JP2002075316A - Sealed lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery excellent in durability by making a proper oil material used by painting on a rubber valve, in a battery equipped with a safety valve having a structure with an exhaust vent sealed by the rubber valve. SOLUTION: EPDM rubber is used for the material of the rubber valve, and perfluoropolyether oil composed of only carbon containing no chlorine in its molecular structure, fluorine and oxygen is painted on it, in the structure of this sealed lead-acid battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed lead-acid battery, and more particularly to an improvement in a safety valve for the battery.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a conventional safety valve structure for a sealed lead-acid battery. This structure is a structure in which the end of a pipe-shaped exhaust port 2 provided in a battery case cover 1 is covered with a cap-type rubber valve 3 to maintain airtightness. And a safety valve with such a structure
When the pressure inside the battery rises due to the gas generated inside the lead-acid battery, the cap-type rubber valve opens to prevent the battery case made of synthetic resin from cracking, and the gas is discharged from the exhaust port.
Further, when the pressure in the battery is reduced, for example, when the battery is left unattended, the cap-type rubber valve is in close contact with the pipe-shaped exhaust port and operates to prevent external air from entering the lead-acid battery.

In a sealed lead-acid battery having a safety valve having a structure in which the exhaust port is sealed with a rubber valve, chloroprene rubber, EPDM rubber, and the like have been used as the material of the rubber valve. From the point of EP recently
The use of DM rubber is increasing.

In addition, the airtightness of the safety valve is improved,
In order to prevent deterioration of the rubber valve, silicone oil or fluorine oil is applied to the rubber valve as a sealing oil.

[0005]

The silicone oil that has been conventionally applied to a rubber valve has the characteristics that the vapor pressure is relatively high and the oil evaporates over a long period of use.
For this reason, in a battery having a structure in which silicone oil is applied to a rubber valve, the rubber valve deteriorates early, the safety valve does not operate at a predetermined pressure, the internal pressure increases, and the battery case is swollen or cracked. There was a problem.

On the other hand, when fluorine oil is used, if it is applied to a rubber valve made of chloroprene rubber, there is a problem that the components in the rubber are eluted into the oil and the deterioration of the rubber valve is accelerated. However, when fluorine oil is mixed into the battery, there is a problem that the self-discharge speed of the battery is increased depending on the type of the fluorine oil.

An object of the present invention is to solve the above problems and provide a battery having excellent durability.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a sealed lead-acid battery having a safety valve having a structure in which an exhaust port is sealed with a rubber valve, wherein the rubber valve is made of fluorine oil containing no chlorine in its molecular structure. It is characterized by being applied.

According to the present invention, as a result of various studies on oil applied to a rubber valve, fluorine oil has a relatively low vapor pressure. Further, the above-mentioned problems caused when fluorine oil is used are contained in the molecules of fluorine oil. It was done by finding out what chlorine was causing it. Then, by applying a fluorine oil containing no chlorine in the molecular structure to the rubber valve, the above-mentioned problem is solved and a battery having excellent durability can be realized.

[0010] As the fluorine oil containing no chlorine in the molecule, a perfluoropolyether oil consisting of only carbon, fluorine and oxygen is particularly preferable. this is,
Such a fluorine oil is cheaper than, for example, a fluorine oil consisting only of carbon and fluorine, and has chemical resistance,
This is because it has excellent performance such as compatibility with a rubber valve and a battery case resin.

As a material of the rubber valve to which the fluorine oil containing no chlorine in the molecule is applied, EPDM rubber is particularly preferable, and a perfluoropolyether-based oil composed of only carbon, fluorine, and oxygen is added to EPDM rubber. Is more preferable. This is because the reactivity between the rubber and the fluorine oil can be further suppressed, and the durability can be further increased.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below together with examples.

The sealed lead-acid battery of the present invention is a sealed lead-acid battery having a safety valve having a structure in which an exhaust port is sealed with a rubber valve. As the safety valve structure, for example, the structure shown in FIG. As a matter of course, the size of the rubber valve varies depending on the size of the pipe-shaped exhaust port.

The following is an example in which the present invention is applied to a sealed lead-acid battery of 2 V, 200 Ah.

