JP3848438B2 - Method for manufacturing explosion-proof sealing plate for sealed battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is used for sealing a battery case opening in a sealed non-aqueous electrolyte battery having a high energy density such as a sealed battery, particularly a lithium secondary battery, and the battery internal pressure rises to a set value. Explosion-proof seal for sealed batteries with a function to completely cut off the energizing currentPlankIt relates to a manufacturing method.
[0002]
[Prior art]
In recent years, electronic devices such as AV devices and personal computers are rapidly becoming portable and cordless. Especially, as a drive power source for portable devices such as watches and cameras, various types of alkaline storage batteries and lithium secondary batteries with high capacities are used. Non-aqueous electrolyte (organic solvent-based electrolyte) secondary batteries typified by batteries are suitable. Furthermore, these non-aqueous electrolyte secondary batteries should be sealed with high energy density and excellent load characteristics. Has been promoted.
[0003]
By the way, in a sealed nonaqueous electrolyte battery having a high energy density, a so-called Neumann method that consumes gas generated inside the battery as a counter electrode cannot be adopted, and it is necessary to avoid overcharge and overdischarge. However, when an external short circuit occurs due to overcharge or misuse due to failure of related equipment including a charger, the power generation element inside the battery causes a chemical reaction, for example, due to an abnormal reaction due to overcharge or short circuit. The electrolytic solution and the active material are decomposed, and gas is abnormally generated inside the battery as the internal heat is generated, so that the internal pressure of the battery becomes excessive. In order to prevent such problems from occurring in advance, this type of battery has conventionally been provided with an explosion-proof safety mechanism that opens the valve body and discharges gas when the internal pressure of the battery exceeds a set value. ing. Furthermore, in a non-aqueous electrolyte secondary battery, a charging current continues to flow in an overcharged state, so the electrolyte and active material may continue to decompose and the temperature may rise rapidly. Therefore, conventionally, this type of battery is provided with a reliable explosion-proof safety mechanism that completely cuts off the energization current prior to gas discharge by detecting that the internal pressure of the battery has increased to a predetermined value. .
[0004]
As an explosion-proof sealing plate provided with such an explosion-proof safety mechanism, for example, one having a configuration as shown in FIG. 5 has been proposed. (Japanese Patent Application No. 7-282762). In this explosion-proof sealing plate, the lower metal foil valve body 1 and the upper metal foil valve body 2 are overlapped with each other with an insulating gasket 3 interposed between the peripheral portions thereof, and upward of the lower metal foil valve body 1. A welded portion in which the central portions of the convex portion 1a having a circular shape in a plan view bulging in a curved shape and the concave portion 2a having a circular shape in a plan view bulging downwardly from the upper metal foil valve body 2 are welded to each other. Electrical connection is made only through 4. In normal times, the energizing current is connected to the electrode plate (not shown), the lead body 7, the metal case 8 and the lower metal foil valve body 1 through the welded portion 4 to the upper metal foil valve body 2, the conductive spacer 9 and the positive terminal. It flows in the energization path to the metal cap 10 that also serves as a battery and functions normally as a battery.
[0005]
When an abnormal situation occurs in the battery and the internal pressure of the battery rises, the pressure is transferred from the vent 8a of the metal case 8 through the vent hole (not shown) of the lower metal foil valve body 1 to the upper metal foil. The lower metal foil valve body 1 that acts as an upward pushing force on the valve body 2 and is connected to the upper metal foil valve body 2 via the welded portion 4 is further lifted by the upper metal foil valve body 2. Works. When the internal pressure of the battery rises above a predetermined value set by the breaking strength of the easily breakable portion 11 formed in the lower metal foil valve body 1 in a thin circular shape in plan view, the easily breakable portion 11 The two concave portions 2a receive a shearing force due to the stress that reverses the convex shape upward and break.
