JP2765325B2 - Thermal battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal battery having a built-in exothermic agent inside a battery and igniting the exothermic agent when the battery is used to heat and activate the inside of the battery to a high temperature. This facilitates checking of the battery.

[0002]

2. Description of the Related Art A thermal battery is a battery using a molten salt as an electrolyte, and is in an inactive state during storage because the electrolyte is a non-conductive solid salt. Then, by heating the inside of the battery to a high temperature, the electrolyte is melted and becomes conductive and activated.

[0003] A thermal battery is a type of storage battery that has little self-discharge during storage, can be stored for a long period of time, and can be activated instantaneously when needed. In addition, it can be used in a wide range of environmental temperatures such as -55 to 100 ° C, and is indispensable as a power source for missiles, rockets and other flying objects, and various emergency power sources.

A well-known system using calcium as a negative electrode and calcium chromate as a positive electrode as an active material of a thermal battery is known. However, lithium and lithium alloys are used as a negative electrode and a positive electrode is used as a positive electrode for higher capacity and higher output. Thermal batteries using sulfides and oxides have also been developed.

[0005] Iron, nickel, chromium, cobalt, copper,
Sulfides and oxides such as tungsten and molybdenum have high electromotive force and energy density. The positive electrode is made of a composite compound of these metals or a part of which is doped with lithium ions to improve thermal stability and discharge characteristics.

As an electrolyte, LiCl-59 mol%, KCl-4
1 mol% eutectic salt is commonly used, but KBr-LiBr
Other molten salts with high ionic conductivity, such as -LiCl-based, LiBr-KBr-LiF-based, and LiBr-LiCl-LiF-based, can be used. Is used in a state where fluidity is lost by mixing. The electrolyte layer is a conductor of ions during operation of the thermal battery, and also functions as a separator between the positive electrode and the negative electrode.

[0007] As the exothermic agent, a mixture of an oxidizing agent and a reducing agent, which generate little gas upon combustion, is used. In general,
A mixture of iron powder and potassium perchlorate is used, and a plate-shaped product is alternately laminated with a unit cell. The exothermic agent is ignited when the battery is activated, causing an oxidation-reduction reaction to generate heat, thereby heating the inside of the battery to the operating temperature. This exothermic agent contains iron in excess of the amount required for the exothermic reaction, is conductive even after the exothermic reaction,
It also acts as a connector between adjacent unit cells.

[0008]

A thermal battery can be used only once, and generates an electromotive force only by an activation operation of igniting a built-in exothermic agent. For this reason, in an inactive state, it is impossible to determine an unused product by measuring a terminal voltage like other primary batteries.

Conventionally, a proposal has been made to apply a heat-sensitive paint that changes color irreversibly depending on the temperature to a part of the surface of a thermal battery container, and to indicate activation by a change in the color. That is, if the product is not used, there is no discoloration of the heat-sensitive paint, and if it is discolored, it is determined that the product is a used product.

This method detects the temperature rise on the surface of the container of the activated thermal battery and determines whether or not the battery has been activated. Therefore, there is a drawback that the method cannot be used unless the temperature of the container surface rises. Was. When the thermal battery was used at a low temperature, or when the surface of the heat-sensitive paint was fixed in contact with a metal block or a metal band, heat from the surface escaped, so that the temperature on the surface of the container did not rise sufficiently. In addition, since the thermal battery for long-time discharge uses a thick heat-insulating layer, the temperature rise of the container is small. With the recent improvement of the heat insulation method, the temperature rise of the container tends to be further suppressed, and the temperature rise required for discoloration of the heat-sensitive paint may not be exhibited in some cases.

Furthermore, even if the thermal paint has discolored, it is necessary to observe the surface of the thermal battery to determine whether the thermal battery has been used. If the thermal battery is attached to the equipment and the thermal paint cannot be observed, the thermal battery cannot be observed. There was a drawback that it could not be determined.

