JPH08293293A - Safety device for sealed battery - Google Patents

Abstract

PURPOSE: To eliminate a welded part from a current interrupting mechanism and to facilitate adjustments and settings for switching from connection to interruption of current in relation to a set internal pressure value. CONSTITUTION: An opening 1a in a battery can 1 is sealed by caulking the circumference of a sealing body 2 via an insulating gasket 5. The sealing body comprises a rigid sealing cover 6 made from a conducting material to the lower surface 6a of which a lead wire 4 from a power generating element 3 is connected and whose first through hole 11 is sealed by an elastic film 12; a safety valve 10 made from a conducting material whose end face 10a is made to face the first through hole and abut to the sealing cover so that it is electrically connected; a holding member 8 made from a conducting material which is stacked along with the sealing cover and an insulating ring 7 and which makes the safety valve fit into a second through hole 13 to hold the valve by means of sliding friction resisting forces between the peripheral surfaces of both; and a cap-shaped positive terminal 9. By setting the outside diameter of the safety valve, the sliding friction resisting forces are made smaller than pressure on the safety valve derived from the internal pressure of the battery can, i.e., a first set internal pressure value, and when the first set internal pressure value is exceeded the safety valve makes relative upward movement and leaves the state of abutting to the sealing cover; as the internal pressure further builds up, the elastic film is ruptured to release the internal pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed battery safety device for coping with an abnormal situation such as an abnormal rise in internal pressure due to overcharge or the like in a sealed battery such as a secondary battery.

[0002]

2. Description of the Related Art Conventionally, as a safety device for this type of sealed battery, a lead plate to which a lead wire from a power generating element is connected is attached to an inner surface of an insulating plate, and the through hole at the center of the insulating plate is formed by the lead plate. A disk-shaped flexible explosion-proof valve formed of a conductive material is provided so as to cover the insulating plate,
It is known that a protrusion at the center of the explosion-proof valve is fitted in the through hole and the lead plate is ultrasonically welded to the protrusion (for example, JP-A-2-112151 and JP-A-2-288063). (See the official gazette). In these publications, the current is cut off when the protrusion is lifted by the increase of the internal pressure of the battery can and the lead plate is broken at the periphery of the through hole, or when the welded portion with the lead plate is peeled off. It is described that it is done.

As another conventional safety device for a sealed battery, a disc-shaped valve holder made of a conductive material, to which lead wires are connected, and a protrusion at the central portion, which is covered with the disk-shaped valve holder, has the above-mentioned valve holder. A disc-shaped flexible valve body made of a conductive material spot-welded or ultrasonic-welded on the upper surface of the battery, and the space between the valve body and the valve holder communicates with the inside of the battery can. Known (for example, JP-A-6-140011)
(See the official gazette). In other words, in this device, the valve body is welded to the valve holding body to which the lead wire is connected, so as to avoid the inconvenience caused by directly welding the explosion-proof valve to the lead plate. And, in this publication, the pressure in the space also rises due to the rise of the internal pressure of the battery can, and the valve body is lifted upward, and the welding between the central protrusion and the valve holding body is removed to interrupt the current. Is listed.

And, when the internal pressure further rises,
The flexible explosion-proof valve or the flexible valve body is broken at a notch portion provided therein to allow internal gas or the like to escape to the outside, thereby preventing explosion of the battery itself.

[0005]

However, in the above-mentioned conventional safety device for a sealed battery, since the welding portion is used in the current interruption mechanism, the current interruption is ensured by the strength of the welding itself. There is a possibility that a situation that cannot be done will occur. That is, if the welding strength is too high, the valve does not separate from the valve holder even if the internal pressure rises, and as a result, the current cannot be shut off. Conversely, if the welding strength is too low, it will not be used during normal use. Due to a slight change in internal pressure or impact, the valve is separated from the valve holder, the current is cut off, and the valve becomes unusable.

As described above, in the conventional one, it is necessary to surely set the welding strength to a predetermined value. For that reason, if spot welding is performed by spot welding or the like, the spot welding will be performed during normal use. Since current is passed through the portion, the resistance may become too high and abnormal heat may be generated. On the contrary, if the welded portion is set in a circumferential shape, the weld strength increases in proportion to the welded area, and the above-mentioned inconvenience occurs.

Moreover, it is necessary to carry out a welding operation without excess or deficiency with respect to the predetermined welding strength in a mass production line as described above.
The process control becomes extremely difficult, variation between products is likely to occur, and reliability for products cannot be improved.

Further, if the internal pressure is released after the electric current is cut off, there is a possibility that the part which has been once peeled off or broken may return and come into contact with another conductive member.

The present invention has been made in view of the above circumstances, and an object of the present invention is to eliminate a welding portion from a current interruption mechanism of a safety device for a sealed battery and to provide a current for a predetermined internal pressure value. This is to facilitate the adjustment and setting for switching from connection to disconnection.

[0010]

In order to achieve the above object, the invention according to claim 1 is such that a power generating element is housed inside a battery can and provided in a sealing body for sealing an opening of the battery can. Is assumed. In this structure, the sealing body is made of a conductive material having a first through hole that opens to face the inside of the battery can, and the first through hole of the sealing lid is closed to seal the inside of the battery can. An insulating elastic film that
A piston-shaped safety valve made of a conductive material that relatively moves when the internal pressure of the battery can rises, and a holding member made of a conductive material having a second through hole for holding the safety valve in an internally fitted state. Then, while connecting the lead wire from the power generating element to the surface of the sealing lid facing the inside of the battery can, the outer peripheral edge portion is airtightly attached to the opening of the battery can to substantially oppose the internal pressure of the battery can. It is formed so as to have rigidity that does not deform. Further, the holding member is fixed in position in a state in which an outer edge portion of the opening portion of the battery can outside the sealing lid is overlapped with a surface of the sealing lid facing the outside of the battery can through an insulating member. To do. Further, the safety valve has a tip surface larger than the first through hole of the sealing lid, and contacts the surface of the sealing lid facing the outside of the battery can with the tip surface covering the first through hole. Are placed so that they are electrically connected. In addition, the outer peripheral surface of the safety valve and the inner peripheral surface of the second through hole resist the internal pressure of the battery can until the internal pressure of the battery can rises to reach the set internal pressure value, so that the safety valve moves relative to the sealing lid. While being held in a blocked state, they are closely fitted to each other so as to exert a sliding friction resistance force that relatively moves the safety valve to the side away from the sealing lid by the action of the internal pressure exceeding the set internal pressure value. It is a thing.

According to a second aspect of the present invention, in the first aspect of the present invention, the central portion of the sealing lid is bent and formed so as to be convex toward the inside of the battery can.

