JP3878728B2

JP3878728B2 - Thin temperature fuse

Info

Publication number: JP3878728B2
Application number: JP32239397A
Authority: JP
Inventors: 俊朗川西
Original assignee: Uchihashi Estec Co Ltd
Current assignee: Uchihashi Estec Co Ltd
Priority date: 1997-11-06
Filing date: 1997-11-06
Publication date: 2007-02-07
Anticipated expiration: 2017-11-06
Also published as: JPH11144581A

Description

【０００１】
【産業上の利用分野】
本発明はヒュ−ズエレメントに低融点合金片を使用した薄型温度ヒュ−ズに関するものである。
【０００２】
【従来の技術】
電気機器・電子機器を過電流に基づく異常発熱から保護するための温度ヒュ−ズとして合金タイプが周知されている。
この合金タイプの温度ヒュ−ズにおいては、ヒュ−ズエレメントにフラックス塗布の低融点金属片を使用しており、機器の過電流に基づく異常発熱時にその発熱で低融点合金片を溶融させ、既に溶融されているフラックスとの共存下、溶融合金が表面張力による球状化で分断され、球状化の進行でその分断距離が所定の距離に達したときに通電が遮断されて機器が電源から切り離される。
【０００３】
近来、電気・電子機器の小型化に伴い、これらの機器に装着して使用される温度ヒュ−ズにおいても、小型化、特に、薄厚化が要求され、最近では厚さ４００μｍもの超薄型が要求されている。
しかしながら、このような超薄型の温度ヒュ−ズでは、扁平ケ−ス内の空間ギャップが極めて薄く低融点合金片が溶融されても、その溶融金属がケ−ス内面間にブリッジして即時に溶断され難く、従って、上記表面張力による球状化分断では、低融点金属片が溶融されたのち分断されるまでに相当に時間がかかり、作動の迅速性を保証し難い。
【０００４】
そこで、本発明者においては、「扁平ケ−ス内に低融点合金片をケ−ス厚み方向に貫設し、そのケ−ス内に弾性材を低融点合金片の剪断反力に抗して納め、低融点合金片の剪断強度が溶融により低下するとその溶融合金片を弾性材の復元力で即時に強制的に剪断すること」を既に提案した（特開平９−１７３０１号）。
この温度ヒュ−ズでは、温度ヒュ−ズの作動時、低融点合金片が弾性材の復元力で剪断され得る程度に軟化されればよく、該溶融合金の強面張力による球状化が要求されないから、球状化分断を促すためのフラックスや低融点合金片の酸化防止のための気密性が不要となり、それだけ温度ヒュ−ズの構成の簡易化を図り得る利点もある。
【０００５】
【発明が解決しようとする課題】
しかしながら、上記特開平９−１７３０１号に開示した温度ヒュ−ズでは、平常時、低融点合金片が弾性材から常時剪断力を受け、その剪断力で低融点合金片がクリ−プ変形して細くなり発熱し、この発熱で溶断する畏れがあること、また、弾性材が伸びて剪断応力が減退し、低融点合金片が溶融しても迅速な強制的剪断が生じ難いこと、等の不具合が懸念される。
【０００６】
本発明の目的は、ヒュ−ズエレメントとして低融点合金片を使用し、作動時、溶融された低融点合金片を強制的に剪断する温度ヒュ−ズにおいて、平常時での低融点合金片のクリ−プ変形を排除しつつ誤作動なく迅速作動を保証することにある。
【０００７】
【課題を解決するための手段】
請求項１に係る薄型温度ヒューズは、扁平ケースの両面に電極が設けられ、これらの電極間に低融点合金片が扁平ケースの厚み方向の向きで接続され、線状の熱収縮性片が前記低融点合金片の前方を回って配され、同低融点合金片の後方に配された両端が扁平ケース内に固定され、前記低融点合金片が溶融される温度で前記の線状熱収縮性片が低融点合金片の位置を越えて収縮されるように設置されていることを特徴とする。
請求項２に係る薄型温度ヒューズは、扁平ケースの両面に電極が設けられ、これらの電極間に低融点合金片が扁平ケースの厚み方向の向きで接続され、熱収縮性片の一端が扁平ケース内に固定され、この熱収縮性片の他端部に前記低融点合金片が貫通されていることを特徴とする。
【０００８】
【発明の実施の形態】
以下、本発明の実施例を図面を参照しつつ説明する。
図１の（イ）は本発明に係る薄型温度ヒュ−ズの一例を示す図面、図１の（ロ）は図１の（イ）におけるロ−ロ断面図である。
図１の（イ）及び図１の（ロ）において、１は絶縁物、例えばセラミックス製やプラスチック製の扁平ケ−スであり、胴枠部１０に上下蓋板部１１，１２が一体化されている。２１，２２は扁平ケ−ス１の蓋板部１１，１２の外面に設けられた電極であり、導電金属板や導電金属箔の貼着、導電ペ−ストの塗布・焼付け、導電金属材の蒸着やメッキ等で形成することができる。３は扁平ケ−ス１の厚み方向に貫通された低融点金属片であり、各端が各電極２１，２２に溶接等で接続されている。４は熱収縮性片であり、一端４１がケ−ス内面に固定され、他端部に前記の低融点合金片３が貫通されている。
