleg-shaped bending angle is 90°, and that a shallow bending angle of 5 to 10° is sufficiently effective.

Further, the valve opening pressure changes depending on the ratio of the welded width to the unwelded width. In general, it was found that a ratio of 1:1 is desirable, and the larger the weld width, the lower the valve opening pressure. It was also found that, regardless of the length of the unwelded portion, if there is a crease, the valve pressure becomes constant at the bending angle. In other words, the length of the unwelded portion can be shortened and the valve can be made smaller.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) Even if there is a gap in the safety valve, the polyethylene at the crease will stick together by bending it.

(2) By bending the safety valve part into a dogleg shape, the physical strength is improved and the safety valve part is less likely to deform even if the pole pillar deforms inward.

(3) Since the safety valve can be made smaller, the battery can be made smaller.

(4) It is possible to reduce the amount of film-like or sheet-like synthetic resin material, and it is possible to reduce the cost of materials.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a sealed lead-acid battery using a conventional bag-like exterior body, Fig. 2 is a perspective view of a sealed lead-acid battery according to an embodiment of the present invention, and Fig. 3 is a sectional view of the essential parts. It is. DESCRIPTION OF SYMBOLS 1... Positive electrode plate, 2... Negative electrode plate, 3... Separator, 4... Electrode plate group, 5... Film-like or sheet-like synthetic resin body, 6... Safety valve, 8... Crease,
9, 9'...Welded part.

Claims (1)

[Scope of Claims] 1. An electrode plate group consisting of a positive electrode plate, a negative electrode plate, and a separator is sandwiched between acid-resistant and heat-weldable film-like or sheet-like synthetic resin bodies, and the surrounding area of the electrode plate group is synthesized. The resin body is a sealed type with a safety valve in which the inner surfaces of the two synthetic resin sheets are tightly adhered to each other without any gaps. In a lead-acid battery, the safety valve has a shape that protrudes upward from the heat welded part around the electrode plate group, and both sides of this protrusion are heat welded, and the unwelded part extends from the electrode plate group to the tip of the protrusion. V to cross this protrusion.
A sealed lead-acid battery characterized in that it is bent into a letter shape to form a crease, and the protrusion after the bending is formed into a substantially dogleg shape. 2. The sealed lead-acid battery according to claim 1, wherein the bent angle of the substantially doglegged shape is 5 to 10 degrees.