According to the invention of claim 3, in the invention of claim 1, the tensile rupture strength of the elastic film is set as a pressure value larger than a set internal pressure value for relatively moving the safety valve toward the side away from the sealing lid. It is set so that the battery can breaks when receiving the internal pressure of the battery can that exceeds the second set internal pressure value.

According to a fourth aspect of the invention, in the third aspect of the invention, the holding member is formed in a disk shape so as to shield the opening of the battery can, and has a gas vent hole penetrating inward and outward. To do.

According to a fifth aspect of the invention, in the invention according to the first or third aspect, an elastic film is attached to a surface of the sealing lid that faces the inside of the battery can and faces the inside of the battery can having the first through hole. It is arranged so as to seal the side opening.

According to a sixth aspect of the present invention, in the invention according to the first or third aspect, the sealing lid is composed of a pair of lid members each having a first through hole at the same position and overlapping each other in the inner and outer directions. Configure. Then, the elastic film is sandwiched between the opposed surfaces of the pair of lid members in a state where the elastic film is expanded by blocking between the first through holes of the pair of lid members, and is closely adhered to each other to be connected to the sealing lid. is there.

According to a seventh aspect of the invention, in the first aspect of the invention, the elastic film is joined in a state of being in close contact with the tip surface of the safety valve.

According to an eighth aspect of the present invention, in the first aspect of the present invention, the safety valve has the same cross-sectional shape from the base end to the front end and corresponds to the second through hole of the holding member, and from the inner surface of the holding member to the sealing lid side. It is composed of a columnar main body arranged so as to project to the above, and a head portion which is expanded from the base end side of the main body to the periphery and contacts the outer surface of the holding member.

According to a ninth aspect of the present invention, in the first aspect of the present invention, a PTC thermistor having a resistance value rapidly increasing in a set temperature range is provided in the middle of the current path between the lead wire and the sealing body. To do.

Further, in the invention described in claim 10, in the invention described in claim 1, as a sealing body, the sealing body is provided at an opening of the battery can and outside the holding member, and is electrically connected to the holding member. The positive electrode terminal is connected, the positive electrode terminal, the holding member in the state where the safety valve is fitted, the insulating member, and the sealing lid in the state where the tip surface of the safety valve is in contact with each other at the outer edge portions. It is configured so that they are preliminarily combined and integrated in a state of being polymerized with each other.

[0020]

According to the above-mentioned structure, according to the first aspect of the present invention,
When the internal pressure inside the battery can is lower than the set internal pressure value under normal use conditions with proper discharge and charging, even if the internal pressure acts on the tip surface of the safety valve through the elastic membrane, the outer circumference of the safety valve Since the sliding friction resistance between the surface and the inner peripheral surface of the second through hole of the holding member is larger than the internal pressure, relative movement of the safety valve is prevented against the internal pressure, and the safety valve and the lead wire. The contact with the sealing lid connected to is maintained. As a result, the electrical connection state is maintained.

On the other hand, when the internal pressure inside the battery can exceeds the set internal pressure value due to overcharging or the like, the internal pressure acts on the tip surface of the safety valve via the elastic membrane, and the safety valve is caused to move relatively based on the internal pressure. Since the pressing force applied becomes larger than the sliding frictional force, the safety valve relatively moves in the second through hole, and the contact between the tip end surface and the sealing lid is separated.
As a result, the electrical connection state due to the contact is cut off and switched to the electrical cutoff state, and the user of the battery can be made aware of the occurrence of the abnormality.

In this case, since the sealing lid has a rigidity that does not deform even if it receives the above-mentioned internal pressure, the internal pressure directly and effectively acts on the piston-like safety valve through the first through hole, and the relative movement of the safety valve is prevented. Done. Therefore, when an internal pressure rise that exceeds the set internal pressure value occurs, compared to the case where the internal pressure is indirectly applied to the entire conventional disc-shaped explosion-proof valve to cause bending deformation, the responsiveness is improved. It is possible to switch to the electrical cutoff state.

Moreover, in such a current interruption mechanism, switching between electrical connection and interruption according to the internal pressure inside the battery can is performed.
Since the sliding friction resistance between the safety valve and the second through hole is set, the setting and change of the setting are easier than the case of setting the tensile rupture strength of the welded portion as in the conventional sealed battery. Moreover, it can be reliably set to a predetermined value, and switching to an electrical cutoff state is ensured. Further, since the electrical connection and disconnection are switched by abutting instead of welding as described above, the process control during assembly can be facilitated and the reliability of the product can be improved.
Moreover, even in the electrical cutoff state, since the safety valve is held at that position by the sliding friction resistance force, it does not return.

According to the second aspect of the invention, in addition to the function of the first aspect of the invention, since the central portion of the sealing lid is formed to be convex toward the inside of the battery can, the bending As a result, the cross-sectional rigidity of the sealing lid is increased, and even if the sealing lid is thin, the sealing lid does not substantially deform against the internal pressure in the battery can.

According to the third aspect of the present invention, in addition to the action according to the first aspect of the invention, the tensile rupture strength of the elastic membrane causes the second set internal pressure value larger than the first set internal pressure value for relatively moving the safety valve. Since it is set to break when it receives an internal pressure that exceeds the internal pressure, when the internal pressure in the battery can rises and exceeds the first set internal pressure value, the safety valve first moves relative to contact the tip surface with the sealing lid. When the internal pressure rises and exceeds the second set internal pressure value,
The elastic film is broken and the gas inside the battery can is discharged through the first through hole, and as a result, the internal pressure of the battery can becomes atmospheric pressure. Therefore, in the event of an abnormality, the current is first interrupted to let the user of the battery know that the abnormality has occurred, and even if the user leaves it for a while, the internal pressure is released by degassing the inside to prevent further increase in the internal pressure. Therefore, destruction of the sealed battery is avoided.

According to the invention of claim 4, in addition to the function of the invention of claim 3, the holding member is formed in a disk shape so as to shield the opening of the battery can, and is a gas vent hole penetrating inward and outward. Therefore, even when the shape of the holding member is coupled to the inner peripheral portion of the opening portion of the battery can at the outer peripheral edge portion like the sealing lid, the above gas due to the breakage of the elastic film. The gas inside the battery can is discharged through the vent hole.

According to the invention of claim 5, in addition to the action of the invention of claim 1 or 3, the elastic film is attached to the surface of the sealing lid facing the inside of the battery can, and the first through hole is formed. Since it is arranged so as to seal the opening on the side facing the inside of the battery can, the sealing of the inside of the battery can by the sealing lid and the loading of the internal pressure through the first through hole on the tip surface of the safety valve are the safety valve. This can be done with the tip surface of the abutting contacting the sealing lid.