The structure of the safety valve is the same as that shown in FIG. The material of the cap type rubber valve 3 is EPDM rubber, and the inner diameter thereof is slightly smaller than the outer diameter of the pipe-shaped exhaust port 2. The shear hardness of the EPDM rubber used was 45, the dimensions of the cap type rubber valve 3 were 11.5 mm in diameter, and the side wall thickness was 1.
The dimensions of the pipe-shaped exhaust port 2 are 0 mm, the top wall thickness is 1.8 mm, the height is 6.0 mm, and the diameter is 12 mm and the height is 10 mm. As the sealing oil (oil applied to the rubber valve), a perfluoropolyether-based oil shown in Table 1 below (a table showing the molecular formula of the applied oil) was used. For comparison, batteries using silicon oil and fluorine oil (containing chlorine) instead of the perfluoropolyether-based oil were produced.

[0016]

[Table 1] These three batteries were subjected to a float test at 60 ° C. and 2.23 V / cell for one year, and a capacity test was conducted every two months. After the float test, the on-off valve pressure of the safety valve was measured to determine whether or not the valve operates normally. FIG. 2 shows the change in capacity during the float test.

In the battery coated with silicone oil, the safety valve did not operate normally, and the discharge capacity was low even in the float test. This is because the oil evaporates with the passage of the test period, the rubber valve does not operate normally, the airtightness is lost, and external air enters the battery.

In the battery coated with fluorine oil (containing chlorine), the discharge capacity was reduced at an early stage, but the rubber valve operated normally. This was because the fluorine oil (chlorine-containing) applied to the rubber valve entered the battery, which adversely affected battery performance.

On the other hand, the battery coated with the perfluoropolyether-based oil operates normally even after one year of the float test, and has a discharge capacity of about 80%. It was found that the oil had a small capacity reduction and was an excellent oil.

FIG. 3 shows the vapor pressures of the various oils used above. It can be seen that the perfluoropolyether-based oil has a lower vapor pressure than other oils and is less likely to evaporate.

FIG. 4 shows the effect on the battery performance when the various oils used are mixed in the electrolyte. This figure is a diagram showing the transition of terminal voltage when a 2 V, 50 Ah sealed lead battery was added with 2 wt% of various oils shown in Table 1 and subjected to a standing test at 60 ° C. Was regarded as the self-discharge rate.

The terminal voltage of silicon oil and perfluoropolyether-based oil was 2 V or more even after 40 days, whereas fluorine oil (containing chlorine) was 1.5% on day 10.
V or less. This was because chlorine in the molecular structure was liberated from the oil and increased the self-discharge rate.

Table 2 below summarizes the test results for batteries using the above-mentioned various oils.

[0024]

[Table 2] From the above results, it was found that the battery of the example of the present invention using the perfluoropolyether-based oil had an excellent operating state of the safety valve, and did not cause deterioration of battery characteristics due to mixing of oil into the battery.

In the above embodiment, a perfluoropolyether-based oil having a structure having a side chain was used. However, the present invention is not limited to this.
When a perfluoropolyether-based oil composed only of oxygen is used, the same effect as that obtained in the battery of the above embodiment can be obtained.

[0026]

According to the sealed lead-acid battery of the present invention in which the rubber valve is coated with fluorine oil containing no chlorine in the molecular structure, a battery having excellent durability can be obtained. In particular, by using a rubber valve in which perfluoropolyether-based oil is applied to EPDM rubber, the adverse effect of the oil on battery performance is greatly reduced, and the operating pressure of the on-off valve is almost the same as the initial state even during long-term use. Can be maintained in a stable manner.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a safety valve structure for a sealed lead-acid battery.

FIG. 2 is a diagram showing a change in capacity during a 60 ° C. float test.

FIG. 3 is a diagram showing vapor pressures of various oils.

FIG. 4 is a diagram showing a transition of terminal voltage when a standing test is performed at 60 ° C.

[Explanation of symbols]

 1. Battery case lid 2. 2. Pipe-shaped exhaust port Cap type rubber valve 4. Terminal

Claims (3)

[Claims] 1. A sealed lead-acid battery having a safety valve having a structure in which an exhaust port is sealed with a rubber valve, wherein the rubber valve is coated with fluorine oil containing no chlorine in a molecular structure. Sealed lead-acid battery. 2. The sealed lead-acid battery according to claim 1, wherein said fluorine oil is a perfluoropolyether-based oil comprising only carbon, fluorine and oxygen. 3. The sealed lead battery according to claim 1, wherein the material of the rubber valve is EPDM rubber.