As a means for detecting whether or not the thermal battery has been activated, it has been considered to measure the resistance of the ignition ball. However, the resistance value of the burned ignition ball varies depending on the combustion conditions and does not show a constant value, and the measurement of the resistance value did not determine whether the thermal battery was activated.

[0013]

According to the present invention, there is provided a thermal battery in which a unit cell and a heat generating agent are wrapped in a heat insulating material and housed in a closed container, wherein a thermal fuse which operates at an internal temperature of the activated thermal battery is incorporated. And a terminal for detecting the operation state of the thermal fuse.

[0014]

When the thermal battery of the present invention is activated, the internal temperature of the thermal battery instantaneously rises to the operating temperature due to the combustion of the built-in exothermic agent, thereby generating an electromotive force. When the temperature inside the thermal battery becomes equal to or higher than the operating temperature of the thermal fuse, the open circuit of the thermal fuse is cut off, and the thermal fuse does not conduct. The operation of the thermal fuse is irreversible, and once the thermal battery is activated, regardless of the temperature inside the thermal battery,
It becomes non-conductive. The operating state of the thermal fuse, that is, the presence or absence of conduction, can be detected from the outside via a terminal for detection. Since the thermal fuse is built in the thermal battery, it operates reliably even in a low temperature environment where the container surface temperature does not rise.

The thermal fuse operates at a predetermined fixed temperature to cut off the conduction of electric current. For example, a thermal fuse in which a low melting point metal or resin is combined with an electric contact is used.

[0016]

FIG. 1 is a sectional view of a thermal battery manufactured as an embodiment of the present invention. Reference numeral 1 denotes a unit cell, and 2 denotes a heat generating agent. 4 is a positive terminal,
Reference numeral 5 denotes a negative electrode terminal, 6 denotes an ignition ball for activating the thermal battery, and 7 denotes an ignition terminal. By supplying an ignition current to the ignition terminal 7, the thermal battery is activated and an electromotive force is generated between the positive terminal 4 and the negative terminal 5. 8 is a heat insulating material, 9
Is a container, which keeps the inside of the thermal battery warm. Reference numeral 10 denotes a thermal fuse built in the container, and reference numeral 11 denotes a terminal for detecting the operation state.

The battery of the present invention was constructed using a temperature fuse operating at 130 ° C. and activated at a low temperature of −55 ° C.
When the conduction state of the detection terminal was observed, the conduction between the detection terminals became non-conductive 12 seconds after the thermal battery was activated, and the operation of the thermal fuse was detected. The non-conducting state between the detection terminals is maintained even after the internal temperature of the thermal battery has dropped, indicating that the thermal battery has already been activated.

The test battery was also indicated whether or not it was activated by a conventional heat-sensitive paint. An irreversible heat-sensitive paint that changes color from light reddish purple to blue-violet when heated to 130 ° C. or higher was applied to the surface of the container. However, -55
In a low temperature environment of ° C., the surface temperature of the container rose only to 120 ° C., and no discoloration of the heat-sensitive paint was observed.

[0019]

According to the present invention, the presence or absence of activation is detected based on the temperature history inside the thermal battery, and the determination can be made even in a thermal battery having a structure in which the temperature of the entire container does not rise or in a use condition such as a low temperature. It is possible. In addition, in order to electrically detect the activation of the thermal battery, it is possible to perform an operation check at a location away from the thermal battery and collectively manage a plurality of thermal batteries.

[Brief description of the drawings]

FIG. 1 is a sectional view of a thermal battery showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Unit cell 2 Heating agent 3 Power generation part 4 Positive terminal 5 Negative terminal 6 Ignition ball 7 Ignition terminal 8 Insulation material 9 Container 10 Thermal fuse 11 Thermal fuse terminal

Claims (1)

(57) [Claims] 1. A thermal battery in which a unit cell and a heat generating agent are wrapped in a heat insulating material and housed in a closed container, wherein a thermal fuse which operates at an internal temperature of the activated thermal battery is incorporated, and the operating state of the thermal fuse is determined. A thermal battery comprising a terminal for detection.