According to the invention of claim 6, in addition to the function of the invention of claim 1 or 3, the sealing lid is composed of a pair of lid members which are superposed on each other, and the elastic film is formed by the elastic film. The first and second through holes of the pair of lid members are blocked and hermetically sealed by being sandwiched between the facing surfaces of the members and closely contacting with the respective lid members. As in the case of 5, the internal sealing of the battery can and the loading of the internal pressure through the first through hole to the safety valve tip surface can be performed with the safety valve tip surface abutting the sealing lid. Moreover, the elastic film and the sealing lid are securely fixed to each other in position, and therefore, when the elastic film is broken, as in the invention described in claim 3, it is ensured that the elastic film and the sealing lid are broken at a predetermined tensile breaking strength. Become. Furthermore, since the elastic film is not provided on the surface facing the inside of the battery can, there is no restriction on the space for connecting the lead wires.
In addition to the operation according to the invention described in claim 1, since the elastic film is bonded in close contact with the tip surface of the safety valve, when the internal pressure in the battery can rises, the internal pressure is directly increased by the safety valve. It acts on the tip surface of the, and the switching to the electrical cutoff state due to the increase in the internal pressure can be performed with higher responsiveness.

According to the invention described in claim 8, in addition to the operation according to the invention described in claim 1, a safety valve has a columnar main body fitted in the second through hole and a base end side of the main body. Since it is formed of a head that contacts the outer surface of the holding member, the safety valve and the holding member are held by the head in the normal use state where the tip end surface of the safety valve is held in contact with the sealing lid. While the electrical connection area between the two can be increased, even if the safety valve relatively moves when the internal pressure of the battery can rises and exceeds the set internal pressure value, the outer peripheral surface of the main body at the position after the movement. Due to the sliding frictional resistance between the safety valve and the second through hole, the safety valve is held without coming off from the holding member.

In addition, in the invention described in claim 9, in addition to the function of the invention described in claim 1, a PTC thermistor is interposed in the middle of the current path between the lead wire and the sealing body. While the internal temperature of the battery can is at an appropriate temperature lower than the set temperature range in the normal use state where proper discharge and proper charge are performed, the resistance value of the PTC thermistor is kept at a small value and the lead wire and the sealing Current flows properly through the current path to and from the body. On the other hand, if the internal temperature rises above the set temperature range due to the occurrence of a short circuit, etc.,
Corresponding to the increase, the resistance value of the PTC thermistor sharply increases, and the power supply through the current path is substantially cut off.
Therefore, it is possible to add a safe operation even when the internal temperature is abnormal.

Further, in the tenth aspect of the invention, in addition to the function of the first aspect of the invention, a positive electrode terminal as a sealing body and a safety valve fitted and held in the second through hole are held. Since the holding member, the insulating member, and the outer peripheral portion of the sealing lid with the tip end surface of the safety valve in contact with each other are preliminarily combined and integrated with each other, the battery In addition to facilitating the assembling work to the opening of the can, it becomes possible to perform a test for confirming the operation of the safety valve separately from the battery can before the assembling.

[0032]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows a sealing portion of a safety device for a sealed battery according to a first embodiment of the present invention. In the figure, 1 is a battery can having an opening 1a, and 2 is a sealing body that closes the opening 1a and seals the battery can 1.

The battery can 1 is a metal can having a bottomed cylindrical shape (a cylindrical shape in the illustrated example, but may be a rectangular cylindrical shape), and a power generating element 3 is housed therein. There is. The power generating element 3 has a positive electrode plate, a negative electrode plate, an electrolytic solution, etc., and the other end of the lead wire 4 whose one end is connected to the positive electrode plate constitutes the above-described sealing body 2 with the other end. It is connected to the lower surface 6a of the lid 6 by means such as welding. A reduced diameter portion 1b is formed on the battery can 1 above the power generation element 3, and the sealing body is provided between the reduced diameter portion 1b and the upper end crimped portion 1c with the upper end opening edge crimped. The outer peripheral edge portion of 2 is airtightly sandwiched via the insulating gasket 5 to seal the battery can 1.

As shown in part in FIG. 2, the sealing body 2 has a disk-shaped sealing lid 6, a donut plate-shaped insulating ring 7, a disk-shaped holding member 8 and a cap-shaped. Positive terminal 9
And a piston-like safety valve 10. Then, the sealing body 2 is sandwiched by the upper end caulked portion 1c, so that the sealing lid 6, the insulating ring 7, the holding member 8 and the positive electrode terminal 9 are in close contact with each other in this order from the bottom and integrated into a superposed state. It has been assembled.

The sealing lid 6 is made of a conductive material such as aluminum, titanium, an alloy thereof, or stainless steel so that the central portion thereof has a bent convex portion 6b which is convexly bent inward of the battery can 1. Of the battery can 1 due to the increased cross-sectional rigidity due to the formation of the bent convex portion 6b.
It has such a rigidity that it does not substantially deform against the internal pressure of. A first through hole 11 having a predetermined diameter is formed vertically through the sealing lid 6 at a substantially central position, and the first through hole 11 is sealed by an elastic film 12. The elastic film 12 is adhered to the lower surface 6a, which is the surface facing the inside of the battery can 1, by means of adhesion or welding so as to surround the opening of the first through hole 11 on the inner side of the battery can 1. And then combined. The elastic film 12 is an insulating material which is not corroded by the electrolytic solution in the power generating element 3 and has elasticity, for example, natural rubber, synthetic rubber such as EPDM (ethylene-propylene-diene copolymer), polyethylene, polypropylene. And the like. The elastic film 12 is formed so as to have elasticity to be bent by receiving the internal pressure in the battery can 1 and to have a predetermined tensile breaking strength described later.

The holding member 8 is made of the above-mentioned conductive material and has a relatively large thickness. The holding member 8 is insulated from the sealing lid 6 by the insulating ring 7 interposed therebetween, and has a thickness corresponding to that of the insulating ring 7. It is disposed apart from the sealing lid 6 above. A second through hole 13 is formed vertically above the first through hole 11 and at a substantially central position of the holding member 8. The second through hole 13 has a relationship with the outer diameter of the safety valve 10 and thus the first through hole 11
The safety valve 10 has a larger predetermined inner diameter, and the safety valve 10 is inserted into the second through hole 13 from the top to the bottom of the drawing and is retained by exerting a predetermined sliding frictional force described later. In addition, in FIG. 1, 8a and 8a are gas vent holes,
3 is formed around at least one.

