JPH07220597A - Circuit protective element - Google Patents

Abstract

PURPOSE:To eliminate unevenness in respective parts, and disconnect a current of a specified or larger value surely when it flows through a heating resistor by providing a flat surface part of the heating resistor and a flat part of a fuse element on a base. CONSTITUTION:A heating resistor 2 is a chip resistor of an almost rectangular flat plate to generate hear as current flows, and one flat surface part is provided at a specified position of a base 1 by high-temperature soldering. A fuse element 3 is formed of low melting point alloy or the like as an almost rectangular flat plate to be fused at a specified or higher temperature, and a flat surface part is provided at a specified position of the base 1 by low temperature soldering. A length of a conductive pattern 6 between the heating resistor 2 and the fuse element 3 is set in such a way that the fuse element 3 is fused by heat transmitted from the heating resistor 2 through the conductive pattern 6 before the heating resistor 2 is broken.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit protection element for cutting off an electric current and protecting the electronic circuit when an abnormal current occurs in the electronic circuit.

[0002]

2. Description of the Related Art An electronic circuit device using an AC power supply or a DC power supply may cause noise on the power supply line, destruction of electronic components due to application of lightning surge, and destruction of the electronic components due to the life of the electronic components. , Its effects appear in various ways. For example, in an electronic circuit in which a large number of electronic parts are arranged on a printed circuit board, when the current value exceeds a normal value and becomes large, the current fuse is blown in an instant, or the electronic part heats up abnormally Was sometimes scorched.

As a countermeasure against this, a heating resistor 11 and a thermal fuse 12 as shown in FIGS. 3 and 4 are put in series in the line, and the covering portions thereof are closely adhered to each other to protect the electronic circuit. . When a current flows through the heating resistor 11, the heating resistor 11 depends on the magnitude of the current.
When the heat is generated and a current more than a predetermined value flows, the thermal fuse 12 is melted before the heat generating resistor 11 is cut.

[0004]

However, in the above-mentioned one, the heat generating resistor 11 and the thermal fuse 12 are fixed to the board by soldering the ends of the lead wire exposed from both ends of the heat generating resistor 11 and the temperature fuse 12, respectively. 11 and thermal fuse
The position of 12 is likely to vary, and the heating resistor 11 and the thermal fuse 12 are easily separated from each other. If the heating resistor 11 and the thermal fuse 12 are separated from each other without being in close contact with each other, a malfunction may occur. In order to solve this, it is conceivable to bond the heat generating resistor 11 and the thermal fuse 12 to each other, but there are problems such as poor workability and cost because the bonding process increases.

The present invention has been made in view of the above points, and an object of the present invention is to make the variation of individual parts extremely small, and to make sure that when a current more than a predetermined value flows through the heating resistor. It is to provide a circuit protection element for shutting off the power.

[0006]

In order to achieve the above-mentioned object, the circuit protection element according to claim 1 comprises a substrate having a predetermined outer contour and a flat plate-shaped flat portion provided on the substrate. Heat generation resistance that generates heat when a current flows, a fusible body that is flat and has its flat surface provided on the substrate and that melts when the temperature exceeds a predetermined value, and a heat generation resistance and a fusible body in series. A conductive pattern is printed and printed on the substrate so as to be connected.

The circuit protection element according to a second aspect of the present invention has a structure in which lead terminals are provided on both ends of a conductive pattern that is connected in series so as to include a heating resistor and a fusible element on the substrate of the first aspect. There is.

According to a third aspect of the circuit protection element, the heat generating resistor according to the first or second aspect is provided on the substrate by printing.

Further, the circuit protection element according to claim 4 has a structure in which a resin is attached to the substrate according to any one of claims 1 to 3 so as to cover at least the heating resistor and the fusible body.

[0010]

According to the structure of the first aspect, since the flat portion of the heating resistor and the flat portion of the fusible body are provided on the substrate, the heating resistor and the fusible body are less likely to be displaced from their normal positions.

According to the second aspect of the invention, when the lead terminals are provided in the vacant space of the substrate, the miniaturization of the whole can be realized.

According to the third aspect of the invention, the workability when the heating resistor is provided on the substrate is good, and the heating resistor does not deviate from the normal position.

According to the fourth aspect of the present invention, the heat generating resistance and the fusible body are protected by the resin, and further less likely to be displaced from the normal position.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

This circuit protection element consists of a substrate 1 and a heating resistor.
2, fusible body 3, lead terminals 4, 5 and conductive pattern 6
And is configured.

The substrate 1 is made of paper phenol, ceramic or the like in a substantially rectangular shape, and has a heating resistor 2, a fusible body 3, and lead terminals 4 and 5 electrically connected to one end surface thereof so as to be connected in series. Pattern 6 is printed and wired.

The heating resistor 2 is a chip resistor in the shape of a substantially rectangular flat plate that generates heat when an electric current flows, and one plane portion is a substrate.
It is provided at a predetermined location of 1 by high temperature solder. Soluble body
The reference numeral 3 is formed in a substantially rectangular flat plate shape by a low melting point alloy or the like so as to be fused when the temperature exceeds a predetermined value, and one flat surface portion is provided at a predetermined position on the substrate 1 by low temperature soldering. The reason why the low temperature solder is used when the fusible body 3 is provided on the substrate 1 is that the fusible body 3 is melted and cut when the high temperature solder is used. The length of the conductive pattern 6 between the heating resistor 2 and the fusible element 3 is set so that the fusible element 3 is melted by the heat conducted from the heating resistor 2 through the conductive pattern 6 before the heating resistor 2 is cut off. It has been decided on the length. The lead terminals 4 and 5 are formed in a long plate shape, and the tip side is the substrate.
A flat surface of the base end is provided on the substrate 1 by high-temperature solder so as to project from 1.

