JPH09134714A - Coned disc spring for safety device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spring for safety device, with which two types of safety devices can be used complexly without causing complication of the structure. SOLUTION: The current feeding path for a safety device 12 follows a route consisting of a power generating element 13, lead 30, terminal 29 of conductor case 17, spacer 19, PTC plate 21, ring-shaped terminal 22, contact piece 25, and electrode lid 26. When an over-current flows, the PTC plate 21 emits heat and its resistance becomes very large so that the over-current is suppressed. If nevertheless gas is generated from the element 13 and the internal pressure of a battery case 14 rises, a coned disc spring 1 is inverted so that the tip of the contact piece 25 is heaved to cause separation from the terminal 22, and the current feeding path is shut. If the internal pressure of the case 14 continues still rising, a plastic film and aluminum foil at a hole in the disc spring 1 are broken, and the gas is released to the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc spring for a safety device suitable for a safety device for preventing an explosion of a secondary battery, for example.

[0002]

2. Description of the Related Art In recent years, along with the widespread use of video cameras, headphone stereos, mobile phones, etc., there is an increasing demand for improving the heavy load characteristics of a secondary battery as a power source and increasing the energy density. As a secondary battery that satisfies this demand, a nickel-cadmium battery that has been conventionally used can be cited, but recently, a lithium battery has been attracting attention, and development and use of this lithium battery have been activated.

This type of secondary battery generally has a sealed structure. Therefore, when the power generation element generates heat due to overcharge, short circuit, etc., and gas is generated from this power generation element, the pressure in the battery case rises and the battery performance deteriorates. Furthermore, the battery case may explode, damaging surrounding equipment and damaging nearby persons.

In order to prevent such an accident, a safety device is provided in this type of secondary battery. For example, PT
A C plate (having a characteristic that the resistance sharply increases when the temperature exceeds a predetermined temperature) is inserted in the energizing path of the battery, or a switch which is switched by the pressure in the battery is inserted in the energizing path. Etc. Alternatively, there is a combination of these to increase safety, and this combination is more general.

[0005]

However, if several kinds of safety devices are combined, the safety is improved, but there is a problem that the structure is complicated and the cost is increased.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a disc spring for a safety device that enables the combination of two types of safety devices without complicating the structure.

[0007]

In order to solve the above problems, the disc spring for a safety device of the present invention has a hole, and the hole is closed by a sheet.

For example, when the disc spring is applied to a safety device for a secondary battery, the disc spring is arranged so as to be inverted by receiving the pressure in the battery, and the normally closed switch is opened by reversing the disc spring. Is inserted in the energization path of the battery.
In addition, a gas passage through which gas in the battery escapes is formed through the hole of the disc spring. In such a structure,
When gas is generated from the power generation element of the battery due to overcharge, short circuit, etc., and the pressure inside the battery rises, the disc spring reverses and the switch opens accordingly, so the power supply path of this battery is cut off. , The current is cut off. If the pressure inside the battery continues to rise despite the interruption of the current, the sheet in the hole of the disc spring is broken, and the gas inside the battery is discharged to the outside through the gas path. This reduces the pressure inside the battery and prevents the battery from exploding.

That is, since the disc spring of the present invention has two functions of switching the switch and discharging gas, the structure of the safety device can be simplified.

As a sheet for closing the hole of the disc spring, there is, for example, a metal foil. When the hole of the disc spring is closed with this metal foil, it is preferable to interpose a synthetic resin layer between the metal foil and the disc spring in order to prevent electric corrosion between the both.

A bimetal spring may be used as the disc spring. Also when applying this bimetal disc spring to a secondary battery, insert a normally-closed switch that opens by reversing the disc spring into the energizing path of the battery, and let the gas inside the battery escape through the hole of the disc spring. Create a route. In such a structure, when the power generating element of this battery generates heat due to overcharge, short circuit, etc., the heat causes the disc spring to reverse, the switch in the energizing path is opened, and the current is cut off. And, despite the interruption of this current, the power generation element of the battery continues to generate heat, and with this,
If the pressure inside the battery continues to rise, the sheet in the hole of the disc spring is broken and the gas inside the battery is discharged to the outside to prevent the battery from exploding.