[0006]
Thereby, the portion surrounded by the easily breakable portion 11 in the convex portion 1a of the lower metal foil valve body 1 is hollowed out and separated from the lower metal foil valve body 1 integrally with the upper metal foil valve body 2, The energization path is opened and the energization current is interrupted to prevent the internal heat generation from continuing. Further, when the internal temperature of the battery continues to rise due to some cause and the internal pressure of the battery further increases, the thin-walled portion 12 having a C-shape in plan view of the upper metal foil valve element 2 is cleaved, and the gas flows into the metal cap 10. The gas is discharged from the gas discharge hole 13 to the outside of the battery.
[0007]
[Problems to be solved by the invention]
By the way, in the explosion-proof safety mechanism as described above, the setting of the battery internal pressure for interrupting the current, that is, the setting of the current interrupting pressure is particularly important for ensuring the safety of the secondary battery. In other words, if the current cutoff pressure is set too high, even if the current is cut off by detecting the battery internal pressure, the chemical reaction inside the battery will not stop and abnormal heat generation will continue. If it is set low, the current is cut off during heat generation during charging, which is a normal use condition, and the use period as a secondary battery is shortened, which is uneconomical. Therefore, in order to ensure both usability and safety as a secondary battery, it is necessary to interrupt the current reliably and stably within an appropriate pressure range of the battery internal pressure.
[0008]
Here, in order to reliably break the easily breakable portion 11 of the lower metal foil valve body 1 with the battery internal pressure set by the breaking strength, the lower metal foil valve body 1 and the upper metal foil valve body 2 are welded. It is an indispensable condition to be surely and stably connected via 4. For the formation of the welded portion 4, laser welding that can be formed with a strong welding strength is generally used. When this laser welding is performed, the convex portions 1 a and the concave portions of the valve bodies 1 and 2 are used. It is necessary to stably hold the welded portions of 2a in close contact with each other. Therefore, in order to ensure a required contact state between the parts to be welded, both valve bodies 1 and 2 are sandwiched from both sides by a jig such as a presser pin and are brought into contact at a constant pressure.
[0009]
However, if it is sandwiched too much by a jig, the convex portion 1a or the concave portion 2a is abnormally deformed to form a gap between the welded parts, and heat from one member irradiated with laser light to the other member Conduction becomes insufficient, the welded portion 4 formed has a variation in weld strength, and further, poor welding may occur. The variation in the welding strength of the welded portion 4 is a variation in the pulling force of the lower metal foil valve body 1 by the upper metal foil valve body 2 at the same battery internal pressure, that is, a variation in the current interrupting pressure. When the predetermined value set by the breaking strength is reached, the current cannot be reliably interrupted.
[0010]
On the other hand, when the pinching by the jig is too small, the contact area between the convex portion 1a and the concave portion 2a is smaller than the laser spot diameter and the welding strength is lowered. For this reason, the conventional sealed explosion-proof sealing plate cannot obtain high reliability in the current interrupting pressure. In addition, when the contact area between the convex portion 1a and the concave portion 2a is too small, depending on the energy density of the laser beam, it becomes easy to make a hole in the laser irradiation portion. In particular, if the concave portion 2a has a hole, the upper metal foil The sealability by the valve body 2 cannot be ensured, and a defect in which the current interruption function cannot be obtained occurs.
[0011]
FIG. 5 shows an explosion-proof sealing plate applied to the sealing of a cylindrical battery. The convex part 1a and the concave part 2a of both valve bodies 1 and 2 correspond to a battery case having a circular opening. Both are formed in a circular shape in plan view. On the other hand, in a rectangular battery, since the battery case has a substantially rectangular shape with a horizontal cross section, the metal case of the explosion-proof sealing plate for this battery has a long and substantially rectangular horizontal cross section shape corresponding to the battery case, That is, the length of the opening is formed in a container shape that is much larger than the width.