Next, the operation of this embodiment will be described with reference to FIG. When a current flows through the heating resistors 2 and the fusible body 3 via the lead terminals 4 and 5, the heating resistors 2 generate heat according to the magnitude of the current. The circuit protection element does not break if the input current is the rated input, but the fusible body 3 breaks before the heating resistor 2 when the input current increases.

As described above, in this embodiment, one flat surface portion of the heating resistor 2 is provided on the substrate 1 by high temperature solder, and one flat surface portion of the fusible body 3 is provided on the substrate 1 by low temperature solder.
The heating resistance 2 and the fusible body 3 are less likely to be displaced from their normal positions. Therefore, in the present embodiment, the fusible body 3 melts down when a current of a predetermined value or more flows through the heating resistor 2, so that the current can be reliably cut off. Further, in this embodiment, since the lead terminals 4 and 5 are provided in the vacant space of the substrate 1, it is possible to downsize the whole shape of the circuit protection element.
It does not take up a lot of space when connected to other electronic circuits with lead terminals 4 and 5.

In this embodiment, the heating resistor 2 and the fusible element are used.
Although the conductive pattern 6 is interposed between the
The soluble body 3 may be closely attached.

Further, in the present embodiment, the fusible body 3 is formed of a low melting point alloy or the like and the periphery thereof is exposed, but the periphery may be covered with an insulating material to form a thermal fuse.

Further, in the present embodiment, the heating resistor 2 is a chip resistor, but another one may be used. For example, when the heating resistor 2 is a resistor (thick film resistor, thin film resistor, etc.) provided on the substrate 1 by printing, the workability when the heating resistor 2 is provided on the substrate 1 can be improved, and the heating resistor 2 can be It does not deviate from the normal position from board 1. As the heat generating resistor 2, a thick film resistor and a thin film resistor may be selectively used according to the magnitude of the input current. In addition to this, heat resistance 2
When the heat resistance is the same as in the conventional example, when the fusible body 3 malfunctions and the heat resistance 2 cuts in the heat resistance open area shown in Fig. 2, a sound is generated and the user feels a sense of crisis. Since it may be given, it is preferably not used.

Further, in this embodiment, the respective members provided on the substrate 1 are exposed, but the lead terminals 4 and 5 may be removed, and a resin such as an epoxy resin may be attached to the substrate 1. . In this case, since the heat generating resistance 2 and the fusible body 3 are protected by the resin, damage due to external factors can be prevented, and the heat generating resistance 2 and the fusible body 3 are further less likely to be displaced from their normal positions by the resin. Further, even if the internal members (heating resistance 2, fusible body 3) are broken due to impact or large current flow, it is safe because it does not scatter.

[0024]

In the circuit protection element according to the first aspect of the present invention, since the flat portion of the heat generating resistor and the flat portion of the fusible body are provided on the substrate, the heat generating resistor and the fusible body are less likely to be displaced from their normal positions, and as a result, heat is generated. When a current more than a predetermined value flows through the resistor, the current can be surely cut off.

The circuit protection device according to a second aspect is the first aspect.
In addition to the effects described above, when the lead terminals are provided in the vacant space of the substrate, the miniaturization of the whole can be realized.

The circuit protection device according to claim 3 is the circuit protection device according to claim 1.
Alternatively, in addition to the effect described in 2, it is possible to improve workability when the heating resistor is provided on the substrate. Further, since the heat generating resistance does not deviate from the normal position, it is possible to more reliably interrupt the current when a current more than a predetermined value flows through the heat generating resistance.

The circuit protection device according to claim 4 is the circuit protection device according to claim 1.
In addition to the effect described in any one of 1 to 3, since the heat generation resistance and the fusible body are protected by the resin, damage due to external factors can be prevented. Further, since the heat generating resistor and the fusible body are more difficult to be displaced from the normal position by the resin, the current can be more surely cut off when a current more than a predetermined value flows through the heat generating resistor.

[Brief description of drawings]

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

FIG. 2 is a graph showing a characteristic of an operation according to the input current.

FIG. 3 is a perspective view of a conventional example.

FIG. 4 is a circuit diagram thereof.

[Explanation of symbols]

 1 Board 2 Heat resistance 3 Fusible body 4 Lead terminal 5 Lead terminal 6 Conductive pattern

Claims (4)

[Claims] 1. A substrate having a predetermined contour, a flat plate-shaped flat portion provided on the substrate, and a heating resistor that generates heat when an electric current flows, and a flat plate-shaped flat portion on the substrate. What is provided is a circuit protection element, comprising a fusible body that melts and cuts when a temperature rises above a predetermined level, and a conductive pattern printed and printed on a substrate so that a heating resistor and the fusible body are connected in series. 2. The circuit protection element according to claim 1, wherein lead terminals are provided at both ends of a conductive pattern that is connected in series on the substrate so as to include a heating resistor and a fusible body. 3. The circuit protection element according to claim 1, wherein the heat generating resistor is provided on the substrate by printing. 4. The circuit protection element according to claim 1, wherein the substrate is covered with a resin so as to cover at least the heat generating resistance and the fusible body.