The positive electrode terminal 9 serves as a protective cap that protects the holding member 8 and the like, and the positive electrode 9 of the power generating element 3 is connected via the lead wire 4, the sealing lid 6, the safety valve 10, and the holding member 8. It is electrically connected to the electrode plate and serves as a plus-side terminal for extracting electric power from the sealed battery. In the figure, 9a is a gas vent hole, which is formed so as to communicate the space defined by the positive electrode terminal 9 and the holding member 8 with the outside.

The safety valve 10 has a piston-shaped main body 10a having the same cross-sectional shape corresponding to the second through hole 13 in the vertical direction and having a diameter larger than the first through hole 11 by a predetermined dimension, and a base of the main body 10a. A flange-shaped head portion 10b that is widened in the outer peripheral direction from the upper end, which is an end, is integrally formed of a predetermined conductive material, preferably a conductive material having relatively high elasticity. is there. The main body 10a
Is inserted from above into the second through hole 13 of the holding member 8, and the lower end surface 10c, which is the tip end surface thereof, projects downward from the holding member 8. Then, the main body 10a is
With the head 10b in contact with the upper surface of the holding member 8,
The lower end surface 10c covers the upper opening of the first through hole 11 of the sealing lid 6 so as to abut the upper surface 6c of the bent convex portion 6b which is a surface of the sealing lid 6 that faces the outside of the battery can 1. Is determined. That is, the vertical length of the main body portion 10a is set to be equal to or slightly larger than the total dimension of the hole length of the second through hole 13, the thickness of the insulating ring 7 in the overlapping state, and the depth of the bent convex portion 6b. Has been done. As a result, at the time of assembly, the safety valve 10 is press-fitted into the second through hole 13 and the head 10b is brought into contact with the upper surface of the holding member 8, and is vertically compressed by the upper end caulking portion 1c to be in the overlapping state. Then, the elastic bending restoring force of the sealing lid 6 and the main body 1
0a and the inner peripheral surface of the second through hole 13 receive a sliding frictional resistance force, and the lower end surface 10c of the safety valve 10 and the upper surface 6c of the sealing lid 6 are in close contact with each other for electrical connection. The state (state shown in FIG. 1) is set.

The outer diameter of the main body portion 10a is a first predetermined pressure for switching to an electrically disconnected state when an internal pressure abnormality occurs.
A predetermined sliding friction resistance force is generated between the outer peripheral surface of the main body 10a and the inner peripheral surface of the second through hole 13 in relation to the set internal pressure value (for example, 10 to 15 Kg / cm2). That is, until the internal pressure in the battery can 1 reaches the first set internal pressure value, the sliding frictional resistance force against the pressing force due to the internal pressure to prevent relative movement of the safety valve 10 and maintain the electrical connection state. When the internal pressure inside the battery can 1 exceeds the first set internal pressure value, the pressing force due to the internal pressure becomes larger than the sliding frictional force, and the safety valve 10 resists the sliding frictional resistance force. Then, the sliding frictional resistance force is applied so as to move relatively to the upper side of the drawing on the outer side and switch to the electrical cut-off state (state shown in FIG. 3), with respect to the inner diameter of the second through hole 13. The outer diameter of the main body portion 10a is defined.

The tensile breaking strength of the elastic film 12 is
It is determined in relation to a second set internal pressure value (for example, about 20 Kg / cm2) set as a pressure value larger than the first set internal pressure value in order to prevent destruction of the battery can 1 itself when the above internal pressure abnormality occurs. ing. That is, when the internal pressure in the battery can 1 exceeds the first set internal pressure value and further rises to exceed the second set internal pressure value, the tensile force due to the internal pressure becomes larger than the tensile breaking strength. It is set so that the elastic film 12 is broken and the internal pressure is released (the state shown in FIG. 4).

In the sealed battery having the above structure, when the internal pressure in the battery can 1 is maintained at an appropriate internal pressure lower than the first set internal pressure value, the safety valve 10 is connected to the inner peripheral surface of the second through hole 13. The lower end surface 1 of the safety valve 10 is held in a state in which relative movement is blocked by the sliding frictional resistance force between them.
0c is kept in contact with the upper surface 6c of the sealing lid 6.
Therefore, the positive electrode plate of the power generating element 3 is maintained in an electrically connected state in which it is electrically connected to the positive electrode terminal 9 via the lead wire 4, the sealing lid 6, the safety valve 10, and the holding member 8. As a result, discharge and charge from the positive electrode terminal 9 are possible. In this state, the elastic membrane 12 may bend due to internal pressure fluctuations and adhere to the lower end surface 10c of the safety valve 10, but the inside of the battery can 1 is sealed by the sealing lid 6 and the elastic membrane 12. To be kept.

On the other hand, during charging of the sealed battery, the internal pressure in the battery can 1 rises abnormally due to overcharging and the like, and when the internal pressure exceeds the first set internal pressure value, the safety valve 10 comes into close contact with the lower end surface 10c. The pressing force acting on the lower end surface 10c of the safety valve 10 via the elastic film 12 becomes larger than the sliding frictional resistance force.
Relative to the above (see FIG. 3). As a result, the tip end surface 10c of the safety valve 10 is separated upward from the upper surface 6c of the sealing lid 6, so that the electric current from the power generating element 3 can be discharged.
The safety valve 10 is electrically disconnected from the safety valve 10. Due to this electrical interruption, the charging current is interrupted and the decomposition of the electrolytic solution in the power generation element 3 is stopped, so that it is possible to suppress further increase in the internal pressure. Moreover, since the battery is electrically cut off and does not function as a battery, the user can be made aware of the occurrence of an abnormal state and the necessity of replacing the battery.

The battery can 1 is caused by an increase in internal pressure until the above current is cut off or some abnormality.
When the internal pressure in the inside rises to the extent that it exceeds the second set internal pressure value, the elastic film 12 is broken (see FIG. 4), and the battery can 1
The gas inside is released to the outside through the first through hole 11, the gas vent holes 8a, 8a ... Of the holding member 8 and the gas vent hole 9a of the positive electrode terminal 9, thereby increasing the internal pressure in the battery can 1. The pressure is reduced to near atmospheric pressure, and damage to the sealed battery due to an abnormal rise in internal pressure is reliably prevented.

Therefore, when the internal pressure rises abnormally, the current is first shut off by the main body portion 10a of the piston-like safety valve 10 and the second portion.
This is performed by the current cutoff mechanism constituted by the separation of the safety valve 10 and the sealing lid 6 based on the setting of the sliding friction resistance force with the through hole 13, and then the release of the internal gas is performed in the first through hole 1
A two-step fail-safe operation is performed, which is performed by an internal pressure release mechanism configured by breaking the elastic film 12 based on the tensile breaking strength of the elastic film 12 that seals the first member.

