JP2006210046A - Overheat protection element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an overheat protection element which realizes low resistance value at room temperature region and can shut off current by a rapid tripping action at the time of heat generation or the like of the circuit, and also provide its manufacturing method. <P>SOLUTION: The overheat protection element has a polymer matrix 1 containing no conductive material interposed between a pair of opposed metal foils 2, the contact faces 3 of the pair of metal foils 2 contacting the polymer matrix 1 are formed rough respectively, and the pair of metal foils 2 are contacted and made to flow current at the normal temperature, and are separated, based on expansion of the polymer matrix 1 and shut off current at the time of high temperatures. Since the metal foils 2 appropriately made rough are crimped on both surfaces of the polymer matrix 1 respectively, stable initial resistance value can be obtained and, furthermore, rapid tripping characteristics can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an overheat protection element that protects circuits, batteries, components, and the like of electrical and electronic equipment, and a method for manufacturing the same.

Although not shown, an overheat protection element in which conductive particles are dispersed in a polymer matrix is already known in the field of electrical and electronic equipment (see Patent Document 1). This type of overheat protection element is required to have characteristics that the room temperature resistance value is sufficiently low, that the change rate between the room temperature resistance value and the resistance value during operation is sufficiently large, and that the change in resistance value during repeated operation is small. .
Japanese Patent Laid-Open No. 2004-103848

  However, the conventional overheat protection element in which the conductive particles are dispersed in the polymer matrix has a structure in which the room temperature resistance value is increased by repeating the operation or the conductive polymer matrix is sandwiched between a pair of conductors. There is a problem that the polymer matrix itself becomes a resistance in the circuit when energized.

As a means for solving such a problem, a method is considered in which the conductors that become the electrodes are brought into direct contact with each other, and when the circuit is overheated, the conductors are separated from each other by detection of heat to cut off the energization.
However, if the contact surface between the conductors is flat, a slight bias in expansion occurs when the ambient temperature rises due to distortion during molding of the polymer matrix, and as a result, the current is cut off when the circuit overheats. There is a possibility that the trip temperature to be different is different for each overheat protection element. In addition, chattering or the like may occur near the trip temperature.

In addition, the above-mentioned patent document discloses an overheat protection element that utilizes expansion and contraction of an elastomer or silicone rubber sandwiched between a pair of conductors, and conductive particles are placed on a polymer matrix between the pair of conductors. A type that holds the dispersed PTC resin and maintains the stability is shown in the examples.
Although this type of overheat protection element can obtain stability, the structure becomes complicated, and this causes a problem that the manufacturing method becomes complicated and the cost increases.

  The present invention has been made in view of the above, and provides an overheat protection element capable of reducing a resistance value in a room temperature region and interrupting a current due to a sudden trip behavior when a circuit generates heat, and a method for manufacturing the same. The purpose is that.

In the present invention, in order to solve the above problem, a polymer matrix is sandwiched between a plurality of opposing conductors,
The contact surfaces of a plurality of conductors that are in contact with the polymer matrix are each formed to be rough so that the plurality of conductors can be brought into contact with each other at room temperature to be energized, and separated (separated) based on the expansion of the polymer matrix at high temperatures. It is characterized by that.

The polymer matrix preferably contains 70 wt% or more of a crystalline thermoplastic polymer and 1 wt% or more of maleic acid-modified EPR.
The conductor is preferably nickel, copper, and / or a plurality of alloys, and the roughness of the contact surface is preferably Ra 0.5 to 5 μm.

Further, in the present invention, in order to solve the above-described problem, a manufacturing method using a polymer matrix sandwiched between a plurality of opposing conductors,
The contact surfaces of a plurality of conductors that come into contact with the polymer matrix are each formed to be rough, the conductors can be brought into contact with each other at room temperature to be energized, and separated at the high temperature based on the expansion of the polymer matrix. .

