JP7570093B2 - Battery cover - Google Patents

Description

This invention relates to a battery cover made of metal plate that is used to seal a battery case.

Conventionally, lithium ion batteries, nickel-metal hydride batteries, and the like have used sealed battery cases that house their power generating elements, with a battery lid attached to the opening of a bottomed cylindrical case body.

A commonly used battery cover is one made of a metal plate that has a valve that breaks open when a certain pressure is applied and a surrounding plate portion connected to the valve, which is molded as one unit. The valve has a thin-walled portion that is thinner than the surrounding plate portion, and when the battery's internal pressure reaches a certain pressure, it begins to break open from the thin-walled portion. The valve functions as a safety valve to prevent the battery case from exploding if the battery's internal pressure increases abnormally. This type of battery cover is generally mass-produced by pressing using a progressive die. During manufacturing, the dimensions of the thin-walled portion are controlled so that the valve breaks open at the specified pressure.

There is a concern that foreign matter such as electrolyte, water, and oil may adhere to the battery lid as described above. If such foreign matter adheres to the thin wall of the valve, it will cause corrosion, and the pressure at which it ruptures (rupture pressure) will change from the specified pressure. To prevent this, the valve is covered with a film or seal adhered to a metal plate, or a protective resin is applied to the valve (Patent Documents 1 to 3).

Patent No. 6252877 Patent No. 4100762 Patent No. 5407683

However, when a film or the like is attached separately to protect the valve so that foreign matter does not adhere to the valve and the rupture pressure does not change from the specified pressure, as in Patent Documents 1 to 3, there is a problem that the cost of procuring the parts and carrying out the attachment process is high. In addition, there may be cases where the film or the like prevents the valve from rupturing smoothly.

In view of the above background, the problem that this invention aims to solve is to protect the valve without attaching a separate valve protection member to the battery lid, and without preventing the valve from opening.

In order to achieve the above object, the present invention provides a battery lid made of a metal plate in which a valve that breaks open when a predetermined pressure is applied and a surrounding plate portion connected to the valve are integrally formed, the valve comprises a pressure receiving portion that protrudes to one side, and a thin portion that is thinner than both the pressure receiving portion and the surrounding plate portion and connects the pressure receiving portion to the surrounding plate portion, and the pressure receiving portion has a protective cover that extends into the air to cover the thin portion from one side.

According to the above configuration, the pressure-receiving portion protruding to one side can be made thicker than the thin-walled portion, making it possible to make it a portion where there is no concern of the rupture pressure being affected even if foreign matter adheres to the pressure-receiving portion. Furthermore, when pressing the valve, the thickness of the protruding portion that serves as the pressure-receiving portion can be utilized to mold a protective cover that extends into the air toward the thin-walled portion as one piece with the pressure-receiving portion. By having this protective cover that extends into the air cover cover the thin-walled portion from one side, the protective cover prevents foreign matter from adhering to the thin-walled portion that determines the rupture pressure of the valve, and also ensures a gap so that the protective cover does not come into contact with other parts of the metal plate and impede the rupture of the valve.

Therefore, by adopting the above configuration, the battery cover of this invention can protect the valve without attaching a separate valve protection member to the battery cover, and without preventing the valve from opening.

An enlarged cross-sectional view of a battery cover according to a first embodiment of the present invention taken along line II in FIG. FIG. 2 is a plan view showing the battery cover of FIG. An enlarged view of the valve of FIG. Enlarged view of the protective cover in Figure 1 FIG. 2 is a cross-sectional view showing a half-punching process for forming the pressure-receiving portion of FIG. FIG. 6 is a cross-sectional view showing a pressing process subsequent to FIG. 5 . FIG. 7 is a cross-sectional view showing the stamping of the rupture groove, following FIG. FIG. 8 is a cross-sectional view showing a curling process for forming a protective cover, following FIG. 7 . FIG. 9 is a cross-sectional view showing a protective cover formed by the curling process of FIG. 8. FIG. 11 is a cross-sectional view showing a main part of a battery cover according to a second embodiment of the present invention.

Below, a first embodiment of a battery cover according to the present invention will be described with reference to the attached drawings.

The battery lid shown in Figures 1 and 2 is made of a metal plate in which a valve 1 that breaks open when a certain pressure is applied and a surrounding plate portion 2 that is connected to the valve 1 are integrally formed. This battery lid is an example of a battery lid for a rectangular battery. The periphery of the battery lid is joined to the nozzle portion (not shown) of the cylindrical case body with a bottom.

The metal plate is generally a material that can be pulled out of an uncoiler and pressed using a progressive die, a typical example being an aluminum alloy plate.