[0012]

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

1 and 2 show a first disc spring of the present invention.
1 shows an embodiment. In this disc spring 1, a disc spring main body 2 made of stainless steel, a synthetic resin film 3 and an aluminum foil 4 are sequentially laminated, and a central hole 2a of the disc spring main body 2 is closed by the synthetic resin film 3 and the aluminum foil 4. Become.

The synthetic resin film 3 is interposed between the Belleville spring body 2 and the aluminum foil 4, and serves to prevent galvanic corrosion between different metals.

The synthetic resin film 3 and the aluminum foil 4 may be simply laminated, but they may be adhered. When they are adhered, the synthetic resin film 3 may be welded by a solvent or heating, Use adhesive. Further, as shown in FIG. 3, the respective synthetic resin films 5 and 6 may be laminated on both sides of the aluminum foil 4 to cover the aluminum foil 4.

Alternatively, aluminum foil may be formed on one surface of the synthetic resin film by metal vapor deposition. Also,
The aluminum foil may be vapor-deposited on one surface of the synthetic resin film, another synthetic resin film may be laminated, and the aluminum foil may be sandwiched between the two synthetic resin films.

Further, even if a synthetic resin paint or an adhesive is applied to one side of the aluminum foil and the surface of the synthetic resin paint or the adhesive is superposed on the disc spring body 2, the aluminum foil and the disc spring body are bonded together. good. Further, both sides of the aluminum foil may be coated with synthetic resin paint or adhesive.

Of course, as the material of the disc spring and the metal foil, other kinds of metal may be applied.

The material of the disc spring body 2 and the metal foil for closing the hole 2a of the disc spring body 2 are the same,
When the disc spring 1 is used in an environment where electrolytic corrosion does not occur, the synthetic resin film may be omitted and the disc spring body 2 and the metal foil may be directly laminated. Further, the aluminum foil may be omitted and only the synthetic resin film may be used.

Now, such a disc spring 1 is applied to a safety device 12 for a secondary battery 11 as shown in FIG. In this secondary battery 11, the power generation element 13 is sealed in a battery case 14, and an insulator 15 is provided on the upper end of the battery case 14.
The safety device 12 is supported by the caulking process with the intervening.

In the safety device 12, as shown in FIG. 5, a gasket 18, a disc spring 1, a spacer 19, a PTC plate 21, an annular terminal 22 and an insulating seal 23 are sequentially superposed on the inside of a conductor case 17 to form a PTC. After inserting the moving piece 24 into the holes of the plate 21 and the annular terminal 22, the contact piece 2 is placed on the moving piece 24.
5 is covered with an electrode lid 26 welded by resistance welding, the periphery of the conductor case 17 is caulked, and the periphery of the electrode lid 26 is sandwiched with an insulating seal 23 interposed.

The PTC plate 21 is a positive temperature coefficient thermistor having a characteristic that it has a low resistance at room temperature, but the resistance increases sharply when the temperature exceeds a predetermined temperature. It is provided for.

A hole 17a is formed in the bottom of the conductor case 17. The disc spring 1 has a hole 17a in the conductor case 17.
The inside of the secondary battery 11 is faced through. Further, a terminal 29 is hung on the periphery of the hole 17 a, and the terminal 29 is connected to the power generating element 13 via a lead wire 30.

The contact piece 25 of the electrode lid 26 has sufficient elasticity, and its tip is in contact with the annular terminal 22.

The energizing path of the safety device 12 is the power generating element 13 → the lead wire 30 → the terminal 29 of the conductor case 17 → the spacer 19 → the PTC plate 21 → the annular terminal 22 → the contact piece 25 → the electrode lid 26. .

In such a structure, when an overcharge or short circuit occurs and an overcurrent flows, the PTC of the energizing path is
The plate 21 generates heat, and the resistance of the PTC plate 21 becomes extremely large. As a result, the overcurrent is suppressed, the current becomes small, and the overcharge or short-circuit state is avoided.

Despite the suppression of overcurrent by the PTC plate 21, when gas is generated from the power generating element 13 and the pressure in the battery case 14 rises to exceed the allowable level, this pressure causes the phenomenon shown in FIG. The disc spring 1 is reversed like this,
The back surface of the disc spring 1 expands, and the moving piece 24 is pushed up. Along with this, the tip of the contact piece 25 is also pushed up,
This tip is separated from the annular terminal 22. As a result, the energization path is cut off and the current is cut off.

