JP3889855B2 - Substrate type temperature fuse - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substrate type temperature fuse having a large current capacity.
[0002]
[Prior art]
In the alloy type temperature fuse, a low melting point soluble alloy piece is used for the fuse element, and it is used by being attached to an electric device. When the electric device generates heat due to overcurrent, the generated heat generates a temperature fuse. The fuse element is melted, and the molten metal is divided by spheroidization based on the interfacial energy, and the device is prevented from being heated abnormally and thus generating a fire by being cut off from the power source of the device.
As an alloy type temperature fuse, as shown in FIG. 3, a pair of membrane electrodes 12 'and 12' are provided on an insulating substrate 11 'having good heat conductivity, for example, a ceramic plate, and each membrane electrode 12' has a lead wire. A low melting point soluble alloy piece 14 'is connected between the membrane electrodes, and a flux 15' is applied to the low melting point soluble alloy piece 14 '. A so-called substrate-type temperature fuse in which a molten alloy piece is covered and an insulator 16 'is covered is known.
This substrate type temperature fuse is advantageous for reducing the thickness of the alloy type temperature fuse. Also, the membrane electrode is several μm thick and has high heat conduction resistance. When soldering the lead wire to the equipment, it conducts the heat of soldering to the low melting point soluble alloy piece via the lead wire. Since it can be well blocked by the membrane electrode, there is an advantage that damage of the temperature fuse during soldering can be easily prevented.
[0003]
[Problems to be solved by the invention]
Usually, the temperature fuse is used to protect an electric device or circuit having a relatively small energizing current, and the current fuse is used to protect an electric device or circuit having a large energizing current.
However, the current state is that the current fuse cannot always be appropriately dealt with by the current fuse.
[0004]
Thus, in order to adapt the substrate type temperature fuse to the intermediate current region in terms of current capacity, the outer diameter of the fuse element needs to be approximately 1.0 mmφ or more. According to the inventor's investigation results, such a substrate type temperature fuse has a low operating speed and is difficult to operate satisfactorily as a temperature fuse.
For example, in FIG. 3, a low-melting-point soluble alloy having a ceramic insulating substrate thickness of 0.6 mm, a distance L ′ between membrane electrodes of 0.8 mm, a fuse element with a melting point of 126 ° C., and a cross-sectional area of 0.4 mm ² When a substrate-type temperature fuse using a piece is immersed in an oil having a temperature of 130 ° C., the fuse element is blown out in about 20 seconds, whereas the cross-sectional area of the fuse element is about 3 times 1 If it is ² mm ² , it takes about 40 seconds to fuse the fuse element, the operation speed is too slow, and a satisfactory protective function cannot be expected.
[0005]
As described above, when the wire diameter of the low melting point soluble alloy piece is increased, the operation takes time. (1) The main heat transfer path of the substrate type temperature fuse penetrates the substrate from the back surface of the insulating substrate. This is a route to the inside of the low melting point soluble alloy piece. When the diameter of the low melting point soluble alloy piece increases, the heat capacity of the low melting point soluble alloy piece increases to the melting point of the low melting point soluble alloy piece. (2) The time required for heating is increased, and (2) the membrane electrode and the insulating coating layer are in intimate contact with each other, and movement due to wetting of the melted low melting point soluble alloy to the membrane electrode is unlikely to occur inherently. Even when the diameter of the low melting point soluble alloy piece increases and the amount of molten alloy increases, the amount of movement due to wetting with the membrane electrode does not change, and a large amount of molten alloy remains between the membrane electrodes. Etc.
[0006]
An object of the present invention is to provide a substrate type temperature fuse having a large current capacity and a high operating speed.
[0007]
[Means for Solving the Problems]
The substrate-type temperature fuse according to the present invention is a thermal fuse in which a low-melting-point soluble alloy piece is melted by heat generated by an electric device, and this molten metal is divided by wetting and spreading to an electrode. A pair of membrane electrodes is provided on an insulating substrate, a plurality of low melting point soluble alloy pieces are connected in parallel between these membrane electrodes, and flux is applied to these low melting point soluble alloy pieces. The low melting point soluble alloy in the other membrane electrode has a structure characterized by covering the fusible alloy piece and covering the insulator, and the interval between the connection points of the low melting point soluble alloy pieces in one membrane electrode. For example, one membrane electrode has an arc shape, the other membrane electrode has a land located within the arc shape, and a plurality of low-melting-point soluble alloy pieces are both arranged. Radial connections can be made between the membrane electrodes. The cross-sectional area of each of the above low melting point soluble alloy pieces is 0.8 mm
The following is desirable.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a drawing showing an example of a substrate-type temperature fuse according to claim 1.