In such a sealed battery safety device, when the internal pressure is in an appropriate state lower than the first set internal pressure value,
Holding member 8 holding the safety valve 10 via the insulating ring 7
Since the sealing lid 6 and the sealing lid 6 are superposed and swaged by the swaging portion 1c, the lower end surface 10c of the safety valve 10 and the upper surface 6c of the sealing lid 6 are kept in contact with each other. For this reason,
Even if shock or vibration is applied to the battery can 1, the contact between the safety valve 10 and the sealing lid 6 can be reliably maintained. Therefore, even if the lower end surface 10c of the safety valve 10 and the sealing lid 6 are not welded, the above-mentioned electrical connection state is more reliably maintained, and the reliability of the product during normal use is further improved. . That is, unlike the conventional case, it is not necessary to perform welding for maintaining the electrical connection state during normal use, and the predetermined avoidance operation does not become uncertain due to the welding. Moreover, since it is not necessary to perform such delicate welding at the time of assembling, the process control in the production line can be facilitated and the reliability of the product can be improved. Furthermore, since the electrical connection between the safety valve 10 and the sealing lid 6 can be made by abutting instead of welding, there is no restriction that the connecting surface of the electrical connection in the case of welding must be extremely small. From the lower end surface 10c of the safety valve 10 to the first through hole 11
The relatively wide donut-shaped connecting surface excluding the cross-sectional area allows electrical connection and stable current flow.

Further, since the sealing lid 6 has such rigidity that it does not deform even if it receives the above-mentioned internal pressure, the internal pressure directly and effectively acts on the lower end surface 10c of the piston-like safety valve 10 and the relative movement of the safety valve 10 is performed. The electrical connection with the sealing lid 6 can be released directly by itself. For this reason, when an internal pressure rise exceeding the first set internal pressure value occurs, compared to the case where the internal pressure is indirectly applied to the entire conventional disc-shaped explosion-proof valve, the electrical cutoff state is maintained. Switching can be performed with high responsiveness to changes in internal pressure.

Moreover, switching between electrical connection and disconnection is
Since the sliding frictional resistance is set mainly by setting the outer diameter of the safety valve 10 with respect to the inner diameter of the second through hole 13, compared to the case of setting the tensile rupture strength of the welded portion as in the conventional sealed battery, It is possible to easily make settings and change settings. For this reason, it is possible to set a value that surely corresponds to the above-mentioned first set internal pressure value, and to make the switching timing from the electrically connected state to the disconnected state reliable according to the internal pressure in the battery can 1. be able to. At this time, by forming the safety valve 10 from an elastic material, the sliding frictional resistance force can be more reliably exhibited, and the sliding frictional resistance force to be exerted can be set more easily.

Moreover, even when the safety valve 10 is relatively moved upward and brought into an electrically cutoff state, the safety valve 10 is held at that position by the sliding friction resistance force between the safety valve 10 and the second through hole 13. Even when the internal pressure is released, there is no reversion, and it is possible to reliably maintain the electrical cutoff state and make the user aware of the abnormal state.

<Second Embodiment> FIG. 5 shows a safety device for a sealed battery according to a second embodiment of the present invention. The second embodiment is based on the structure of the first embodiment and has a structure in which the sealing body 2 is configured by adding a mechanism for interrupting a current due to an increase in internal temperature.

That is, in FIG. 5, 14 is a PTC thermistor (Positive Tempe) formed in a donut plate shape.
rature Coefficient Thermistor; Positive Characteristic Thermistor)
The PTC thermistor 14 is interposed between the holding member 8 and the positive electrode terminal 9, and the holding member 8 and the positive electrode terminal 9 are connected to each other only via the PTC thermistor 14. There is. The PTC thermistor 14 may be installed at any position on the electric conduction path between the power generation element 3 and the positive electrode terminal 9.

The PTC thermistor 14 is a thermistor having a positive temperature coefficient in which the resistance value increases as the temperature rises. In particular, the PTC thermistor 14 has a resistance value that rapidly increases in a predetermined set temperature range (for example, 100 ° C. range). It is configured to have increased switching characteristics. That is, in the PTC thermistor 14, the resistance value of the PTC thermistor 14 is extremely low in the normal temperature range up to the set temperature range. Therefore, a current flows between the holding member 8 and the positive electrode terminal 9 via the PTC thermistor 14. While flowing well, the resistance value of the PTC thermistor 14 suddenly increases in a high temperature range exceeding the set temperature range, so that the energization between the holding member 8 and the positive electrode terminal 9 is substantially cut off. Has become.

Since the other structure of the second embodiment is the same as that of the first embodiment, the same constituent members are designated by the same reference numerals and the detailed description thereof will be omitted.

In the case of the second embodiment having such a structure, if the internal temperature in the battery can 1 is within the normal temperature range up to the above set temperature range, the positive electrode plate of the power generating element 3 to the lead wire 4,
The current path to the positive electrode terminal 9 is electrically connected via the sealing lid 6, the safety valve 10, the holding member 8, and the PTC thermistor 14, and the positive electrode terminal 9 can be discharged and charged. On the other hand, if the internal temperature of the battery can 1 exceeds the set temperature range due to heat generation in the battery can 1 due to the occurrence of overcharge or a short circuit, the PTC thermistor 14 blocks the current flow and the current path is electrically connected. It will be in a state of shutting off. In particular, when the short circuit occurs, an excessive current flows in the path and the internal temperature rises rapidly, so that the PTC thermistor 14 immediately shuts off the excessive current flow between the power generating element 3 and the positive electrode terminal 9. be able to.

Therefore, the electrical connection between the lower end surface 10c of the safety valve 10 and the sealing lid 6 is separated by the relative movement of the safety valve 10 so as to have a function of interrupting the current based on an increase in the internal pressure and a function of releasing the internal pressure by breaking the elastic film 12. In addition, the current interruption function based on the internal temperature rise as described above can be added as a safety device.

<Third Embodiment> FIG. 6 shows a safety device for a sealed battery according to a third embodiment of the present invention. In the third embodiment,
The sealing body 2 as a whole is pre-integrated based on the structure of the second embodiment.

That is, in the third embodiment, the positive electrode terminal 9
And the PTC thermistor 14 and the holding member 8 holding the safety valve 10 in the second through hole 13 are overlapped with each other, and the upper and lower surfaces and the outer peripheral surfaces of the outer peripheral portions of these three members 9, 14, 8 are cross-sectionally cross-sectioned. While being covered by a letter-shaped insulating ring 7 ', a sealing lid 6'on which the elastic film 12 is attached from the lower side is superposed on the above-mentioned three members 9, 14, 8 and extended from the outer peripheral portion of the sealing lid 6'. The sealing body 2 is wrapped and sandwiched by the portion 6d.
Are previously integrated as one component. Then, the integrated sealing body 2 is fitted into the opening 1a of the battery can 1 through the insulating gasket 5, and is caulked and fixed by the caulking portion 1c.