The polymer matrix preferably contains 70 wt% or more of a crystalline thermoplastic polymer and 1 wt% or more of maleic acid-modified EPR.
Moreover, it is preferable that the conductor is made of nickel, copper, and / or a plurality of alloys, and the roughness of the contact surface is Ra 0.5 to 5 μm.

  Here, the polymer matrix in the claims may be one kind or plural kinds as long as it does not contain a conductive material. The overheat protection element can be used to protect at least a primary battery, a secondary battery, an automobile motor, a speaker, a mobile phone rechargeable battery, a computer circuit, and the like.

According to the present invention, there is an effect that the resistance value can be lowered in the room temperature region, and the current can be interrupted by a rapid trip behavior when the circuit generates heat.
Moreover, if the conductor is made of nickel, copper, and / or a plurality of alloys and the roughness of the contact surface is Ra 0.5 to 5 μm, excellent conductivity can be obtained at low cost, and the conductive state and insulation can be obtained. There is no chattering in which the states alternate.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. In the overheat protection element and the manufacturing method thereof according to the present embodiment, as shown in FIG. The metal foils 2 are sandwiched between a pair of metal foils 2 and used as lead terminals that serve as electrodes of a computer circuit.

  The polymer matrix 1 contains 70 wt% (wt%) or more of a crystalline thermoplastic polymer made of, for example, high-density polyethylene, polyethylene, or polypropylene, and is blended with 1 wt% or more of maleic acid-modified EPR, and is thin in a rectangular shape Molded into a sheet form.

  The metal foil 2 is made of, for example, rolled inexpensive nickel, copper, and / or a plurality of alloys, and the contact surface 3 that contacts the polymer matrix 1 is formed in rough unevenness. The roughness of the contact surface 3 is Ra is set in the range of 0.5 to 5 μm. Such a pair of metal foils 2 mesh with each other at normal temperature to energize the current, and function to separate from the polymer matrix 1 due to expansion of the polymer matrix 1 at high temperatures due to heat generation of the circuit.

  According to the above, since the flat metal foil 2 is not simply crimped to both surfaces of the polymer matrix 1, but the metal foil 2 having a suitably roughened surface is crimped, a stable initial resistance value can be obtained. In addition, steep trip characteristics can be obtained.

Examples of the overheat protection element and the method for manufacturing the same according to the present invention will be described below together with comparative examples. Example-1
First, pellets made of polyethylene (produced by Idemitsu Petrochemical Co., Ltd .: trade name 548B) and 3 wt% maleic acid-modified EPR (produced by Mitsui DuPont Polychemical Co., Ltd .: trade name NO903HC) as raw materials by a jet mill are used. The raw material was prepared to a particle size of 16 to 100 mesh, and this raw material was mixed and stirred by a super mixer (manufactured by Kawata), and kneaded by a pressure kneader adjusted to a temperature of 180 ° C. to obtain a kneaded product. When the kneaded material was obtained in this way, the kneaded material was set on a calender and sheeted to form a sheet having a thickness of 50 μm.

Next, the formed sheet is sandwiched between a pair of metal foils roughened to Ra: 1.0 μm, set in a press molding machine, heated (250 ° C.), pressurized (10 kgf / cm ² , 10 kgf / cm ² = 0.98 MPa) to obtain a laminate having a total thickness of 250 μm. The metal foil was a nickel foil having a thickness of 125 μm. The resulting laminate was irradiated with an electron beam of 5 MRad using an electron beam cross-linking device to cross-link the polymer blend, and then cut into a size of 5 mm × 12 mm to produce an overheat protection element.

Example-2
Basically, it was the same as Example-1, but a pair of metal foils roughened to Ra: 3.0 μm was used.
Comparative Example-1
Basically the same as in Example-1, except that the raw materials were 93 wt% polyethylene [manufactured by Idemitsu Petrochemicals: trade name 548B] and 7 wt% maleic acid-modified EPR [manufactured by Mitsui DuPont Polychemicals: trade name NO903HC]. It was. Moreover, a pair of metal foil roughened to Ra: 0.2 micrometer was used.