[0012]
Therefore, the concave portion having a circular shape in plan view formed on the upper metal foil valve body of the sealing plate is extremely small because the diameter thereof is regulated by the width dimension of the metal case. As a result, as the pressure receiving area of the concave portion decreases, the pressure required to invert the concave portion increases, and the easily breakable portion is set to the battery internal pressure set by its breaking strength, that is, the set current cutoff pressure. There is a problem that it cannot be broken.
[0013]
  Therefore, the present invention eliminates the above-mentioned problems, provides a structure capable of reliably and stably welding the upper and lower valve bodies, and provides a highly reliable current interruption function. Sealed explosion-proof sealing plate that can reliably break currentManufacturing methodIs intended to provide.
[0019]
[Means for Solving the Problems]
  In order to solve the above-mentioned problem, the claim 1The manufacturing method of the explosion-proof sealing plate for a sealed battery according to the invention is such that both upper and lower metal foil valve bodies having conductivity and flexibility are overlapped with each other with an insulating gasket interposed between the peripheral portions. Before or after the step of inserting into the metal sealing case and the step of inserting the both metal foil valve bodies into the sealing case, the peripheral edge of each of the metal foil valve bodies is a pair of holding jigs. In the state of sandwiching and fixing the insulating gasket and further through the sealing case, and in the state of sandwiching and fixing both the metal foil valve bodies, at least one tip portion of the pair has a curved portion around the central flat portion. By operating the pair of forming pins having the shape having the upper opening portion and the bottom vent hole in the sealing case in directions close to each other without being inserted, respectively, The both metal foil valve bodies are press-molded at the same time with both molding pins, and the concave portion and the convex portion that are in close contact with each other are molded into the two metal foil valve bodies; The step of welding the contact portion with the convex portion by laser welding to form a connection portion, and after sequentially superposing a conductive spacer and a metal cap on the upper metal foil valve body, the opening portion of the sealing case And inwardly caulking.
[0020]
  In this manufacturing method, at least one of the concave portion of the upper metal foil valve body or the convex portion of the lower metal foil valve body is a cross-section inverted trapezoid shape or a cross-section trapezoid shape that is curved from the periphery of the central flat surface and extends obliquely. Can be easily and reliably formed, and the center of each of the concave and convex portions of both metal foil valve bodies has an area larger than the spot diameter of the laser beam irradiated from the laser welding machine. In addition, it is possible to stably form a contact surface that is elastically in close contact with no gap. Therefore,The easily breakable portion can be reliably broken at the battery internal pressure set by its breaking strength, and high reliability can be obtained for the current breaking pressure.An explosion-proof sealing plate for a sealed battery can be manufactured easily and with high productivity.
[0021]
  The invention of claim 2The method for manufacturing an explosion-proof sealing plate for a sealed battery is a method in which both upper and lower metal foil valves having conductivity and flexibility are overlapped with an insulating gasket interposed between the peripheral portions. Before or after the step of inserting into the sealing case and the step of inserting both the metal foil valve bodies into the sealing case, the lower metal foil is provided with a concave portion that bulges downward in the upper metal foil valve body. Forming a convex portion that bulges upward in the valve body and bringing the central portions of the concave portion and the convex portion into contact with each other; and an upper opening and a bottom vent in the sealing case And increasing the contact area between the concave portion and the convex portion by applying pressurized gas to the concave portion and the convex portion, respectively, and contact between the concave portion and the convex portion. Weld the parts with laser welding to A step of forming, after which said upper metal Hakuben allowed on sequentially superimposed conductive spacer and a metal cap body, and a, a step of caulking the opening portion of the sealing case inward.
