JPH0877900A - Temperature protector - Google Patents

Abstract

PURPOSE: To provide a temperature protector on which a temperature bias can be imposed and by which actuating rapidity of an apparatus or the like to an overcurent temperature rise can be guaranteed. CONSTITUTION: A fusible metallic piece 2 is provided, and current-carrying is cut off by fusion of the fusible metallic piece 2. A resistance value by which a temperature bias (a bias temperature is higher by 10 deg.C or more than the normal temperature and is lower by 20 deg.C or more than a fusing point of the fusible metallic piece 2) can be imposed by self-heating of the fusible metallic piece by an ordinary time carrying electric current, is applied to the fusible metallic piece 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature protector used to protect an electric device, an electric component, or an electric element (hereinafter collectively referred to as an electric device or the like) from abnormal heat generation due to overcurrent. It is a thing.

[0002]

2. Description of the Related Art Conventionally, as a temperature protector, an alloy type temperature fuse, that is, a fuse element using a fusible metal piece is well known. In this alloy type temperature fuse, it is used by being attached to an electric device or the like to be protected at a position capable of receiving heat with high sensitivity, and the fusible metal piece is melted by heat generation due to overcurrent of the device, Molten metal is divided by spheroidizing deformation based on its surface tension,
Due to the further progress of spheroidization after the division, the distance between divisions reaches the arc extinction distance, and the electricity is cut off by the disappearance of the arc to prevent abnormal heating of equipment and the like.

In the above, the solidus temperature T of the soluble metal piece is
If there is a difference between a and the liquidus temperature Tb, the temperature range Ta to T
Since there is a possibility of melting at any temperature in b, and the greater the difference between the two temperatures (Tb-Ta), the greater the variation in operating temperature. It is necessary to use an alloy or one having a temperature difference of 2 to 3 ° C or less. It is also necessary to use, as the fusible metal piece of the alloy-type temperature fuse, one having excellent workability (drawability) and mechanical strength.

However, these various requirements (eutectic alloy or melting characteristics close thereto, workability, mechanical strength, etc.)
It is extremely difficult to cover all of the alloy composition that melts at a desired temperature with a narrow temperature interval, and due to such restrictions, at the present stage, the nominal operating temperature is 76 ° C, 102 ° C,
The alloy type temperature fuses of 115 ° C., 130 ° C., 150 ° C. and 169 ° C. actually exist.

Therefore, when protecting equipment or the like having an allowable temperature of 140 ° C., which is a temperature between 130 ° C. and 150 ° C., with the alloy type temperature fuse, the alloy type temperature fuse having a nominal operating temperature of 130 ° C. However, even though the equipment has sufficient heat resistance, the use of the equipment is interrupted, which is uneconomical in terms of heat resistant insulation.

Conventionally, a resistor is placed close to an alloy type temperature fuse, a temperature bias is applied to the alloy type temperature fuse by the heat of the resistor, and the bias temperature is changed to allow different allowable temperatures of the equipment. It is known to deal with
No. 3-7417).

According to this bias temperature method, the operating temperature (almost the melting point of the fusible metal piece) of the alloy type temperature fuse is T ₁
° C., the resistance value of the resistor r, the electric current i, resistor and alloy type thermal fuse - if the heat transfer resistance between the's is h, Ju resistor - alloy type by Le heat i ² r The constant heating temperature (bias temperature) T ₁ '° C of the temperature fuse is given by T ₁ ' = i ² rh + room temperature, and the ambient temperature rise value, that is, the temperature rise value of the equipment is (T ₁ -T ₁ ′) ° C., that is, (T ₁ −i ² rh
-At room temperature), the alloy type temperature fuse is activated, under the condition that the fusible metal piece is common (using the fusible metal piece with the same melting point), and when the energizing current is large, the ambient temperature is relatively low. When the temperature rise causes the alloy type temperature fuse to operate, and when the applied current becomes small, it becomes possible to operate the alloy type temperature fuse at a relatively high ambient temperature increase.

As long as the conventional alloy type temperature fuse is used for protection, the permissible temperature value of the equipment differs depending on the energizing current of the equipment (when the energizing current becomes large, the permissible temperature value becomes low and the energizing current becomes large). Is small, the allowable temperature value is high), even if these temperatures are, for example, above 130 ° C.
When the temperature is between 150 ° C and 150 ° C, the current is uniformly cut off by the alloy type temperature fuse with a nominal operating temperature of 130 ° C. In the above temperature bias method, the alloy type is selected according to the allowable temperature. The temperature fuse can be activated, and on the heat insulation,
Reasonable protection is also possible.

[0009]

However, in the conventional temperature bias method, it is necessary to closely couple the alloy type temperature fuse and the resistor, and it is inevitable that the size increase due to the coupling is unavoidable. Since it requires the addition of a material, for example, an adhesive, the heat resistance and heat capacity of the heat transfer medium from the outside to the fusible metal piece of the alloy-type temperature fuse are increased, and the alloy against an overcurrent temperature rise of equipment etc. It is unavoidable to slow down the fusing speed of the soluble metal pieces in the mold temperature fuse. Therefore, it is difficult to guarantee the quickness of operation.