In FIG. 1, reference numeral 11 denotes a heat-resistant insulating substrate having good thermal conductivity, and for example, an alumina ceramic plate having a thickness of 0.1 mm to 1.0 mm can be used. Reference numerals 12 and 12 denote a pair of membrane electrodes provided on an insulating substrate. The thickness is usually 5 μm to 100 μm, and can be formed by printing and baking a conductive paste such as silver paste. Reference numeral 13 denotes a lead wire connected to each membrane electrode 12. 14 are a plurality of low-melting-point soluble alloy pieces connected between the membrane electrodes, and each low-melting-point soluble alloy piece 14 has a round wire with a cross-sectional area of 0.8 mm ² or less, preferably 0.4 mm ² or less. And foil is used. 15 is a flux applied on the low melting point soluble alloy pieces 14,... 16 is an insulator covering and covering the low melting point soluble alloy pieces and the electrodes, and can be formed, for example, by dipping coating of an epoxy resin.
[0009]
In the above embodiment, the distance between the connection points of the low melting point soluble alloy pieces in the membrane electrode is the same in both film electrodes, but compared to the distance between the connection points of the low melting point soluble alloy pieces in one of the membrane electrodes. The interval between the connection points of the low melting point soluble alloy pieces in the other membrane electrode can be narrowed.
[0010]
2 (a) is a drawing showing an example of a substrate type temperature fuse according to claim 3, and FIG. 2 (b) is a cross-sectional view of FIG. 2 (b).
In FIG. 2, 11 is an insulating substrate. Reference numeral 121 denotes one arcuate membrane electrode, and 122 denotes the other membrane electrode formed of lands in the arcuate shape, and includes a lead wire connecting ear 123. Reference numerals 13 and 13 denote lead wires connected to the respective membrane electrodes 121 and 122. 14, are a plurality of low-melting-point soluble alloy pieces radially connected between both membrane electrodes, using a round wire or foil having a cross-sectional area of 0.8 mm ² or less, preferably 0.4 mm ² or less. is there. Reference numeral 17 denotes an insulating spacer whose inner contour is larger than the outer periphery of the arc-shaped film electrode 121 and whose outer contour is slightly smaller than the outer contour of the insulating substrate 11, for example, a ceramic plate, and has a lead wire groove 171. The arc-shaped membrane electrode 121 is placed on the insulating substrate 11. Reference numeral 15 denotes a flux applied to the low melting point soluble alloy piece 14, and 16 denotes an insulator coated in the insulating spacer 17. The inner surface of the insulating spacer 17 is sufficiently larger than the outer shape of the arc-shaped film electrode 121. Since it is enlarged, the charging site including the arcuate membrane electrode 121 is deeply embedded in the insulator 15.
[0011]
The substrate-type temperature fuse according to the present invention is attached to a portion where heat generation based on an overcurrent of a protected device is easily received, and is used by being connected in series to the input end of the device. Thus, when an electric device generates heat due to an overcurrent, the fuse element of the temperature fuse is melted by the generated heat, the molten metal is divided by spheroidization based on the interfacial energy, and the device is powered Is cut off from.
In this case, the main transfer path of heat to the low-melting-point soluble alloy piece is a path that passes vertically from the outer surface of the insulating substrate to the center of the low-melting-point soluble alloy piece, The larger the diameter, the larger the volume of the low melting point soluble alloy piece and the longer the melting time of the low melting point soluble alloy piece. In addition, the molten low melting point soluble alloy piece moves by being pulled by the interfacial tension toward the membrane electrode in order to get wet to the membrane electrode, but this movement amount largely depends on the wettability of the membrane electrode. If the flow rate is the same, the flow rate of movement does not change, and the membrane electrode and the insulating coating layer are in intimate contact with each other. Therefore, when the diameter of the low-melting-point soluble alloy piece becomes large and the volume of the low-melting-point soluble alloy piece becomes large, the amount of the molten alloy remaining between the electrodes increases so that it becomes difficult to cause division.
[0012]
The present inventor shows the relationship between the cross-sectional area and outer diameter of the low melting point soluble alloy piece and the operating time of the substrate type temperature fuse, and the substrate type temperature fuse is equal to the melting point of the low melting point soluble alloy piece +4. As a result of immersing in oil at 0 ° C., it was found that if the cross-sectional area of the low melting point soluble alloy piece is 0.8 mm ² or less, the operation time can be suppressed within 20 seconds.
In the substrate type temperature fuse according to the present invention, the cross-sectional area of the low melting point soluble alloy piece is set to 0.8 mm ² or less based on this knowledge.
[0013]
In the substrate type temperature fuse according to the present invention, a plurality of low melting point soluble alloy pieces are connected in parallel, and it is difficult to make the operating time of each low melting point soluble alloy piece strictly the same. Since some variation is unavoidable, and it is not always heated uniformly, any one of the low melting point soluble alloy pieces connected in parallel is divided with priority in time, and thereafter one after another Go divided. In this case, since the current flowing through the remaining low melting point soluble alloy piece is increased by the division of one low melting point soluble alloy piece, the remaining low melting point soluble alloy piece is also heated by the Joule heat generation. The cutting time can be accelerated, and the operation of the entire substrate type temperature fuse can be speeded up from this point of view.