[0022]
  In this manufacturing method, after both the metal foil valve bodies are preliminarily molded with a concave portion and a convex portion whose central portions are in contact with each other, the two valve bodies are made to sandwich the valve bodies with pressurized gas. As a result, the contact surface where the concave portion and the convex portion are elastically in close contact with each other is gradually increased, so that the area between the concave portion and the convex portion is larger than the spot diameter of the laser beam. The contact surface can be formed very smoothly. As a result, even in this manufacturing method, it is possible to form a required connection portion having a uniform welding strength with a high yield.The easily breakable part can be reliably broken at the battery internal pressure set by its breaking strength, and high reliability can be obtained for the current breaking pressure.An explosion-proof sealing plate for a sealed battery can be manufactured easily and with high productivity.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an explosion-proof sealing plate for a sealed battery according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. In this embodiment, a sealing plate for sealing the opening of a rectangular sealed battery is illustrated, and therefore FIG. 1 is a cut along the length direction of the sealing plate whose horizontal cross section is an elongated rectangular shape. FIG. 2 is a longitudinal sectional view taken along a cutting line along the width direction.
[0024]
The explosion-proof sealing plate includes a thin upper metal foil valve body 17 having flexibility and conductivity, and a thin lower metal foil valve body 18 having flexibility and conductivity, which is opposed to the upper metal foil valve body 17. An insulating gasket 19 interposed between the peripheral portions of both valve bodies 17, 18, a conductive spacer 20 superimposed on the upper surface of the peripheral portion of the upper metal foil valve body 17, and the conductive spacer 20 And a metal cap 21 having a plurality of exhaust holes 21a, and a sealing case 22 made of aluminum having a plurality of vent holes 22a and holding each of the above members in a stacked state. .
[0025]
The upper metal foil valve body 17 is formed of an elongated rectangular aluminum thin plate having a thickness of 0.06 mm, a length of 27.3 mm, and a width of 3.5 mm, and a concave portion 23 bulging downward at the center thereof and the concave shape. An easily breakable thin-walled portion 24 formed by using a substantially C-shaped stamp around the portion 23. The concave portion 23 is formed in a rectangular shape in plan view corresponding to the shape of the upper metal foil valve body 17. For example, the length dimension L shown in FIG. 1 is 20 mm, the width dimension D shown in FIG. The protrusion length from the lower surface of the part is set to 0.36 mm. That is, as is clear from a comparison between FIG. 1 and FIG. 2, the concave portion 23 has a longitudinal cross-sectional shape that is longer than a longitudinal cross-sectional shape in the width direction. Further, the concave portion 23 has a flat surface 23a having a rectangular shape in plan view at the bottom bulging downward, and is a pressure-receiving surface in the length direction that curves from the peripheral end portion of the flat surface 23a and extends obliquely upward. 23B and the pressure receiving surface 23b in the width direction are molded into a shape.
[0026]
Accordingly, the concave portion 23 has a substantially inverted trapezoidal shape in both the cross-sectional shape along the cutting line along the length direction shown in FIG. 1 and the cross-sectional shape along the cutting line along the width direction shown in FIG. Yes.
[0027]
On the other hand, the lower metal foil valve body 18 is made of an elongated rectangular aluminum thin plate having a thickness of 0.08 mm, a length of 27.8 mm, and a width of 4 mm. A convex portion 27 bulging upward is provided at a location facing the concave portion 23 in the lower metal foil valve body 18, and the convex portion 27 has a pair of cut lines parallel to each other at an interval of 1.8 mm. By forming it in the width direction, it becomes a square shape with a side of 1.8 mm. Furthermore, since the convex part 27 bulges upward in the width direction, a pair of ventilation holes 28, 28 are formed on both sides of the convex part 27 by cut lines. Further, as shown in FIG. 2, a pair of easily breakable portions 29 formed in a thin wall having a predetermined breaking strength are disposed at both ends of the convex portion. Both valve bodies 17 and 18 are brought into an electrically conductive state only through a connection portion S that is welded to each other by locally laser-welding a contact portion between the flat surface 23 a of the concave portion 23 and the convex portion 27. It is connected. The valve bodies 17 and 18 are housed in the sealing case 22 with the connecting portion S facing the vent 22a.
