JP2001023595A - Explosion protecting safety valve for sealed battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an explosion protecting safety valve for a sealed battery, equipped with a structure providing a fixed release pressure as a safety valve while securing a remaining thickness not causing a failure of airtightness, in the case of a coined safety valve. SOLUTION: In a coined safety valve, an easily deformable groove 4 forming an easily movable part as provision for an increased internal pressure is formed around an outline forming groove 2 formed by a marking punch 3. Lateral stresses are applied to the outline forming groove 2 formed by the marking punch 3 by applying lateral stresses on a bottom part of the outline forming groove 2 formed by the marking punch 3. This enables a fixed working pressure as a safety valve to be obtained while securing a remaining thickness not causing a failure of airtightness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an explosion-proof safety valve which releases internal pressure to the outside when the internal pressure rises in a sealed battery, particularly a battery having a high energy density such as a lithium secondary battery, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A sealed battery having a high energy density, such as a lithium secondary battery, generates a chemical reaction inside the battery due to an overcharge due to a failure of a related device including a charger or an external short circuit due to an erroneous use. Accompanying this, abnormal gas may be generated. At that time, the internal pressure of the battery abnormally increases, which may adversely affect devices driven by the battery and objects around the device.

Therefore, in order to prevent such an adverse effect on a sealed battery having a high energy density, a part of a sealing plate or a part of a sealed metal container is generally provided with a circle, an oval, a polygon, or the like. A contour forming groove is formed by using a stamping punch in the contour shape of this, and when the internal pressure of the battery rises abnormally, the part of the contour forming groove breaks to form an opening, and a gas-filled safety valve that discharges gas from here. Is provided.

FIG. 4 shows a sealing device provided with an engraved safety valve.

[0005] In FIG. 4, reference numeral 41 denotes a sealing device, which is provided at an upper opening of a battery case containing a positive electrode plate, a negative electrode plate, a separator interposed between the positive electrode plate and the negative electrode plate, and an electrolyte. The battery case is sealed and mounted. The sealing device 41 has an upper metal plate 44 sandwiched between an outer sealing plate 42 and an inner sealing plate 43.
4, a contour forming groove 45 is formed by a stamping punch as shown in FIG. When the internal pressure of the battery case rises abnormally, the contour forming groove 45 is broken and the opening 46 of the inner sealing plate 43 and the opening 47 of the outer sealing plate 42 communicate with each other, so that gas in the battery passes through the communication passage. This prevents the battery from swelling and exploding by being released outside the battery.

The release pressure at which the contour forming groove 45 is broken is the contour of the contour forming groove 45 formed by the engraving punch 48, as shown in FIG. It is determined by the width of the small area portion 49 of the shape and the remaining thickness 50 of the contour forming groove 45 formed by the stamping punch as shown in FIG. In order to obtain an appropriate release pressure, it is necessary to either increase the small area portion 49 of the contour shape by the marking punch 48 or reduce the remaining thickness 50 of the contour forming groove 45 by the marking. However, it is difficult to enlarge the small area portion 49 of the contour shape by the marking punch 48 in a limited size like a small sealed battery. Therefore, an appropriate release pressure is obtained by reducing the remaining thickness 50 of the contour forming groove 45 by engraving.

[0007]

In the above-mentioned conventional engraving type safety valve, the contour forming groove 4 formed by the engraving punch 48 is particularly used.
In the case where the inside and outside of the portion constituting the portion 5 have a small amount of deformation with respect to a change in pressure, the remaining thickness 50 of the engraved portion must be reduced to about 10 microns in order to obtain a predetermined release pressure. .

However, in the conventional engraving type safety valve, in order to form the contour forming groove 45, a wedge-shaped engraving punch having a V-shaped cross section or a minute flat portion is used as a part of the sealing plate. Alternatively, a small crack is generated in the direction in which the marking punch is driven because the metal punch is processed by being driven into a part of the metal container. At this time, the depth of the crack generated in front of the marking punch may be several microns to several tens of microns. Further, when the material of the sealing plate or the metal container forming the contour forming groove by the stamping punch is, for example, an aluminum alloy, a pinhole of about 10 μm may be present depending on the added metal for alloying.
As described above, when the bottom thickness of the contour forming groove formed by the stamping punch is reduced to about 10 μm, the possibility that cracks or pinholes exist at the bottom of the contour forming groove increases, which results in poor airtightness. Such a problem arises.

Accordingly, the present invention provides an explosion-proof safety valve for a sealed battery having a configuration for obtaining a predetermined release pressure of a safety valve while securing the remaining thickness at the bottom of the contour forming groove where no poor airtightness occurs. The purpose is to:

[0010]

In order to achieve the above object, an explosion-proof safety valve for a sealed battery according to the first aspect of the present invention is provided with a contour forming groove provided in a part of a sealing plate or a metal container. Form an easily deformable groove in close proximity, and apply a horizontal stress to the contour forming groove by the flow and deformation of the excess wall pushed away by the stamping punch at the time of forming the easily deformable groove,
A thin portion is formed between the contour forming groove and the easily deformable groove with a residual stress. Accordingly, even if the remaining thickness of the bottom of the contour forming groove of the conventional engraved safety valve is the same, a lower operating pressure of the safety valve can be obtained due to the presence of the easily deformable groove and the existence of the residual stress when the internal pressure of the battery rises.