It is an object of the present invention to be temperature biased,
Moreover, it is another object of the present invention to provide a temperature protector capable of guaranteeing quickness of operation against an increase in overcurrent temperature of equipment and the like.

[0011]

SUMMARY OF THE INVENTION A temperature protector according to the present invention has a fusible metal piece, and in a temperature protector in which the energization is cut off by melting of the fusible metal piece, the temperature protector is melted by a constant energizing current. A resistance value to which a temperature bias (a bias temperature is 10 ° C. or more higher than room temperature and 20 ° C. or more lower than the melting point of the fusible metal piece) by self-heating of the metal piece is given to the fusible metal piece. This is a configuration characterized by being performed.

[0012]

If the resistance value per unit length of the fusible metal piece is r, the energizing current is i, and the thermal resistance of the heat transfer medium from the fusible metal piece to the surrounding external space per unit length is H, The constant temperature (bias temperature) of the soluble metal piece of the temperature protector is given by [i ² rH + normal temperature]. And Thus, if the melting point of the soluble metal pieces and T _0, temperature protector - the outside temperature rises to [T ₀ -i ² rh-normal temperature], ie ,, Temperature protector - external temperature [T _0- i ² rH], the fusible metal piece is melted and the power supply to the equipment is cut off.

Conventionally, i ² rH≈0. Therefore, when the allowable temperature of the equipment is 140 ° C., the alloy type temperature protector (alloy type temperature fuse with a nominal operating temperature of 130 ° C.
When the equipment temperature reaches 130 ° C. by using No. 2), the use of the equipment is forced to be interrupted although there is still a heat resistant temperature margin of 10 ° C. On the other hand, in the temperature protector of the present invention, i ² rH (bias temperature with reference to room temperature) should be at least 10 ° C. and 20 ° C. or more lower than T ₀ (melting metal piece melting point). , The resistance value r of the fusible metal piece is set. For example, a fusible metal piece having a nominal operating temperature of 150 ° C. is used, and i ² rH (bias temperature based on room temperature) is set to 10 ° C. If the resistance value r of the fusible metal piece is set, the device temperature will be 140
When the temperature reaches ℃, the power can be cut off.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a case-type alloy-type fusible metal piece according to the present invention. In FIG. 1, 1 and 1 are lead wires arranged in a straight line, and 2 is a low melting point metal piece connected between the lead wires 1 and 1 by side contact or welding. 3 is a flux applied to the low melting point metal piece 2, which contains rosin such as pine resin as a main component, an activator,
For example, it is possible to use those to which a small amount of amine hydrochloride or the like has been added. Reference numeral 4 is a ceramic cylinder (usually made of alumina ceramics) covered on the flux-coated low melting point metal piece. Numerals 5 and 5 are epoxy resin materials that seal between each opening at both ends of the ceramic cylinder and each lead wire (usually a bare copper wire or an insulating coated copper wire is used), which is usually room temperature curable. Is.

FIG. 2A is a cross-sectional view showing another embodiment of the case type alloy-type fusible metal piece according to the present invention, and FIG. 2B is a sectional view of FIG. FIG. In FIG. 2A and FIG. 2B, 1 and 1 are lead wires juxtaposed to each other, and 2 is a low melting point connected between the lead wires 1 and 1 by side contact or welding. It is a metal piece. 3 is a flux coated on the low melting point metal piece 2. Reference numeral 41 is a flat insulating case (usually made of alumina ceramics), which is covered on the flux-coated low melting point metal piece and has an opening at only one end. Reference numeral 5 is an epoxy resin material that seals between the opening of the insulating case and the lead wires 1 and 1 (usually a bare copper wire or an insulating coated copper wire is used). Is room temperature curable.

FIG. 3A is an explanatory view showing an embodiment of the substrate type alloy-type fusible metal piece according to the present invention, and FIG. 3B.
[Fig. 4] is a cross-sectional view taken along line A-B of Fig. 3. In FIG. 3A and FIG. 3B, 40 is a ceramic substrate (usually alumina ceramics is used). Reference numerals 11 and 11 denote a pair of film electrodes provided on one surface of the ceramic substrate, and can be provided by a thick film method by printing / baking a conductive paste or a thin film method such as metal deposition or electrodeposition. Reference numeral 2 is a low melting point metal piece connected between the membrane electrodes 11 and 11 by contact or welding. 3 is a flux applied to the low melting point metal piece. Numerals 1 and 1 are lead wires (usually insulating coated copper wires or bare copper wires are used) connected to each of the membrane electrodes 11 and 11 by contact or welding. Reference numeral 50 denotes an epoxy resin material coated on one surface of the ceramic substrate 40, which is usually room temperature curable, as described above.