[0028]
The sealing plate is inserted into the sealing case 22 in a state where the valve bodies 17 and 18 are overlapped with each other with an insulating gasket 19 interposed between the peripheral portions thereof, and then the flat surface 23a of the concave portion 23 and the convex surface 23a. The connecting portion S is formed by locally laser welding the contact portion with the shaped portion 27, and then the conductive spacer 20 and the metal cap 21 are sequentially inserted into the sealing case 22 and the upper metal foil valve body 17 is The upper part of the sealing case 22 is caulked inward in a state of being overlapped with each other. The upper portion of the insulating gasket 19 that is bent inward during the caulking process of the sealing case 22 is interposed between the sealing case 22 and the metal cap 21 to insulate them. In this sealing plate, after a positive electrode lead body (not shown) is connected to the sealing case 22, as shown by a two-dot chain line in FIG. The battery case 31 is inserted into an opening of the battery case 31 and supported by an annular support part 32 protruding inward of the battery case 31. After that, the upper end portion of the battery case 31 is caulked inward, so that the sealing plate seals the battery case 31.
[0029]
Next, the operation of the above-described sealed battery explosion-proof sealing plate will be described. The energization current reaches from the positive electrode plate (not shown), the positive electrode lead body, the sealing case 22 and the lower metal foil valve body 18 to the upper metal foil valve body 17, the conductive spacer 20 and the metal cap 21 through the connection portion S. It flows in the current path and functions normally as a battery. By the way, in the case of a lithium secondary battery or the like when an uncontrolled overcharge or short circuit occurs due to a failure of the charger, the battery allowable pressure is often exceeded and the battery internal pressure increases. In this case, if a current continues to flow through the battery, the battery temperature may rapidly increase with decomposition of the electrolyte and the active material, and an excessive amount of gas or vapor may be generated. Thus, an explosion-proof safety function that detects the internal pressure of the battery and completely cuts off the energized current acts.
[0030]
That is, the battery internal pressure acts as a pushing force from the vent 22 a of the sealing case 22 to the pressure receiving surfaces 23 A and 23 a of the concave portion 23 through the pair of vent holes 28 and 28 of the lower metal foil valve body 18. When the internal pressure of the battery rises to a predetermined value set by the sum of the breaking strengths of the pair of easily breakable portions 29, 29 of the lower metal foil valve body 18, the recessed portion 23 is reversed and deformed into a convex shape upward. Then, the convex portion 27 of the lower metal foil valve body 18 is pulled up, a shearing force acts on the easily breakable portions 29, 29, and the easily breakable portions 29, 29 are broken. Thereby, since the convex part 27 is integrated with the upper metal foil valve body 17 and separated from the lower metal foil valve body 18, both the valve bodies 17, 18 that are conducted only through the connection part S are separated from each other. The energization path is interrupted and the energization current is also interrupted to prevent continuation of internal heat generation. Here, the thin-walled portion 24 of the upper metal foil valve body 17 is set to have a higher rupture strength than the easily breakable portion 29, and the upper metal foil valve body 17 maintains the state as it is when the current is interrupted, so that the battery case In order to prevent the electrolytic solution in 31 from leaking out, it does not occur that the electrolytic solution leaks to the outside and corrodes the battery equipment.
[0031]
Even if the current is interrupted as described above, a large amount of gas or vapor is generated when the internal pressure of the battery continues to increase without stopping the increase in the internal temperature of the battery for some reason. Thereby, when the internal pressure of the battery reaches a predetermined value set by the breaking strength of the thin portion 24 of the upper metal foil valve body 17, the thin portion 24 is cleaved, and the filled gas is discharged from the exhaust hole 21 a of the metal cap 21. To the outside of the battery. Here, the convex portion 27 has a smaller shape than the portion surrounded by the C-shaped thin portion 24 in the upper metal foil valve body 17 and is opposed to the relative position included in the thin portion 24. ing. Therefore, the convex portion 27 that is separated and attached to the upper metal foil valve body 17 does not block the gas discharge hole that is opened due to the breakage of the thin portion 24 in the upper metal foil valve body 17, and a large amount of gas is generated. Sometimes internal gas can be quickly discharged outside.