Since the other construction of the third embodiment is the same as that of the second embodiment, the same components are designated by the same reference numerals and detailed description thereof will be omitted.

In the case of the third embodiment, the assembling work to the opening 1a of the battery can 1 is performed only by assembling the above-mentioned integrated sealing body 2, and the assembling work can be made efficient. Moreover, since the sealing body 2 can be independently assembled in advance, a test for confirming the operating state of the safety valve 10 can be performed before the sealing body 2 is assembled to the battery can 1.

In the third embodiment, the one having the PTC thermistor 14 is shown and described, but the present invention is not limited to this, and the structure of the first embodiment in which the PTC thermistor 14 is not provided is the same as that of the third embodiment. The invention may be applied. In addition, this integration may be performed by extending the outer peripheral portion of the positive electrode terminal 9 so as to sandwich up to the lower side of the sealing lid 6, and by using a separate sandwiching member, both outsides of the sealing lid 6 and the positive electrode terminal 9 may be sandwiched. You may make it clamp a peripheral part.

<Fourth Embodiment> FIG. 7 shows a safety device for a sealed battery according to a fourth embodiment of the present invention. In this fourth embodiment,
While using the structure of the first embodiment as a basis, a sealing lid 15 having a structure different from that of the first embodiment is used.

The sealing lid 15 is, as shown in FIG.
The pair of lid members 16 and 17 formed of the same conductive material as the sealing lid 6 in the first embodiment and the upper and lower surfaces are closely attached to each other by being sandwiched between the pair of lid members 16 and 17. The elastic film 18 is included. In the pair of lid members 16 and 17, bending convex portions 16a and 17a are formed at the central side portions,
First through-holes 11, 11 penetrating vertically in the approximate center position
Are formed. Then, the pair of lid members 16,
Reference numeral 17 is crimped and fixed by caulking at the outer peripheral edge portion with the elastic film 18 which is spread over substantially the entire range between the facing surfaces, and the lead wire 4 is connected through the caulking fixing portion. The lower surface 16b of the first lid member 16 is electrically connected to the upper surface 17b of the second lid member 17 with which the lower end surface 10c of the safety valve 10 abuts. The elastic film 18
May be simply interposed or may be interposed with an adhesive. The elastic film 18 is the elastic film 1 in the first embodiment.
It is formed of an insulating material having elasticity similar to that of No. 2 and has a tensile rupture strength such that it breaks when receiving an internal pressure exceeding the second set internal pressure value described in the first embodiment.

Since the other structure of the fourth embodiment is the same as that of the first embodiment, the same components are designated by the same reference numerals and the detailed description thereof will be omitted.

In the case of the fourth embodiment, when the internal pressure in the battery can 1 is within the range of normal use up to the first set internal pressure value, the power generating element 3 and the positive electrode terminal 9 have both the lead wire 4 and the sealing lid 15. While being electrically connected via the lid members 16 and 17, the safety valve 10 and the holding member 8, the elastic film 18 blocks between the first through holes 11 and 11 of the lid members 16 and 17, respectively. The inside of the battery can 1 is sealed by the sealing lid 15 (see FIG. 7).

When the internal pressure rises and exceeds the first set internal pressure value, the safety valve 10 moves upward relative to the second through hole 13 as a result, as shown in FIG. Is separated from the upper surface 17b of the sealing lid 15 upward, whereby the electric current from the power generating element 3 is cut off between the sealing lid 15 and the safety valve 10 to be in an electrical cutoff state.

When the internal pressure rises and the internal pressure exceeds the second set internal pressure value, the elastic film 18 is broken at the first through hole 11 under the internal pressure as shown in FIG. , The gas inside is discharged to the outside through both the first through holes 11 and 11 and the gas vent holes 8a, 8a and 9a, whereby the internal pressure becomes close to the atmospheric pressure, and the internal pressure is released.

In the fourth embodiment as described above, the elastic film 18 itself is connected to the sealing lid 15 in a wide area having substantially the same extent as the sealing lid 15, so that the first through hole in the case of the first embodiment is formed. Compared with the case where it is connected only around 11,
The tightness of the first through hole 11 becomes more reliable, and the connecting work for the tightness becomes easier. Moreover, by forming the sealing lid 15, it is possible to obtain a state in which the first through hole 11 is reliably sealed, and after forming the sealing lid 6 as in the first embodiment, the elastic film 12 is bonded to a predetermined position. Compared with the case of connecting by means such as etc., it is possible to save labor and ensure the manufacturing thereof. Further, of the elastic film 18, only the part facing the first through hole 11 can be surely made into a free state, and when the internal pressure exceeding the second set internal pressure value is received, the elastic film 18 of the part is removed. It can be reliably broken. Further, as in the first embodiment, the elastic film 12 is formed on the lower surface 6a of the sealing lid 6.
Since there is no need to bond the lead wires to each other, there is no space limitation when connecting the lead wires 4, and the work of connecting the lead wires 4 can be facilitated and ensured.

<Other Embodiments> The present invention is not limited to the above-described first to fourth embodiments, but includes various other modifications. That is, in each of the above-mentioned embodiments, the head 10b is formed as the safety valve 10, but the present invention is not limited to this, and the head 10b is omitted and the main body 1 is omitted.
The safety valve may be configured only by 0a. That is, the head 10b has an essential role in positioning the safety valve when it is assembled to the holding member 8, and is not related to the operation of the safety valve when the internal pressure is abnormal.

In each of the above-described embodiments, the holding member 8 has a disk shape, but the holding member 8 is not limited to this and may have a band plate shape, for example. In this case, even if the gas vent hole 8a is not provided, the elastic films 12 and 18 are broken, so that the gas can be vented through the first through hole 11 and the gas vent hole 9a.

In each of the above-mentioned embodiments, the sealing lids 6 and 15 have the bent convex portions 6b, 16a and 17a in the central portion, but the sealing lids 6 and 15 are not limited to these and may be flat.

In each of the above-described embodiments, the elastic films 12, 18 and the lower end surface 10c of the safety valve 10 in the first through hole 11 are in a non-adhered state. However, the present invention is not limited to this.
As shown in FIG. 1, the elastic films 12 and 18 (only the elastic film 12 is shown in FIG. 11) may be previously bonded to the lower end surface 10c within the range of the first through hole 11. Even in this case, the elastic films 12 and 18 extend at the hole edge portion of the first through hole 11 due to the increase in the internal pressure, and receive the internal pressure exceeding the second set internal pressure value and break at the hole edge portion. And by doing in this way, when internal pressure rises, the internal pressure can act more directly on the safety valve 10.