In the above, the resistance value r of the soluble metal piece 2 per unit length is given by r = ρ / s, where s is the cross-sectional area of the soluble metal piece 2 and ρ is the specific resistance value. . Thus, if the thermal resistance between the fusible metal piece per unit length of the temperature protector and the external space of the temperature protector is H and the energizing current is i, the fusible metal based on the Jule heat Constant heating temperature T ₁ '(bias temperature)
Is given by T ₁ '= i ² Hρ / s + normal temperature.

If the permissible temperature of the equipment to be protected is T ₁ (thus, the permissible temperature rise value is T ₁ −normal temperature) and the melting point of the fusible metal piece is T ₀ , (T ₀ −T ₁ ') is (T ₁
-At room temperature) or slightly smaller (less than 5 ° C) so that the cross-sectional area s of the fusible metal strip is
Is set so as to satisfy s≈i ² Hρ / (T ₀ −T ₁ ).

In the conventional alloy type temperature fuse, the self-heating temperature of the fusible metal piece due to the applied current is substantially zero (2 ° C. or less), and the self-heating temperature of the fusible metal piece is set to the alloy type temperature. It is impossible to use it as the fuse bias temperature. Therefore, in the temperature protector according to the present invention, the constant temperature T ₁ ′ of the soluble metal piece based on the jule heat is kept at room temperature so that the temperature bias can be effectively applied at the self-heating temperature of the soluble metal piece. The resistance value of the soluble metal piece is set so as to be higher by 10 ° C. or more.

In the temperature protector according to the present invention, when the ambient temperature rise value reaches (T ₀ -T ₁ ′), the operation starts, but the allowable temperature rise value of the equipment is usually 20 ° C.
The above is the above, and accordingly, the constant temperature T ₁ ′ of the soluble metal piece based on the temperature protector heat is set to the melting point T _{0 of the} soluble metal piece.
The resistance value of the fusible metal piece is set so as to satisfy the condition of lowering it by 20 ° C. or more.

In the temperature protector of the present invention, the soluble metal composition (76 ° C, 102 ° C,
115 ° C, 130 ° C, 150 ° C and 169 ° C), and the kind of the soluble metal piece so that the power to the equipment is cut off at a temperature equal to its allowable temperature or slightly lower (within 5 ° C). Is selected and the resistance value of the soluble metal piece is set. For example, for a device having an allowable temperature of 140 ° C., the bias temperature is 10 ° C. Therefore, the resistance of the soluble metal piece is set so that the constant temperature (bias temperature) of the soluble metal piece is (10 ° C. + normal temperature). The value is set, and the fusible metal piece is selected to have a nominal operating temperature of 150 ° C, so that the device can be turned off at an allowable temperature of 140 ° C.

In the temperature protector according to the present invention, the permissible temperature of the device is set low as the energizing current of the device or the like becomes large, and the permissible temperature of the device as the energizing current of the device or the like becomes small. Is particularly preferably used when (i) is set high (in the formula, even when the energizing current i becomes large, the device allowable temperature T ₁ is decreased, or even when the energizing current i becomes small, If the device allowable temperature T ₁ is increased, the same temperature protector can be used as long as the equation holds.

[0023]

The temperature protector according to the present invention is constructed as described above, and a temperature bias of a predetermined temperature is applied to the conventional alloy type temperature fuse by the self-jule heat generation of the fusible metal piece. Since the resistance value of the fusible metal piece is set so as to apply, a resistor is placed close to the alloy type temperature fuse,
Unlike conventional temperature protectors, in which the fusible metal piece is temperature-biased by the resistor's juule heat generation, the overall compactness can be maintained and the thermal resistance from the outside of the temperature protector to the fusible metal piece can be maintained. Can be maintained sufficiently low, and the quick actuation of the soluble metal piece against temperature rise due to overcurrent of equipment can be well guaranteed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

2 (a) is a sectional view showing another embodiment of the present invention, and FIG. 2 (b) is a sectional view of FIG. 2 (a).
FIG.

3 (A) is an explanatory view showing an embodiment of the present invention different from the above, and FIG. 3 (B) is a flowchart in FIG. 3 (A).
FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lead wire 2 Low melting point metal piece 3 Flux 4 Ceramics cylinder 5 Epoxy resin material 11 Membrane electrode 41 Insulation case 40 Ceramics substrate 50 Epoxy resin material

Claims (2)

[Claims] 1. A temperature protector having a fusible metal piece and interrupting energization by fusing the fusible metal piece, wherein a resistance value to which a temperature bias is applied by self-heating of the fusible metal piece due to a constant energizing current. Is attached to the soluble metal piece. 2. The temperature protector according to claim 1, wherein the bias temperature is higher than room temperature by 10 ° C. or more and lower than the melting point of the soluble metal piece by 20 ° C. or more.