[0032]
This explosion-proof sealing plate has a configuration that can reliably and stably weld the concave portions 23 and the convex portions 27 of both valve bodies 17 and 18 to form a connection portion S having no variation in welding strength. That is, the concave portion 23 of the upper metal foil valve body 17 is formed into a substantially inverted trapezoidal shape in both the cross-sectional shape along the cutting line along the length direction and the cross-sectional shape along the cutting line along the width direction. And a flat surface 23a at the bottom. Therefore, when the sealing plate is assembled, when the two metal foil valve bodies 17 and 18 are overlapped with each other with the insulating gasket 19 interposed between the peripheral portions, the lower metal foil valve body 18 bulges upward in a curved shape. The convex portion 27 molded into the shape to be deformed so that the central portion thereof is along the flat surface 23a and is in close contact with the flat surface 23a. Therefore, a contact surface having an area larger than the spot diameter of the laser beam and elastically adhering without a gap is stably formed between the flat surface 23a and the convex portion 27. By irradiating laser beams onto each other and welding them together, it is possible to form a required connection portion S having no variation in welding strength with good yield while preventing poor welding and occurrence of drilling.
[0033]
Further, when the explosion-proof sealing plate is applied to a prismatic battery as in this embodiment, the pressure required to reverse the concave portion 23 of the upper metal foil valve element 17 can be set low, In combination with the connection portion S having no variation in welding strength, high reliability can be obtained for the current interrupting pressure set by the breaking strength of the easily breakable portion 29. That is, the concave portion 23 of the upper metal foil valve body 17 corresponds to a rectangular battery having an elongated rectangular opening, and has a rectangular shape in plan view in which the cross-sectional shape in the length direction is much longer than the cross-sectional shape in the width direction. Compared to a conventional sealing plate having a circular concave portion with a radius corresponding to the width dimension of the rectangular battery, the cross-sectional shape in the length direction is larger than the cross-sectional shape in the width direction. Thus, the area of the pressure-receiving surface 23B in the length direction is increased. As a result, the pressure required to invert the concave portion 23 of the upper metal foil valve body 17 can be set lower as the area of the pressure receiving surface 23B becomes larger. When the predetermined value set by the breaking strength of the portion 29 is reached, it can be reliably reversed.
[0034]
Next, a method for manufacturing the explosion-proof sealing plate will be described. The manufacturing method according to an embodiment of the present invention is different from the conventional method only in the step of forming the concave portion 23 and the convex portion 27 on the valve bodies 17 and 18 prior to the formation of the connection portion S, respectively. It is. That is, as shown in FIG. 3, a lower metal foil valve body 18 in which a pair of cut lines and an easily breakable portion 29 are formed in advance, an insulating gasket 19, and an upper metal foil valve body 17 in which a thin portion 24 is formed in advance are sealed in a sealing case. 22 are sequentially inserted, and both valve bodies 17 and 18 are overlapped with each other with an insulating gasket 19 interposed between their peripheral portions.
[0035]
Next, the cylindrical lower presser jig 33 and the upper presser jig 34 are respectively brought into pressure contact with the peripheral portions of the sealing case 22 and the upper metal foil valve body 17 to insulate the peripheral portions of the valve bodies 17 and 18. The gasket 19 is interposed and fixed. Subsequently, the lower molding pin 37 and the upper molding pin 38 are actuated in directions close to each other as indicated by arrows, so that both the valve bodies 17 and 18 are press-molded simultaneously. Here, the lower molding pin 37 is substantially hemispherical in cross-sectional shape in the width direction at the tip portion, and the upper molding pin 38 has a curved portion 38b around a rectangular flat portion 38a in the plan view of the tip. ing. The lower molding pin 37 is inserted through the vent 22a of the sealing case 22 to press the lower metal foil valve body 18 without any trouble.