この熱収縮性片には、延伸プラスチックフィルムや形状記憶させたプラスチック成形体を使用することができる。この熱収縮性片は非絶縁性であっても差し支えなく、形状記憶合金の使用も可能である。
【０００９】
上記において、低融点合金片３の融点Ｔ₁（非共晶合金の場合は固相線温度）が温度ヒュ−ズの作動温度として設定されている。
上記熱収縮性片４には、温度Ｔ₁以下で急速に収縮し、平常時の機器の通電サイクル下での加熱では実質上収縮しないものが使用されている。
本発明に係る温度ヒュ−ズは、例えばリチウムイオン２次電池の安全弁板と正極蓋との間に挾持して使用される。
図２は本発明に係る温度ヒュ−ズの作動状態を示し、機器の過電流に基づく異常発熱で低融点合金片３が溶融され、この際、熱収縮性片４が既に加熱されてその熱収縮性により引張力を発生しているので、その引張力で溶融合金３が強制的に剪断される。
この場合、熱収縮性片４の熱収縮率をｋ，厚さをｔ，巾をｂ，熱収縮時でのヤング率をＥとすれば、剪断力Ｆは、
Ｆ＝Ｅｋｔｂ ▲１▼
で与えられ、
溶融した低融点合金片の剪断破断応力をτ、低融点合金片の断面積をＳとすれば、
Ｅｋｔｂ＞τＳ ▲２▼
が条件とされる。
【００１０】
上記熱収縮性片４の熱収縮は、歪状態で冷却凍結されたポリマ−の分子鎖や未結晶状態が加熱軟化により解放、結晶化されることにより生じ、上記のヤング率Ｅは常温時のヤング率に較べて小である。しかしながら、ケ−ス内空間を最大限に利用し、ｔｂを極力大とすること（厚さｔについては、ケ−ス内空間の厚みにほぼ等しくする）及びＳを可及的に小とすることにより、上記▲２▼の条件を容易に充足させ得、溶融した低融点合金片を確実に剪断できる。
この溶融合金片の強制剪断で低融点合金片のケ−ス内部分を元の位置から分離隔離でき、図２に示すように、元の位置の残存低融点合金片部分の分離ギャップｇを充分に大きくできるので、通電遮断を確実かつ迅速に行わせることができる。
【００１１】
図３の（イ）及び図３の（ロ）〔図３の（イ）におけるロ−ロ断面図〕は本発明に係る薄型温度ヒュ−ズの別例を示し、図４はその別例の作動状態を示している。
図３において、１は扁平ケ−ス、２１，２２は電極、３は低融点合金片であり、これらは上記図１に示したものと実質的に同じとされている。４は線状の熱収縮性片であり、弛み状態で両端４１，４１がケ−ス内面に固定され、低融点合金片の加熱溶融時での熱収縮性片４の熱収縮で図４に示すように低融点合金片の位置ｐを越えて短縮するように設定されている。
【００１２】
【発明の効果】
本発明に係る薄型温度ヒュ−ズにおいては、低融点合金片をその溶融と同時に熱収縮性片で強制的に剪断できるので、溶融した低融点合金片を表面張力により球状化分断させる場合に較べ迅速に分断作動させ得る。また、熱収縮性片では平常時に低融点合金片に剪断力を作用させることがないから、低融点合金片のクリ−プ破断等による誤作動を排除できる。
従って、扁平ケ−ス内のギャップを使用電圧下での放電を防止できるに足る小間隙としても、誤作動なく迅速に作動させ得、温度ヒュ−ズの超薄型化が可能となる。
また、球状化分断を促すためのフラックスや低融点合金片の酸化防止のための気密性が不要となり、それだけ温度ヒュ−ズの構成を簡易にできるから、かかる点からも一層の薄型化を図ることができる。
【図面の簡単な説明】
【図１】図１の（イ）は本発明に係る薄型温度ヒュ−ズの一例を示す図面、図１の（ロ）は図１の（イ）におけるロ−ロ断面図である。
【図２】図１に示す薄型温度ヒュ−ズの作動状態を示す図面である。
【図３】図３の（イ）は本発明に係る薄型温度ヒュ−ズの別例を示す図面、図３の（ロ）は図３の（イ）におけるロ−ロ断面図である。
【図４】図３に示す薄型温度ヒュ−ズの作動状態を示す説明図である。
【符号の説明】
１扁平ケ−ス
２１電極
２２電極
３低融点合金片
４熱収縮性片[0001]
[Industrial application fields]
The present invention relates to a thin temperature fuse using a low melting point alloy piece as a fuse element.
[0002]
[Prior art]
Alloy types are well known as temperature fuses for protecting electrical and electronic devices from abnormal heat generation due to overcurrent.