Further, the PTC thermistor 14 in the second embodiment is interposed, and the current interruption mechanism associated with the rise in the internal temperature and the sealing body 2 in the third embodiment are integrated in advance to save the labor of assembling work. Also, a technique that enables an operation test before assembling may be applied to the fourth embodiment.

Further, in the fourth embodiment, the sealing lid 15 is integrally formed by caulking and fixing the outer peripheral portions of the pair of lid members 16 and 17, but the invention is not limited to this. A plurality of rivets 19 in which members are arranged at equal intervals in the circumferential direction around the first through hole (see the alternate long and short dash line in FIG. 7).
The sealing lid 15 may be configured by pressure bonding with each other. In this case, the electrical connection between the lead wire 4 and the safety valve 10 via the sealing lid 15 is more reliably performed via the rivet 19.

[0074]

As described above, according to the safety device for a sealed battery in the invention described in claim 1, the sealing body is a sealing lid having rigidity and the first through hole is sealed with an elastic film,
A safety valve whose front end face is brought into contact with the sealing lid and faces the first through hole of the sealing lid, and the safety valve is stacked in an insulating state with the sealing lid, and the safety valve is fitted in the second through hole to have a sliding friction resistance force. Since it is composed of a holding member that holds the safety valve, the electrical connection state during normal use can be maintained even if the tip surface of the safety valve and the sealing lid are not welded, and the electrical connection state is maintained. It can be held securely. That is, unlike the conventional case, it is not necessary to perform welding for maintaining the electrical connection state during normal use, and the predetermined avoidance operation does not become uncertain due to the welding. When the internal pressure inside the battery can exceeds the set internal pressure value due to overcharging or the like, the internal pressure is directly applied to the tip surface of the safety valve via the elastic membrane, and the relative movement of the safety valve causes the safety valve and the sealing lid to move. The pressing force can be concentratedly applied to the side where the electrical connection is released due to the contact of the contact point (2), and when the internal pressure rises, it can be switched to the electrical cutoff state with good responsiveness. This allows the user of the battery to quickly recognize the occurrence of the abnormality.

Moreover, switching between electrical connection and disconnection in accordance with the internal pressure inside the battery can can be performed by setting the sliding frictional resistance force between the safety valve and the second through hole. Compared with the case of setting the breaking strength of the welded part, the setting and change of the setting can be performed easily and surely, and the process control at the time of assembly can be facilitated, and the reliability of the product can be improved. .

In addition, even when the safety valve relatively moves upward and is electrically cut off, the safety valve is held at that position by the sliding frictional resistance between the safety valve and the second through hole. It is possible to prevent the reversal of the electric field, and to surely maintain the electrical cutoff state so that the user can recognize the abnormal state.

According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the central portion of the sealing lid is formed so as to be convex toward the inside of the battery can.
The bending increases the cross-sectional rigidity of the sealing lid,
Even if it is thin, it can be made so as not to be substantially deformed against the internal pressure in the battery can.

According to the invention of claim 3, in addition to the effect of the invention of claim 1, the second set internal pressure larger than the first set internal pressure value for relatively moving the safety valve as the tensile rupture strength of the elastic membrane. Since it is set to break when it receives an internal pressure that exceeds the internal pressure, the internal pressure in the battery can rises and exceeds the first set internal pressure value, so that the electrical disconnection state can be achieved first. Rises and exceeds the second set internal pressure value, the internal pressure can be released by breaking the elastic membrane. Therefore, when the internal pressure of the battery can is abnormal, the current is first interrupted to let the user of the battery recognize the occurrence of the abnormality, and even if the user leaves it,
By releasing the internal pressure by venting the gas inside, it is possible to realize a two-step safe operation in which a further increase in the internal pressure can be avoided and destruction of the sealed battery can be avoided.

According to the invention described in claim 4, in addition to the effect according to the invention described in claim 3, the holding member is formed in a disk shape so as to shield the opening of the battery can, and the gas penetrating in the inward and outward directions. Since the hole is provided, even if the shape of the holding member is to be coupled to the inner peripheral portion of the opening of the battery can at the outer peripheral edge portion like the sealing lid, the elastic membrane ruptures the above The gas inside the battery can can be discharged through the gas vent hole.

According to the invention of claim 5, in addition to the effect of the invention of claim 1 or 3, the elastic film is attached to the surface of the sealing lid facing the inside of the battery can, and the first through hole is formed. Since it is arranged so as to seal the opening on the side facing the inside of the battery can, the sealing of the inside of the battery can by the sealing lid and the loading of the internal pressure through the first through hole to the tip surface of the safety valve are performed. It can be performed with the tip surface of the safety valve in contact with the sealing lid.

According to the sixth aspect of the invention, in addition to the effect of the first or third aspect of the invention, the sealing lid is composed of a pair of lid members which are polymerized with each other, and the elastic film is formed by the pair of lid members. The first lid member and the second lid member of the above-mentioned pair of lid members are sandwiched between the facing surfaces of the lid members and closely contact with each lid member.
Since the through hole is hermetically sealed, as in the case of claim 5, the inner surface of the battery can is hermetically sealed and the inner surface of the safety valve is loaded with the internal pressure through the first through hole. It can be performed in the state of being in contact with. Moreover,
The elastic membrane and the sealing lid can be fixed in position relative to each other, and particularly when the elastic membrane is broken as in the invention of claim 3, it is possible to more reliably break it with a predetermined tensile breaking strength. it can. Furthermore, since the elastic film is not provided on the surface facing the inside of the battery can, the restrictions on the space for connecting the lead wires should be eliminated to facilitate and ensure the work of connecting the lead wires. You can

According to the seventh aspect of the invention, in addition to the effect of the first aspect of the invention, since the elastic membrane is bonded in close contact with the tip surface of the safety valve, the internal pressure inside the battery can is increased. When the internal pressure rises, the internal pressure can be directly applied to the tip surface of the safety valve, and the switching to the electrical cutoff state due to the increase in the internal pressure can be performed with higher responsiveness.

According to the invention of claim 8, in addition to the effect of the invention of claim 1, a safety valve is provided with a columnar main body fitted in the second through hole, and a base end of the main body. Since it is composed of a head portion that is formed on the side and contacts the outer surface of the holding member, the safety valve is held by the head portion in the normal use state where the tip surface of the safety valve is held in contact with the sealing lid. While increasing the electrical connection area with the member, even after the relative pressure of the safety valve relative to the internal pressure of the battery can rises and exceeds the set internal pressure value, the outer peripheral surface of the main body at the position after the movement. The safety valve can be held without falling off from the holding member by the sliding frictional resistance between the second through hole and the second through hole.