The valve 1 consists of a pressure-receiving portion 3 that protrudes to one side, and a thin-walled portion 4 that is thinner than the pressure-receiving portion 3 and connects the pressure-receiving portion 3 to the surrounding plate portion 2. Here, "one side" refers to the direction going in one direction in the thickness direction, and the direction going in the opposite direction to the one side is called the "other side." In Figure 1, the thickness direction corresponds to the up-down direction, with the one side corresponding to the upper side and the other side corresponding to the lower side.

The surrounding plate portion 2 surrounds the valve 1, is thicker than the thin-walled portion 4, and continues around the thin-walled portion 4. The thickness of the surrounding plate portion 2 is the thickness of the portion adjacent to the valve 1, and is set to be substantially equal to the thickness of the metal plate used as the material.

The pressure-receiving portion 3 protrudes high from the thin-walled portion 4 to one side. The base portion of the pressure-receiving portion 3 is a solid cylinder that is thicker than the thin-walled portion 4. The thin-walled portion 4 extends in an annular shape that surrounds the base portion of the pressure-receiving portion 3.

The plate surface on the other side of the pressure-receiving portion 3 and the thin-walled portion 4 forms a concave bottom surface portion with a depth on one side from the plate surface on the other side of the surrounding plate portion 2, and is molded into a flat surface. Here, a flat surface refers to a surface shape that extends in a direction perpendicular to the thickness direction.

The pressure-receiving part 3 has a protective cover 5 that extends into the air so as to cover the thin-walled part 4 from one side. The protective cover 5 protrudes higher in a cylindrical shape from the base part of the pressure-receiving part 3 to one side, and the tip of the cylindrical cover is curled toward the thin-walled part 4.

As shown in Figures 3 and 4, the thin-walled portion 4 has a rupture groove 6 that is engraved with a groove depth in the thickness direction and passes through the area between the pressure-receiving portion 3 and the surrounding plate portion 2. The rupture groove 6 is engraved on one side of the thin-walled portion 4. The rupture groove 6 extends in a circular ring shape concentric with the circumferential shape of the outer periphery of the pressure-receiving portion 3. The groove cross-sectional shape of the rupture groove 6 is V-shaped.

Of the thin-walled portion 4, the plate surface between the rupture groove 6 and the pressure-receiving portion 3, and the plate surface between the rupture groove 6 and the surrounding plate portion 2, are each molded to have a flat surface. The plate surface between the rupture groove 6 and the surrounding plate portion 2 and the plate surface on one side of the plate portion 2 are flush with each other. The pressure-receiving portion 3 also has a protruding height on one side relative to the surrounding plate portion 2.

The tip 7 of the protective cover 5 faces the surrounding plate portion 2 with a gap. This facing gap is set to the smallest gap formed by the protective cover 5 with the thin-walled portion 4 and the surrounding plate portion 2.

The battery lid shown in Figures 1 and 2 is joined to the nozzle (not shown) of the case body with one side of the battery lid facing the outside of the battery. Even if foreign matter (not shown) such as electrolyte, water, oil, etc. gets on one side (exterior side) of the battery lid, the thin-walled portion 4 is covered from one side with the protective cover 5, so the protective cover 5 prevents the foreign matter from adhering to the thin-walled portion 4.

When the internal pressure of the battery (not shown) rises, pressure (internal battery pressure) acts on the valve 1 from the other side (inside the battery) to one side (outside), and the pressure-receiving portion 3 and the thin-walled portion 4 are pushed to one side relative to the surrounding plate portion 2, causing the valve 1 to expand. At this time, since the thickness of the thin-walled portion 4 is sufficiently thin compared to the thicknesses of the pressure-receiving portion 3 and the surrounding plate portion 2, the thin-walled portion 4 is pulled to one side by the internal battery pressure, as shown by the dashed line in FIG. 4. This tensile stress changes depending on the magnitude of the internal battery pressure acting on the valve 1. When the pressure acting on the valve 1 reaches a certain pressure, the valve 1 ruptures, especially at the bottom of the thin rupture groove 6, as it cannot withstand the tensile stress, and the valve 1 is ruptured starting from this point. Then, as the rupture progresses rapidly along the bottom of the rupture groove 6, the opening area of the valve 1 rapidly expands. At this time, the protective cover 5 is part of the pressure-receiving part 3 that is located in the hollow on one side relative to the thin-walled part 4 and the surrounding plate part 2, so it can be easily detached from the battery lid together with other parts of the pressure-receiving part 3 and the rupture fragment part of the thin-walled part 4 on the pressure-receiving part 3 side, and there is no concern that it will prevent the valve 1 from opening.

The gap between the tip 7 of the protective cover 5 and the surrounding plate 2 is the only path through which foreign matter can enter, so it should be as narrow as possible. Taking into consideration the feasibility of press working, prevention of foreign matter from entering, and the assurance of the rupture pressure of the valve 1, the size of the gap is preferably 0.5 mm or more and 2.0 mm or less.