In the temperature fuse of this alloy type, a flux-coated low melting point metal piece is used for the fuse element, and the low melting point alloy piece is melted by the heat generated in the event of abnormal heat generation due to overcurrent of the equipment. In the coexistence with the melted flux, the molten alloy is divided by spheroidization due to surface tension, and when the spheroidization progresses, the current is cut off and the device is disconnected from the power supply. .
[0003]
Recently, with the miniaturization of electrical and electronic equipment, the temperature fuse used by attaching to these equipment is also required to be downsized, in particular, thin, and recently the ultra-thin thickness of 400 μm is required. It is requested.
However, in such an ultra-thin temperature fuse, even if the space gap in the flat case is extremely thin and the low melting point alloy piece is melted, the molten metal bridges between the inner surfaces of the case and immediately. Therefore, in the spheroidizing division by the above surface tension, it takes a considerable time until the low melting point metal piece is melted and then it is difficult to guarantee the speed of operation.
[0004]
Therefore, the present inventor stated that “a low melting point alloy piece is penetrated in the flat case in the thickness direction of the case, and an elastic material is resisted against the shear reaction force of the low melting point alloy piece in the case. It has already been proposed that when the shear strength of the low melting point alloy piece decreases due to melting, the molten alloy piece is immediately and forcibly sheared by the restoring force of the elastic material (Japanese Patent Laid-Open No. 9-17301).
In this temperature fuse, when the temperature fuse is operated, it is sufficient that the low melting point alloy piece is softened to such an extent that it can be sheared by the restoring force of the elastic material, and spheroidization due to the strong surface tension of the molten alloy is not required. Further, there is an advantage that the flux for promoting spheroidization and the airtightness for preventing oxidation of the low melting point alloy piece are unnecessary, and the structure of the temperature fuse can be simplified accordingly.