According to the second aspect of the present invention having the same object, a small area surrounded by the contour forming groove is displaced stepwise from the outer peripheral surface of the contour forming groove to form a thin portion. Due to the presence and the residual stress, the operating pressure of the safety valve can be obtained without reducing the remaining thickness at the bottom of the contour forming groove.

According to the third aspect of the present invention having the same object, the safety valve is deformed flat when the contour forming groove is formed, so that the residual stress from the periphery of the contour forming groove is present to ensure safety. A valve that is easy to operate can be manufactured.

[0013] According to the above inventions, the bottom thickness of the contour forming groove which is not affected by the cracks at the time of forming the contour forming groove by the stamping punch and the pinhole derived from the material constituting the contour forming groove is ensured. An explosion-proof safety valve of a sealed battery having a predetermined valve operating pressure is obtained.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention described in the claims of the present invention
After forming a contour forming groove of a stamping type safety valve provided on a part of the sealing plate or a metal container by a stamping punch, an easily deformable groove is formed near the contour forming groove, and a stamping punch forming the easily deformable groove is formed. Applying lateral stress to the bottom of the contour forming groove that forms the engraved safety valve due to the flow or deformation of the surplus wall that is displaced, the residual stress exists, or the inner peripheral part of the contour forming groove is stepped upward Alternatively, a thin portion can be easily formed by protruding downward.

Further, the sealing plate or the metal container deformed by the configuration of the contour forming groove is flattened by pressing with a flat press, so that stress is applied to the contour forming groove from the periphery.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited only to the embodiments described below.

(Embodiment 1) FIG. 4 shows a cross section of an explosion-proof sealing device for a sealed battery in which an explosion-proof safety valve for a sealed battery is incorporated as in the prior art. As shown in FIG. 1, the upper metal plate 1 according to the first embodiment for forming the safety valve has a thickness of 0.06 mm, a length of 27.3 mm, and a width of 3.
Made of 5mm aluminum, φ1.8mm, depth 0.0
A contour forming groove 2 with a 4 mm mark is provided. The contour forming groove 2 forms a contour such as a circle, an ellipse, or a square which breaks when the internal pressure of the battery becomes abnormally high and releases the internal pressure of the battery. FIG. 1 shows a step of pressing the upper metal plate 1. After the contour forming groove 2 is formed by the marking punch 3, an easily deformable groove 4 serving as an easily deformable portion is further formed on the outer periphery of the contour forming groove 2 by the marking punch 3 as shown in FIG. It is formed on the inner periphery of the contour forming groove 2 as shown in FIG. At this time, due to the flow and deformation of the material due to the formation of the easily deformable groove 4,
A stress is applied to the bottom of the contour forming groove 2 from the lateral direction as indicated by an arrow, thereby giving a residual stress.

Therefore, even when the remaining thickness of the contour forming groove 2 is large, the thin portion 5 is formed by forming the easily deformable groove 4, and the portion surrounded by the contour forming groove 2 is easily broken in response to the rise in the internal pressure of the battery. . Note that an easily deformable groove 4 that opens in a direction opposite to the contour forming groove 2 may be formed on the inner periphery and the outer periphery of the contour forming groove 2. The thickness of the thin portion 5 is preferably smaller than the thickness of the bottom of the contour forming groove 2.

(Embodiment 2) FIG. 2 shows a plan view of an upper metal plate 6 forming an explosion-proof safety valve for a sealed type battery according to Embodiment 2 and a cross section of a main part thereof. The metal plate 6 has a thickness of 0.06 mm and a length of 27.3.
mm, 3.5mm wide aluminum, φ1.8m
The contour forming groove 7 is provided in the same manner as in the first embodiment by engraving of m and a depth of 0.04 mm. Next, FIG. 2 shows a step of pressing the upper metal plate 6. FIG. 2B shows a cross section of the contour forming groove 7 formed by the marking punch 8.
As shown in FIG. 2B, the periphery of the contour forming groove 7 formed by the marking punch 8 is deformed due to the flow of the material as shown by the arrow in FIG. 2B. Next, the inner peripheral portion 9 of the contour forming groove 7 is formed into a convex shape from the side opposite to the opening of the contour forming groove 7 by presses 10a and 10b. As a result, as shown in FIG. 2D, the projecting step 11 is formed, and a lateral stress is applied to the contour forming groove 7 as indicated by an arrow, thereby giving a residual stress.

Therefore, even if the remaining thickness of the bottom of the contour forming groove 7 is large, the upper metal plate 6 is easily broken by the contour forming groove 7.