[0036]
Accordingly, the upper metal foil valve body 17 is plastically deformed by pressurization by the upper forming pin 38, whereby the flat surface 23a is curved by the flat portion 38a and the periphery of the flat surface 23a is curved by the curved portion 38b. The surfaces 23B and 23b are respectively molded to obtain the concave portion 23 shown in FIGS. On the other hand, the lower metal foil valve body is plastically deformed by pressurization with the lower molding pin 37, and the central portion of the convex portion 27 is pressed while being deformed along the flat surface 23a of the concave portion 23. The convex portion 27 bulging upward is formed and processed, and the bulge of the convex portion 27 forms a pair of vent holes 28, 28 on both sides of the convex portion 27. Therefore, between the flat surface 23A and the convex portion 27, a contact surface having an area larger than the spot diameter of the laser beam and elastically adhering without a gap is stably formed.
[0037]
When the above-described forming of the concave portion 23 and the convex portion 27 is completed, the connection portion S is formed by irradiating the contact portion between the concave portion 23 and the convex portion 27 with laser light from a laser welding machine. In this laser welding, it is possible to easily identify the quality of the welded state from below through the vent 22a of the sealing case 22 while performing welding by irradiating the upper metal foil valve body 17 with laser light from above. At the same time, since the air vent 22a functions as a space for heat escape, stable welding can be performed, and a required connecting portion S without variation in welding strength can be formed with high yield. In addition, welding can also be performed by irradiating the lower metal foil valve body 18 with laser light from below through the vent 22a. After forming the connection portion S, the conductive spacer 20 and the metal cap 21 are sequentially inserted into the sealing case 22 and overlapped on the upper metal foil valve body 17 in the same manner as in the conventional method, and the sealing is performed in this state. A sealing plate is completed by caulking the upper portion of the case 22 inward.
[0038]
FIG. 4 is a longitudinal sectional view showing a process of forming the concave portion 23 and the convex portion 27 on the valve bodies 17 and 18 in the method for manufacturing an explosion-proof sealing plate for a sealed battery according to another embodiment of the present invention. It is. In this manufacturing method, both the valve bodies 17 and 18 are inserted into the sealing case 22 in a state where the valve bodies 17 and 18 are overlapped with the peripheral edge portions of the valve bodies 17 and 18 interposed therebetween, and then the central portions of the both valve bodies 17 and 18 are inserted. Are clamped from both sides by an existing jig such as a presser pin and brought into contact with each other, and the temporary concave portion 23 and the convex portion 27 are preliminarily molded as shown in FIG.
[0039]
Next, a pair of gas discharge nozzles 39 and 40 are disposed so as to oppose the vent 22a of the sealing case 22 and the opening of the sealing case 22, respectively, and the laser welding machine 41 is contacted between the valve bodies 17 and 18. Place it toward the. Then, pressurized gas G is discharged from both nozzles 39 and 40 to pressurize the concave portion 23 and the convex portion 27 in directions close to each other, and laser light R is emitted from the laser welding machine 41 in the pressurized state. Then, the contact portions of both valve bodies 17 and 18 are laser welded to each other to form the connection portion S. At the time of this welding, the contact surface where the concave portion 23 and the convex portion 27 are elastically closely contacted with no gap by the sandwiching action by the pressurized gas G smoothly increases, and the area larger than the spot diameter of the laser beam is increased. A contact surface is formed, and laser welding is performed on the contact surface. Thereby, the required connection part S without variation in welding strength can be formed with good yield, and the explosion-proof sealing plate shown in FIGS. 1 and 2 can be obtained.
[0042]
【The invention's effect】
  According to the method of manufacturing an explosion-proof sealing plate for a sealed battery of the present invention, an area larger than the spot diameter of the laser beam of the laser welding machine is provided in the central part of each of the concave part and the convex part of both metal foil valve bodies. And can stably form a contact surface that is elastically adhered without gaps,The easily breakable portion can be reliably broken at the battery internal pressure set by its breaking strength, and high reliability can be obtained for the current breaking pressure.An explosion-proof sealing plate for a sealed battery can be easily manufactured with high productivity.