The method of pressing the above-mentioned valve 1 using a progressive die is illustrated in Figs. 5 to 9. Note that the upper side in these figures corresponds to one side of the above-mentioned battery lid.

First, as shown in FIG. 5, the workpiece W, a strip of metal plate, is fed between the lower punch P1 and the upper dies D1, D2, and the punch P1 and the dies D1, D2 form the workpiece W so that it is convex on the top and concave on the bottom, protruding the solid columnar portion 11 and thinning the periphery of the solid columnar portion 11.

The workpiece W is sent between the lower die D3 and the upper punch P2 and die D4 shown in Figure 6, and part of the solid columnar portion 11 is recessed downward, causing the plastically flowing flesh to protrude further upward into a cylindrical shape. This forms a solid cylindrical base portion 12 and a cylindrical portion 13 that is concentric with the base portion 12 and protrudes further upward.

The workpiece W is then fed between the lower die D5 and the upper punch P3 shown in FIG. 7, and the stamping punch P3 of the upper die is used to stamp the rupture groove 6 into the thin-walled portion around the base portion 12. This completes the formation of the thin-walled portion 4.

The workpiece W is sent between the lower die D6 and the upper punch P4 shown in FIG. 8, and the cylindrical portion 13 is curled. The cylindrical portion 13 is slid from the tip onto the face of the punch P4 and curled toward the thin-walled portion 4, completing the formation of the pressure-receiving portion 3 including the protective cover 5, as shown in FIG. 9.

In the next process, the workpiece W is trimmed to form the periphery of the battery lid as shown in Figure 1.

The thickness of the metal plate (corresponding to the thickness of the surrounding plate portion 2) is preferably 2.0 mm or more, more preferably greater than 3.0 mm and 5.0 mm or less. If the thickness of the metal plate is 2.0 mm or more, it is possible to ensure the volume of the flesh for forming the pressure-receiving portion 3 including the protective cover 5, and if it is 5.0 mm or less, it is possible to accommodate press processing using a progressive die.

As described above, the battery lid shown in Figures 1 to 4 is made of a metal plate in which the valve 1 and the surrounding plate portion 2 are molded as a single unit, and the valve 1 is made of a pressure-receiving portion 3 that protrudes to one side and a thin-walled portion 4 that is thinner than both the pressure-receiving portion 3 and the surrounding plate portion 2 and connects the pressure-receiving portion 3 to the surrounding plate portion 2. The pressure-receiving portion 3 has a protective cover 5 that extends into the air to cover the thin-walled portion 4 from one side, making the pressure-receiving portion 3 that protrudes to one side thicker than the thin-walled portion 4 and making it a portion that will not affect the rupture pressure even if foreign matter adheres to the pressure-receiving portion 3. Furthermore, when the valve 1 is pressed (see Figures 5 to 9 as appropriate), the thickness of the protruding portion (solid columnar portion 11) that constitutes the pressure-receiving portion 3 can be used to mold the protective cover 5 that extends into the air toward the thin-walled portion 4 as a single unit with the pressure-receiving portion 3. The protective cover 5 extends into the hollow and covers the thin-walled portion 4 from one side, preventing the adhesion of foreign matter to the thin-walled portion 4, which determines the rupture pressure of the valve 1, and also ensures a gap so that the protective cover 5 does not come into contact with other parts of the metal plate and prevent the rupture of the valve 1. By protecting the thin-walled portion 4 with the protective cover 5 molded as part of the pressure-receiving portion 3 of the valve 1 in this way, there is no need to protect the valve 1 from the adhesion of foreign matter with a separate protective member. Therefore, the battery lid shown in Figures 1 to 4 can protect the valve 1 without attaching a separate member for protecting the valve 1 to the battery lid, and without preventing the valve 1 from rupturing.

The protective cover 5 is formed by protruding a solid columnar portion 11 to one side beyond the thin-walled portion 4, and then recessing a portion of this solid columnar portion 11 to the other side, causing the plastically flowing portion to protrude further to one side in a cylindrical shape, and then bending this cylindrical portion 13 in a curled shape toward the thin-walled portion 4. This allows the protective cover 5 to protect the thin-walled portion 4 while leaving a base column portion 12 in the pressure-receiving portion 3 with a thickness that allows the effects of corrosion when foreign matter adheres to be negligible.

The thin-walled portion 4 also has a rupture groove 6 that is engraved with a depth in the thickness direction so as to pass through the area between the pressure-receiving portion 3 and the surrounding plate portion 2. This means that the rupture groove 6 is located on the pressure-receiving portion 3 side relative to the tip portion 7 of the protective cover 5, and the particularly thin rupture groove 6 can be protected by the protective cover 5.