[0005]
[Problems to be solved by the invention]
However, in the temperature fuse disclosed in the above Japanese Patent Laid-Open No. 9-17301, the low melting point alloy piece normally receives a shearing force from the elastic material, and the shearing force causes the low melting point alloy piece to creep. There are problems such as thinning and heat generation, and there is a possibility of fusing by this heat generation, and that the elastic material stretches and shear stress decreases, and even if the low melting point alloy piece melts, rapid forced shearing is difficult to occur. Is concerned.
[0006]
It is an object of the present invention to use a low melting point alloy piece as a fuse element, and in a temperature fuse that forcibly shears the molten low melting point alloy piece during operation, The purpose is to ensure quick operation without malfunction while eliminating creep deformation.
[0007]
[Means for Solving the Problems]
The thin thermal fuse according to claim 1 is provided with electrodes on both sides of the flat case, low melting point alloy pieces are connected between these electrodes in the direction of the thickness direction of the flat case, and the linear heat-shrinkable pieces are The linear heat shrinkability at a temperature at which the low melting point alloy piece is arranged around the front of the low melting point alloy piece and both ends arranged at the rear of the low melting point alloy piece are fixed in a flat case and the low melting point alloy piece is melted. The piece is installed so as to be shrunk beyond the position of the low melting point alloy piece.
The thin thermal fuse according to claim 2 is provided with electrodes on both sides of the flat case, a low melting point alloy piece is connected between these electrodes in the thickness direction of the flat case, and one end of the heat shrinkable piece is the flat case. The low-melting-point alloy piece is penetrated through the other end of the heat-shrinkable piece.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1 (a) is a drawing showing an example of a thin temperature fuse according to the present invention, and FIG. 1 (b) is a cross-sectional view of FIG. 1 (b).
In FIG. 1A and FIG. 1B, reference numeral 1 denotes an insulator, for example, a flat case made of ceramics or plastic, and upper and lower cover plate portions 11 and 12 are integrated with the body frame portion 10. ing. Reference numerals 21 and 22 denote electrodes provided on the outer surface of the cover plate portions 11 and 12 of the flat case 1, adhesion of conductive metal plates and conductive metal foils, application and baking of conductive paste, It can be formed by vapor deposition or plating. Reference numeral 3 denotes a low melting point metal piece penetrating in the thickness direction of the flat case 1, and each end is connected to each electrode 21, 22 by welding or the like. Reference numeral 4 denotes a heat-shrinkable piece, one end 41 is fixed to the inner surface of the case, and the low melting point alloy piece 3 is passed through the other end.
For the heat-shrinkable piece, a stretched plastic film or a plastic molded body having a shape memory can be used. This heat-shrinkable piece can be non-insulating, and a shape memory alloy can be used.
[0009]
In the above, the melting point T ₁ (solidus temperature in the case of a non-eutectic alloy) of the low melting point alloy piece 3 is set as the operating temperature of the temperature fuse.
As the heat-shrinkable piece 4, a piece that rapidly shrinks at a temperature T ₁ or less and that does not substantially shrink when heated under a current-carrying cycle of a normal device is used.
The temperature fuse according to the present invention is used, for example, by being sandwiched between a safety valve plate and a positive electrode cover of a lithium ion secondary battery.
FIG. 2 shows the operating state of the temperature fuse according to the present invention, where the low melting point alloy piece 3 is melted due to abnormal heat generation due to the overcurrent of the equipment. At this time, the heat shrinkable piece 4 has already been heated and the heat Since the tensile force is generated by the shrinkage, the molten alloy 3 is forcibly sheared by the tensile force.