Even though the current is cut off in this way,
When the gas continues to be generated from the power generation element 13 and the pressure inside the battery case 14 continues to rise, the synthetic resin film 3 and the aluminum foil 4 of the disc spring 1 are broken as shown in FIG. The gas reaches the inside of the electrode cover 26 through the central hole 2a of the disc spring body 2 and is discharged to the outside through the hole 26a of the electrode cover 26. This prevents the battery case 14 from exploding.

That is, in the secondary battery 11,
Explosion protection of the secondary battery 11 is achieved by the triple action of suppressing the overcurrent by the PCT plate 21, cutting the energization path by reversing the disc spring 1, and releasing the internal gas by breaking the synthetic resin film 3 and the aluminum foil 4. It is carried out.

Here, two of these triple actions, that is, the action of cutting the current-carrying path and the action of releasing the internal gas are caused by the action of one disc spring 1. In other words, the Belleville spring 1 plays two roles at the same time. This allows a simplification of the structure of this safety device 12.

FIG. 8 shows another example of a safety device to which the disc spring 1 shown in FIGS. 1 and 2 is applied. This safety device 3
1 is a gasket 33, a disc spring 1, a PTC plate 34, an annular terminal 35, and an insulating seal 3 inside the conductor case 32.
6 are sequentially superposed, the peripheral edge of the contact piece 38 is sandwiched between the insulating seal 36 and the electrode lid 37, the electrode lid 37 is covered, and the peripheral edge of the conductor case 32 is caulked. The insulator 39 is sandwiched in between.

As shown in FIG. 9, the contact piece 38 of the electrode lid 37 has an annular piece 38a and a tongue piece 38b. The annular piece 38a is sandwiched between the insulating seal 36 and the electrode lid 37, The tongue piece 38b is in contact with the annular terminal 35. Further, a hole is formed in the tongue piece 38b of the contact piece 38, and the spring pusher 41 is press-fitted into this hole. This spring pusher 41 is shown in FIG.
As shown in FIG. 3, the head 41a and the two legs 41b are provided, and the gap between the legs 41b is made wider than the diameter of the hole 2a of the disc spring body 2.

This safety device 31 is also the secondary battery 1 shown in FIG.
The power supply path is applied to the power generating element 13, the lead wire 30, the terminal 42 of the conductor case 32, the PTC plate 34, the annular terminal 35, the contact piece 38, and the electrode lid 37.

When an overcharge or short circuit occurs and an overcurrent flows, the PTC plate 34 in the energizing path generates heat and its resistance becomes extremely large, and the overcharge or short circuit is avoided.

Despite the suppression of the current, if the pressure in the battery case 14 rises and exceeds the allowable level, as shown in FIG.
As shown in FIG. 1, the disc spring 1 is reversed, and the disc spring 1 pushes up each leg portion 41b of the spring pusher 41. Along with this,
The tip of the contact piece 38 separates from the annular terminal 35, and the above-mentioned energization path is cut off.

If the pressure inside the battery case 14 continues to rise despite the disconnection of the energization path, as shown in FIG. 12, the synthetic resin film 3 and the aluminum foil 4 of the disc spring 1 are formed.
And the gas in the battery case 14 is released from the central hole 2a of the disc spring body 2 to the outside through the hole 37a of the electrode lid 37, and the battery case 14 is prevented from exploding.

Therefore, also in this case, the explosion of the secondary battery 11 is prevented by the triple actions of suppressing the overcurrent, disconnecting the energizing path, and releasing the internal gas.

By the way, with this safety device 31, the operation can be inspected by the following procedure without destroying the safety device 31.

First, the electrode lid 37 and the terminal 4 of the safety device 31
Check whether there is continuity between the two. If there is no continuity, it is a defective product.

Next, pressure is applied to the disc spring 1 through the hole 32a of the conductor case 32, and the disc spring 1 is inverted. At this time, if there is still electrical connection between the electrode lid 37 and the terminal 42, it is a defective product.

Further, a thin rod (not shown) is inserted into the hole 37a of the electrode lid 37, and the contact piece 38 is formed by this thin rod.
The head 41a of the spring pusher 41 is pushed down, and the disc spring 1 is inverted again to return to the original state. Thereby, the electrode lid 3
If the 7 and the terminal 42 are electrically connected again, the safety device 31 is determined to be non-defective.