(Embodiment 3) FIG. 3 shows an upper metal plate 12 forming an explosion-proof safety valve of a sealed battery according to Embodiment 3.
2 shows a cross section of a main part of the safety valve. The upper metal plate 12 forming the safety valve has a thickness of 0.06 mm and a length of 2 mm.
It is made of aluminum with a width of 7.3 mm and a width of 3.5 mm.
The contour forming groove 13 is stamped with a mark of 8 mm and a depth of 0.04 mm.
Is provided. Next, FIG. 3 shows a step of pressing the upper metal plate 12. FIG. 3B shows a cross section after the contour forming groove 13 is formed by the marking punch 14. This figure 3
As shown in (b), the periphery of the contour forming groove 13 formed by the marking punch 14 is deformed as indicated by an arrow due to the flow of material or the like. Next, the periphery of the contour forming groove 13 is sandwiched between the flat surfaces 15a and 15b to correct the deformed portion 16 and, as shown in FIG. 3D, an arrow is provided at the bottom of the contour forming groove 13 formed by the stamping punch. As described above, a stress is applied in the lateral direction to give a residual stress.

Therefore, the contour forming groove 13 is easily broken due to an increase in the internal pressure of the battery.

Table 1 shows the operating pressure of the explosion-proof safety valve of the sealed battery and the operating pressure of the safety valve according to the conventional engraving method obtained by the above-mentioned means. From Table 1, by using the explosion-proof safety valve of the sealed battery having the configuration according to the first, second, and third embodiments, it is possible to obtain a predetermined operating pressure of the safety valve while securing a remaining thickness that does not cause airtight failure. Understand.

[0024]

[Table 1]

[0025]

As described above, according to the present invention, an easily deformable groove is formed around the contour forming groove formed by the stamping punch, thereby forming a thin portion which becomes an easily movable portion when the internal pressure rises. At the same time, applying a stress from the lateral direction to the bottom of the contour forming groove by the stamping punch, or providing a protruding step inside the contour forming groove to form a thin portion or deforming when forming the contour forming groove. By applying a stress from the lateral direction of the contour forming groove by the stamping by pressing, while securing the remaining thickness that does not cause airtight failure,
An explosion-proof safety valve of a sealed battery having a configuration for obtaining a predetermined operating pressure of the safety valve is obtained.

[Brief description of the drawings]

FIG. 1 is a plan view and a cross-sectional view of a principal part of an explosion-proof safety valve of a sealed battery according to a first embodiment.

FIG. 2 is a sectional view of an essential part of an explosion-proof safety valve of a sealed battery according to Embodiment 2.

FIG. 3 is a sectional view of an essential part of an explosion-proof safety valve of a sealed battery according to a third embodiment;

FIG. 4 is a cross-sectional view of a sealing device for a sealed battery provided with an engraved safety valve and an explanatory view of a main part.

[Explanation of symbols]

 1, 6, 12 Upper metal plate 2, 7, 13 Contour forming groove 3, 8, 14 Marking punch 4 Easily deformable groove 5 Thin portion 9 Inner peripheral portion 10a, 10b Press 11 Protrusion 15a, 15b Flat surface 16 Deformation portion

Claims (3)

[Claims] A positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte are hermetically housed in a metal battery case, and a part or a part of a sealing plate for sealing the metal battery case. An explosion-proof safety valve comprising a contoured groove that forms a small area portion that functions to release the internal pressure of the battery to the outside of the battery when the internal pressure of the battery abnormally rises in a part of the metal battery case, Forming an easily deformable groove that opens in the opposite direction to the opening direction of the contour forming groove in the vicinity of the inner circumference or the outer circumference or both the inner circumference and the outer circumference of the contour forming groove, and easily deforms with a side portion of the contour forming groove; An explosion-proof safety valve for a sealed battery, wherein a thin portion is formed by a side portion of the groove. 2. A positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte hermetically housed in a metal battery case, and part or a part of a sealing plate for sealing the metal battery case. An explosion-proof safety valve comprising a contoured groove that forms a small area portion that functions to release the internal pressure of the battery to the outside of the battery when the internal pressure of the battery abnormally rises in a part of the metal battery case, The small area portion surrounded by the contour forming groove is formed by being recessed stepwise from the outer peripheral surface of the contour forming groove or formed so as to protrude stepwise, and the side portion of the contour forming groove and the small area are formed. An explosion-proof safety valve for a sealed battery, wherein a thin portion is formed between the explosion-proof part and the part. 3. A positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte hermetically housed in a metal battery case, and part or a part of a sealing plate for sealing the metal battery case. A method of forming a contour forming groove that forms a small area portion that functions to release the internal pressure of the battery to the outside of the battery by being broken by the internal pressure when the internal pressure of the battery abnormally increases in a part of the metal battery case, The contour forming groove is formed by a stamping punch on a part of the sealing plate or the metal battery case, and a part of the sealing plate or the metal is formed close to the contour forming groove by pressing the stamping punch. An explosion-proof safety valve for a sealed battery, wherein a deformed portion formed in a part of the battery case is flattened by pressing with a flat press, and stress is applied to the contour forming groove from the periphery. Manufacturing of Method.