In addition, the thickness of the metal plate is 2.0 mm or more, and more preferably greater than 3.0 mm and less than 5.0 mm, so that the entire valve 1 can be formed by pressing using a progressive die.

In the first embodiment, it is important to narrow the gap between the tip 7 of the protective cover 5 and the surrounding plate 2 shown in FIG. 4. However, in the process of curling the protective cover 5 as shown in FIG. 9, there is a concern that the thin-walled portion 4 may crack when the punch P4 hits the workpiece W. Therefore, there is a limit to forming the protective cover 5 into a curled shape, that is, narrowing the gap between the tip 7 of the protective cover 5 and the surrounding plate 2 shown in FIG. 4. For this reason, if you want to further improve the protective performance of the thin-walled portion 4, you can add a part to the metal plate to prevent foreign matter from entering. As an example, a second embodiment is shown in FIG. 10. In the following, only the differences from the first embodiment will be described.

The thin-walled portion 4 in the second embodiment has a ridge 8 that protrudes to one side along the tip 7 of the protective cover 5. The ridge 8 surrounds the rupture groove 6 and continues at a constant height around its entire circumference.

The surrounding plate portion 2 has a protective wall 9 that protrudes to one side along the tip portion 7 of the protective cover 5. The protective wall 9 surrounds the tip portion 7 of the protective cover 5 and is continuous at a constant height around the entire circumference.

The gap between the protective cover 5 and the ridge 8, and the gap between the protective cover 5 and the protective wall 9 should each be as narrow as possible within the limits of press working. Taking into consideration the feasibility of press working, the ability to prevent foreign matter from entering, and the assurance of the rupture pressure of the valve 1, it is preferable that the dimensions of each of these gaps be 1.0 mm or more and 3.0 mm or less.

The protrusions 8 and protective walls 9 can be press-formed by adding concave surfaces for forming the protrusions 8 and protective walls 9 to the upper die D2 shown in FIG. 5. In this case, the shape and stroke of punch P4 can be appropriately changed so that punch P4 does not strike the protrusions 8 and protective walls 9 in the curling process shown in FIG. 9.

The battery lid according to the second embodiment has a labyrinth formed by the protective cover 5 and the protrusion 8 that protrudes to one side along the tip 7 of the protective cover 5. Therefore, even if a foreign object enters through the opposing gap between the tip 7 and the surrounding plate portion 2, the protrusion 8 can prevent the foreign object from entering.

In addition, the battery lid according to the second embodiment has a labyrinth formed by the protective cover 5 and the protective wall 9 that protrudes to one side along the tip 7 of the protective cover 5, so that the protective wall 9 can prevent foreign matter from entering the opposing gap between the tip 7 and the surrounding plate portion 2.

It is not necessary to use both the ridge 8 and the protective wall 9 as in the second embodiment, and using only one of them can protect the thin-walled portion 4 better than in the first embodiment.

In addition, in the above embodiment, the valve 1 (pressure receiving portion 3 and thin wall portion 4) is circular, but it is also possible to mold the protective cover even if the valve is oval or rectangular.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. Therefore, the scope of the present invention is defined by the claims, and it is intended to include all modifications within the scope and meaning equivalent to the claims.

Reference Signs List 1 Valve 2 Surrounding plate 3 Pressure receiving portion 4 Thin wall portion 5 Protective cover 6 Rupture groove 7 Tip portion 8 Ridge 9 Protective wall

Claims (5)

A battery cover made of a metal plate having a valve that breaks open when a predetermined pressure is applied and a surrounding plate portion connected to the valve, the battery cover comprising:
the valve includes a pressure receiving portion protruding to one side, and a thin-walled portion that is thinner than the pressure receiving portion and the surrounding plate portion and connects the pressure receiving portion to the surrounding plate portion,
The valve begins to tear from the thinned portion when the predetermined pressure is reached,
The battery lid, wherein the pressure-receiving portion has a protective cover extending into the air so as to cover the thin-walled portion from one side. The pressure-receiving portion has a solid columnar base portion protruding to one side from the thin-walled portion,
2. The battery lid according to claim 1, wherein the protective cover protrudes high in a cylindrical shape from the base portion of the pressure receiving portion to one side, and the cylindrical tip side is curled toward the thin portion. The battery cover according to claim 1 or 2, wherein the thin-walled portion has a rupture groove engraved with a groove depth in the thickness direction so as to pass through the area between the pressure-receiving portion and the surrounding plate portion. A battery lid according to any one of claims 1 to 3, wherein the thin-walled portion has a protrusion that protrudes to one side along the tip of the protective cover. A battery lid according to any one of claims 1 to 4, wherein the surrounding plate portion has a protective wall that protrudes to one side along the tip of the protective cover.

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