Comparative example-2
Basically the same as in Example-1, but a pair of metal foils roughened to Ra: 6.0 μm was used.
Comparative Example-3
Basically the same as in Example-1, except that the raw materials were 60 wt% polyethylene [made by Idemitsu Petrochemicals: trade name 548B] and 40 wt% maleic acid-modified EPR [made by Mitsui DuPont Polychemicals: trade name NO903HC]. It was. Moreover, a pair of metal foil roughened to Ra: 1.0 micrometer was used.

  When the overheat protection elements of Examples and Comparative Examples were manufactured, the PTC characteristics of each overheat protection element were measured. Specifically, one end of the electric wire was joined to the overheat protection element and the other end was connected to a resistance measuring device, and this overheat protection element was placed in an oven to start measuring the resistance value.

  In measurement, the resistance value is measured by increasing the temperature sequentially from 20 ° C. every 10 ° C., and the temperature is increased to 160 ° C. When reaching 160 ° C., the resistance value is measured by cooling every 10 ° C. Cooled to 20 ° C. When each measurement temperature was reached, the temperature was held for 10 minutes and the resistance value at that time was measured. After measuring the resistance at 20 ° C., the resistance value after 1 hour was measured by keeping the temperature at 20 ° C. for 1 hour, and this resistance value was taken as the final return resistance value.

  When the initial resistance (resistance value at 20 ° C. before temperature increase), the return resistance, and the return rate of Examples and Comparative Examples were measured, these were summarized in Tables 1 and 2. The PTC characteristics of the examples and comparative examples are summarized in the graphs of FIGS.

According to the overheat protection elements of Examples-1 and 2, good PTC characteristics could be obtained.
On the other hand, in the case of the overheat protection elements of Comparative Examples-1 and 2, chattering in which the conduction state and the insulation state alternated between the normal temperature state and the trip temperature was confirmed. Furthermore, in the case of the overheat protection element of Comparative Example-3, the increase in the resistance value with respect to the temperature increase was low, and no appearance of tripping was observed.

It is a section explanatory view showing typically an embodiment of an overheating protection element concerning the present invention, and its manufacturing method. It is a graph which shows the resistance value-temperature curve of the overheat protection element of the Example in the Example of the overheat protection element which concerns on this invention. It is a graph which shows the resistance value-temperature curve of the overheat protection element of the comparative example in the Example of the overheat protection element which concerns on this invention.

Explanation of symbols

1 Polymer matrix 2 Metal foil (conductor)
3 Contact surface

Claims (6)

  An overheat protection element with a polymer matrix sandwiched between a plurality of opposing conductors, each of which forms a rough contact surface of the plurality of conductors in contact with the polymer matrix and allows the plurality of conductors to contact each other at room temperature. An overheat protection element characterized in that it can be energized and separated at high temperatures based on expansion of the polymer matrix.   The overheat protection element according to claim 1, wherein the polymer matrix contains 70 wt% or more of a crystalline thermoplastic polymer and is blended with 1 wt% or more of maleic acid-modified EPR.   The overheat protection element according to claim 1 or 2, wherein the conductor is nickel, copper, and / or a plurality of alloys, and the roughness of the contact surface is Ra 0.5 to 5 µm. A method for manufacturing an overheat protection element that uses a polymer matrix sandwiched between a plurality of opposing conductors,
The contact surfaces of a plurality of conductors that are in contact with the polymer matrix are each roughly formed, and the plurality of conductors are brought into contact with each other at room temperature to be energized, and separated at the high temperature based on the expansion of the polymer matrix. Manufacturing method of overheat protection element.   The method for producing an overheat protection element according to claim 4, wherein the polymer matrix contains 70 wt% or more of a crystalline thermoplastic polymer and is blended with 1 wt% or more of maleic acid-modified EPR.   The method for manufacturing an overheat protection element according to claim 4 or 5, wherein the conductor is nickel, copper, and / or a plurality of alloys, and the roughness of the contact surface is Ra 0.5 to 5 µm.

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