Furthermore, even if the area is small, such as the membrane electrode consisting of the land of the low melting point soluble alloy piece, the interval between the low melting point soluble alloy piece connecting portions becomes narrow, so that the membrane electrode is pulled in by wetting. Since the molten alloys are agglomerated with each other and the agglomeration force also contributes to the division, the speed of operation can be well maintained.
[0014]
In the substrate-type temperature fuse according to the present invention, the parallel number of the low-melting-point soluble alloy pieces is determined by the required current capacity, and is usually 3-10.
[0015]
【Example】
[Example 1]
In FIG. 1, an alumina ceramic plate having a thickness of 0.6 mm is used as an insulating substrate, a membrane electrode is formed by printing and baking a silver paste, the width of the membrane electrode is 0.8 mm, the length is 3.0 mm, and the membrane The distance between the electrodes is 1.2 mm, the low melting point soluble alloy piece uses four cross-sectional areas of 0.3 mm ² and a melting point of 126 ° C., rosin is used for the flux, and epoxy resin is used for the insulation coating. It was used. A copper wire having a diameter of 0.55 mm was used as the lead wire.
[Comparative Example]
The number of low-melting-point soluble alloy pieces was one, and the same as Example 1 except that the cross-sectional area was approximately 0.3 × 4 mm ² .
[0016]
For each of these examples and comparative examples (each sample number was 10), the sample was immersed in silicon oil at a temperature of 140 ° C. with 5 amperes of direct current supplied, and the time until the interruption of current supply after immersion was measured. In the example, it was within 8 seconds, but in the comparative example, it was 10 to 20 seconds. According to the present invention, it was confirmed that the operation time could be sufficiently shortened.
[0017]
[Example 2]
In FIG. 2, an alumina ceramic plate having a thickness of 0.6 mm is used as the insulating substrate, the membrane electrode is formed by printing and baking silver paste, the outer diameter of the arcuate membrane electrode is φ5.0 mm, and the inner diameter is φ3.8 mm. The outer diameter of the land membrane electrode is φ1.2 mm, the low melting point soluble alloy piece is four pieces with a cross-sectional area of 0.3 mm ² and a melting point of 126 ° C., and an insulating spacer with a thickness of 0.8 mm. A plate was used, rosin was used for the flux, and an epoxy resin was used for the insulation coating. A copper wire having a diameter of 0.55 mm was used as the lead wire.
When the same operation test as described above was performed and the time until the energization was interrupted after immersion was measured, it was within 7 seconds, which was the same operation time as the example.
[0018]
【The invention's effect】
In the substrate-type temperature fuse according to the present invention, the current capacity can be increased for the parallel connection of a plurality of low-melting-point soluble alloy pieces, and the cross-sectional area of the low-melting-point soluble alloy pieces to be connected in parallel is 0. By limiting the thickness to 8 mm ² or less, fusing can be performed quickly.
Therefore, a substrate-type temperature fuse having a large current capacity and a quick operation can be provided.
[Brief description of the drawings]
FIG. 1 is a view showing a substrate type temperature fuse according to claim 1;
FIG. 2 is a view showing a substrate type temperature fuse according to claim 3;
FIG. 3 is a view showing a conventional substrate type temperature fuse.
[Explanation of symbols]
11 Insulating substrate 12 Membrane electrode 121 Arc-shaped membrane electrode 122 Land membrane electrode 13 Lead wire 14 Low melting point soluble alloy piece 15 Flux 16 Insulator 17 Insulating spacer

Claims (4)

This is a thermal fuse in which the low melting point soluble alloy piece is melted by the heat generated by the electrical equipment, and this molten metal is divided by wetting and spreading to the electrode, and a pair of membrane electrodes are provided on an insulating substrate with good thermal conductivity. A plurality of low-melting-point soluble alloy pieces were connected in parallel between the membrane electrodes, a flux was applied to these low-melting-point soluble alloy pieces, and an insulator was covered with the flux-coated low-melting-point soluble alloy pieces. A substrate type temperature fuse characterized by the above. The substrate-type temperature fuse according to claim 1, wherein the interval between the connection points of the low melting point soluble alloy pieces in the other membrane electrode is narrower than the interval between the connection points of the low melting point soluble alloy pieces in the other membrane electrode. 3. A substrate mold according to claim 2, wherein one membrane electrode has an arc shape, the other membrane electrode has a land located in the arc shape, and a plurality of low melting point soluble alloy pieces are connected radially between the two membrane electrodes. Temperature fuse. 4. The substrate type temperature fuse according to claim 1, wherein the cross-sectional area of each low melting point soluble alloy piece is 0.8 mm or less.

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