According to the invention described in claim 9, in addition to the effect of the invention described in claim 1, in the middle of the current path between the lead wire and the sealing body, the resistance value in the set temperature range is increased. Since the PTC thermistor that increases rapidly is interposed, while the internal temperature of the battery can is at an appropriate temperature lower than the set temperature, the current can be properly passed through the current path, while the internal temperature is short-circuited. When the temperature rises above the set temperature range due to the occurrence of the above, etc., the resistance value of the PTC thermistor can be rapidly increased in response to the increase to substantially interrupt the current flow through the current path, and the internal temperature abnormal By adding a safety operation at the time, it is possible to further improve safety.

Further, according to the invention of claim 10,
In addition to the effect of the invention according to claim 1, as a sealing body, a positive electrode terminal, a holding member in a state where a safety valve is fitted and held in the second through hole, an insulating member, and a tip surface of the safety valve. Since the outer edge portions of the sealing lid and the sealing lid in contact with each other are preliminarily combined and integrated with each other in a state of being overlapped with each other, the assembling work to the opening portion of the battery can is facilitated. Moreover, a test for confirming the operation of the safety valve can be performed separately from the battery can before the assembling.

[Brief description of drawings]

FIG. 1 is a top sectional view showing a first embodiment of the present invention.

FIG. 2 is an exploded perspective view in which a part of the sealing body is omitted.

FIG. 3 is a view corresponding to FIG. 1 showing an electrical cutoff state.

FIG. 4 is a view corresponding to FIG. 1 showing an internal pressure released state.

FIG. 5 is a view, corresponding to FIG. 1, showing a second embodiment.

FIG. 6 is a view corresponding to FIG. 1 showing a third embodiment.

FIG. 7 is a view corresponding to FIG. 1 showing a fourth embodiment.

FIG. 8 is an exploded perspective view of a sealing lid according to a fourth embodiment.

FIG. 9 is a diagram showing an electrical cutoff state in the fourth embodiment.
FIG.

FIG. 10 is a view showing a state where internal pressure is released in the fourth embodiment.
FIG.

FIG. 11 is a view corresponding to FIG. 1 showing another example of the mode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery can 2 Sealing body 3 Power generation element 4 Lead wire 6,6 ', 15 Sealing lid 7,7' Insulating ring (insulating member) 8 Holding member 8a Gas vent hole 9 Positive electrode 10 Safety valve 10a Main body 10b Head 10c Lower End face (front end face) 11 First through hole 12,18 Elastic film 13 Second through hole 14 PTC thermistor 16,17 Lid member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Ouchi 8 Nishinomachi, Higashimukaijima, Amagasaki City, Hyogo Prefecture Mitsubishi Electric Wire & Cable Co., Ltd.

Claims (10)

[Claims] 1. A safety device for a sealed battery, wherein a power generating element is housed inside a battery can and provided in a sealing body that seals an opening of the battery can, wherein the sealing body faces the inside of the battery can and opens. First to do
While having a through hole, the lead wire from the power generating element is connected to the surface facing the inside of the battery can, while the outer peripheral edge is airtightly attached to the opening of the battery can to counter the internal pressure of the battery can. A sealing lid made of a conductive material that has a rigidity that does not substantially deform, an insulating elastic film that closes the first through hole of the sealing lid to seal the inside of the battery can, and the internal pressure of the battery can. A piston-shaped safety valve made of a conductive material that moves relative to each other when lifted up, and a second through hole that holds the safety valve in an internally fitted state. The outer edge portion is the opening of the battery can and is located outside the sealing lid. Is provided with a holding member made of a conductive material that is fixed in position in a state of being polymerized via an insulating member and a surface of the sealing lid facing the outside of the battery can, and the safety valve is formed from a first through hole of the sealing lid. It has a large tip surface, and the tip surface is the first through hole. Is arranged so as to be in contact with the surface of the sealing lid facing the outside of the battery can in an electrically connected state, and the outer peripheral surface of the safety valve and the inner peripheral surface of the second through hole are the battery. Until the internal pressure of the can rises and reaches the set internal pressure value, it resists the internal pressure and keeps the relative movement of the safety valve with respect to the sealing lid, while holding the safety valve by the action of the internal pressure exceeding the set internal pressure value. A safety device for a sealed battery, wherein the safety devices are tightly fitted to each other so as to exert a sliding frictional resistance force so as to move relatively to the side away from the sealing lid. 2. The safety device for a sealed battery according to claim 1, wherein the sealing lid is bent and formed so that a central portion thereof is convex inward of the battery can. 3. The battery according to claim 1, wherein the elastic membrane receives a battery can internal pressure exceeding a second set internal pressure value set as a pressure value larger than a set internal pressure value for relatively moving the safety valve to the side away from the sealing lid. A sealed battery safety device characterized in that its tensile breaking strength is set so as to break. 4. The sealed battery according to claim 3, wherein the holding member is formed in a disk shape so as to shield the opening of the battery can, and has a gas vent hole penetrating inward and outward. Safety device. 5. The elastic film according to claim 1 or 3, wherein the elastic film is attached to a surface of the sealing lid facing the inside of the battery can so as to seal the opening of the first through hole on the side facing the inside of the battery can. A safety device for a sealed battery, which is characterized by being arranged. 6. The sealing lid according to claim 1 or 3, wherein the sealing lid comprises a pair of lid members each having a first through hole at the same position and being overlapped with each other in the inward and outward directions, and the elastic film includes the pair of lid members. A sealed battery, characterized in that it is sandwiched between the facing surfaces of the pair of lid members in a state in which both the first through-holes of the lid member are blocked and widened, and they are in close contact with each other and connected to a sealing lid. Safety device. 7. The safety device for a sealed battery according to claim 1, wherein the elastic film is bonded in a state of being in close contact with the tip surface of the safety valve. 8. The columnar main body according to claim 1, wherein the safety valve has the same cross-sectional shape from the base end to the tip and corresponds to the second through hole of the holding member, and is arranged so as to project from the inner surface of the holding member to the sealing lid side. A safety device for a sealed battery, characterized in that it is composed of a portion and a head portion that spreads from the base end side of the main body portion to contact the outer surface of the holding member. 9. The sealed battery according to claim 1, wherein a PTC thermistor whose resistance value rapidly increases in a set temperature range is provided in the middle of the current path between the lead wire and the sealing body. Safety device. 10. The sealing body according to claim 1, further comprising a positive electrode terminal which is provided at an opening of the battery can outside the holding member and electrically connected to the holding member. A holding member with the safety valve fitted, an insulating member, and a sealing lid with the end face of the safety valve in contact with each other, which are preliminarily combined and integrated with each other at their outer edges. A safety device for a sealed battery, which is characterized in that