In this case, if the heat shrinkage rate of the heat shrinkable piece 4 is k, the thickness is t, the width is b, and the Young's modulus at the time of heat shrinkage is E, the shear force F is
F = Ektb (1)
Given in
If the shear fracture stress of the melted low melting point alloy piece is τ and the cross sectional area of the low melting point alloy piece is S,
Ektb> τS (2)
Is a condition.
[0010]
The heat shrinkage of the heat-shrinkable piece 4 is caused by releasing and crystallizing a molecular chain and an uncrystallized state of a polymer that has been cooled and frozen in a strained state by heat softening. Small compared to Young's modulus. However, the space in the case is utilized to the maximum, tb is maximized (the thickness t is approximately equal to the thickness of the space in the case), and S is made as small as possible. Thus, the condition (2) can be easily satisfied, and the molten low melting point alloy piece can be reliably sheared.
By forced shearing of the molten alloy piece, the portion in the case of the low melting point alloy piece can be separated and separated from the original position, and as shown in FIG. 2, the separation gap g of the remaining low melting point alloy piece portion at the original position is sufficiently large. Therefore, it is possible to reliably and quickly cut off the energization.
[0011]
3 (a) and 3 (b) (a cross-sectional view of the roll in FIG. 3 (a)) show another example of a thin temperature fuse according to the present invention, and FIG. Indicates the operating state.
In FIG. 3, 1 is a flat case, 21 and 22 are electrodes, 3 is a low melting point alloy piece, and these are substantially the same as those shown in FIG. 4 is a linear heat-shrinkable piece. Both ends 41 and 41 are fixed to the inner surface of the case in a slack state, and the heat-shrinkable piece 4 is thermally contracted when the low-melting-point alloy piece is heated and melted. As shown, it is set to shorten beyond the position p of the low melting point alloy piece.
[0012]
【The invention's effect】
In the thin temperature fuse according to the present invention, since the low melting point alloy piece can be forcibly sheared with the heat shrinkable piece simultaneously with its melting, it is compared with the case where the molten low melting point alloy piece is spheroidized by surface tension. It can be activated quickly. Further, since the heat-shrinkable piece does not cause a shearing force to act on the low-melting-point alloy piece in normal times, malfunction due to creep rupture or the like of the low-melting-point alloy piece can be eliminated.
Therefore, even if the gap in the flat case is a small gap sufficient to prevent discharge under the operating voltage, it can be operated quickly without malfunction, and the temperature fuse can be made ultra-thin.
Further, the flux for promoting spheroidization and the airtightness for preventing oxidation of the low melting point alloy piece are not required, and the temperature fuse can be simplified accordingly. be able to.
[Brief description of the drawings]
FIG. 1A is a drawing showing an example of a thin temperature fuse according to the present invention, and FIG. 1B is a cross-sectional view of FIG.
FIG. 2 is a view showing an operating state of the thin temperature fuse shown in FIG. 1;
3 (a) is a view showing another example of the thin temperature fuse according to the present invention, and FIG. 3 (b) is a cross-sectional view of the roll in FIG. 3 (a).
4 is an explanatory view showing an operating state of the thin temperature fuse shown in FIG. 3; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Flat case 21 Electrode 22 Electrode 3 Low melting-point alloy piece 4 Heat-shrinkable piece

Claims

Electrodes are provided on both sides of the flat case, low melting point alloy pieces are connected between these electrodes in the thickness direction of the flat case, and linear heat-shrinkable pieces are arranged around the front of the low melting point alloy pieces. The both ends of the low melting point alloy piece are fixed in the flat case, and the linear heat shrinkable piece exceeds the position of the low melting point alloy piece at a temperature at which the low melting point alloy piece is melted. Thin thermal fuse, which is installed so as to be shrunk .

Electrodes are provided on both sides of the flat case, low melting point alloy pieces are connected between these electrodes in the direction of the thickness direction of the flat case, and one end of the heat shrinkable piece is fixed in the flat case. A thin-film thermal fuse, wherein the low-melting-point alloy piece is penetrated through the other end portion.