[0043]
  According to another method for manufacturing an explosion-proof sealing plate for a sealed battery of the present invention, after forming a concave portion and a convex portion that are in contact with each other at the central portion of each of the metal foil valve bodies, By acting so that both valve bodies are sandwiched, the contact surface where the concave portion and the convex portion are elastically closely contacted with no gap is increased, so the laser beam is interposed between the concave portion and the convex portion. The contact surface having an area larger than the spot diameter can be formed very smoothly, and a required connection portion having no variation in welding strength is formed with a high yield.The easily breakable portion can be reliably broken at the battery internal pressure set by its breaking strength, and high reliability can be obtained for the current breaking pressure.An explosion-proof sealing plate for a sealed battery can be manufactured easily and with high productivity.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view taken along a cutting line in a length direction showing an explosion-proof sealing plate for a sealed battery according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a longitudinal cross-sectional view showing main steps of a method for manufacturing an explosion-proof sealing plate for a sealed battery according to an embodiment of the present invention.
FIG. 4 is a longitudinal sectional view showing main steps of a method for manufacturing an explosion-proof sealing plate for a sealed battery according to another embodiment of the present invention.
FIG. 5 is a longitudinal sectional view of a conventional explosion-proof sealing plate for a sealed battery.
[Explanation of symbols]
17 Upper metal foil disc
18 Lower metal foil valve
19 Insulation gasket
20 Conductive spacer
21 Metal cap
22 Sealing case
22a Vent
23 Concave part
23a flat surface
23B, 23b Pressure receiving surface
27 Convex part
29 Easy break
31 Battery case
33 Lower presser jig
34 Upper presser jig
37 Lower molding pin
38 Upper molding pin
38a Plane part
38b Curved part
39, 40 Gas discharge nozzle
41 Laser welding machine
S connection
G Pressurized gas

Claims (2)

Inserting both conductive and flexible upper and lower metal foil valve bodies into a metal sealing case in a state of being overlapped with an insulating gasket interposed between the respective peripheral edges;
Before or after the step of inserting the two metal foil valve bodies into the sealing case, a peripheral edge of each of the two metal foil valve bodies is interposed between the insulating gasket and further the sealing case by a pair of holding jigs. Sandwiching and fixing, and
In a state in which both the metal foil valve bodies are sandwiched and fixed, a pair of forming pins in which at least one tip portion of the pair has a curved portion around a central flat portion is formed as an upper opening in the sealing case. The both metal foil valve bodies are simultaneously press-molded with the both molding pins by inserting the vents in the top and bottom portions or operating them in the directions close to each other without being inserted. Forming a concave portion and a convex portion that are in close contact with each other, respectively,
Forming a connection portion by welding a contact portion between the concave portion and the convex portion by laser welding;
A step of caulking the opening of the sealing case inward after sequentially superposing a conductive spacer and a metal cap on the upper metal foil valve body;
The manufacturing method of the explosion-proof sealing board for sealed batteries which has this. Inserting both conductive and flexible upper and lower metal foil valve bodies into a metal sealing case in a state of being overlapped with an insulating gasket interposed between the respective peripheral edges;
Before or after the step of inserting the two metal foil valve bodies into the sealing case, a concave portion that bulges downward on the upper metal foil valve body, and a convex shape that bulges upward on the lower metal foil valve body. Forming each part, and contacting each central part of the concave part and the convex part;
Increasing the contact area between the concave portion and the convex portion by applying a pressurized gas to the concave portion and the convex portion through the upper opening and the bottom vent in the sealing case;
Forming a connection portion by welding a contact portion between the concave portion and the convex portion by laser welding;
A step of caulking the opening of the sealing case inward after sequentially superposing a conductive spacer and a metal cap on the upper metal foil valve body;
The manufacturing method of the explosion-proof sealing board for sealed batteries which has this.

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