FIG. 13 shows a second embodiment of the disc spring of the present invention. This disc spring 51 has a hole 52a at the center of the disc spring main body 52 as compared with the disc spring 1 shown in FIGS.
Are identical with each other in that they are closed by the synthetic resin film 53 and the aluminum foil 54, and are different in that the disc spring main body 52 is made of bimetal.

This bimetal disc spring main body 52 has two
It has a cross-sectional structure composed of two layers 52b and 52c.
These layers 52b and 52c are layers of metals having mutually different thermal expansion coefficients, and the layer 52b on the expanded side of the Belleville spring body 52 is more thermally expanded than the layer 52c on the recessed side. The rate is small. Therefore, as the temperature of the disc spring main body 52 rises, the layer 52c on the depressed side expands more than the layer 52b on the expanded side, and the difference between the two becomes larger, and the temperature of the disc spring main body 52 increases. When you reach a predetermined level,
The disc spring body 52 is inverted.

The bimetal is not limited to two layers,
Since there are three layers, this may be applied.

This disc spring 51 is a safety device 1 shown in FIG.
2 and the safety device 31 shown in FIG. 8 can be applied instead of the disc spring 1. In this case, not only when the pressure in the battery case 14 rises due to overcharge or short circuit, but also due to the heat generated by the power generation element 13, the disc spring 5
Even when the temperature of No. 1 rises, the disc spring 51 is reversed, the energization path of the secondary battery 11 is cut, and the current is cut off.

Therefore, in the secondary battery 11 to which the disc spring 51 is applied, suppression of overcurrent by the PCT plate,
Due to the reversal of the disc spring 51 in response to the increase in pressure or the temperature, the current flow path is cut, and the synthetic resin film 53 and the aluminum foil 54 are broken to release the internal gas.
The secondary battery 11 is protected against explosion.

The disc spring of each of the above-mentioned embodiments uses the one in which the metal foil and the synthetic resin film are bonded together in order to close the hole, but the present invention is not limited to this and other disc springs may be broken. The material may be applied.
For example, application of a thin film made of synthetic resin can be considered.

[0048]

As described above, the disc spring for a safety device according to the present invention has a hole, and the hole is closed by a sheet. For example, the disc spring is applied to a safety device for a secondary battery and energized. Since the two functions of switching the switch inserted in the path and discharging gas are performed, the structure of this safety device can be simplified.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a disc spring of the present invention.

FIG. 2 is a cross-sectional view showing the disc spring of FIG.

FIG. 3 is a cross-sectional view showing a partially enlarged variation of the disc spring of FIG.

4 is a cross-sectional view showing a secondary battery including a safety device to which the disc spring of FIG. 1 is applied.

5 is a cross-sectional view showing the safety device of FIG.

FIG. 6 is a view used for explaining the operation of the safety device of FIG.

FIG. 7 is a view used for explaining another operation of the safety device of FIG.

8 is a cross-sectional view showing another safety device to which the disc spring of FIG. 1 is applied.

9 is a perspective view showing a contact piece in the safety device of FIG.

FIG. 10 is a perspective view showing spring pressing in the safety device of FIG.

FIG. 11 is a view used for explaining the operation of the safety device of FIG.

FIG. 12 is a view used for explaining another operation of the safety device in FIG.

FIG. 13 is a sectional view showing a second embodiment of the disc spring of the present invention.

[Explanation of symbols]

 1,51 Disc spring 2,52 Disc spring main body 3,53 Synthetic resin film 4,54 Aluminum foil 11 Secondary battery 12,31 Safety device 13 Power generating element 14 Battery case 15,39 Insulator 17,32 Conductor case 18,33 Gasket 19 Spacer 21,34 PTC plate 22,35 Annular terminal 23,36 Insulation seal 24 Moving piece 25,38 Contact piece 26,37 Electrode lid 29,42 Terminal 30 Lead wire 41 Spring pushing

Claims (4)

[Claims] 1. A disc spring for a safety device having a hole, the hole closing the hole with a sheet. 2. The disc spring for a safety device according to claim 1, wherein the sheet is a metal foil. 3. The disc spring for a safety device according to claim 2, wherein a synthetic resin layer is interposed between the sheet of metal foil and the disc spring. 4. The disc spring for a safety device according to claim 1, wherein the disc spring is made of bimetal in which metal layers having different thermal expansion coefficients are laminated.