JPH051144U - Temperature fuse - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To provide a thermal fuse that is easy to install in equipment and has good cutoff characteristics against overcurrent. [Structure] One end A of a leaf spring 1 is joined to a circuit board 3, and the other end of this leaf spring is configured so that a force in the opposite direction is applied to the circuit board. The plate springs are arranged parallel to each other, and the B ends of the leaf springs are joined to the circuit board 3 via the low melting point metal 5. The low melting point metal 5 is melted by the heat generated by the resistor 2 especially against overcurrent. .

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 This invention relates to a thermal fuse. The present invention relates to parts that prevent anomalies in electric and electronic devices, such as parts containing a charger or a heater, malfunctions, and devices that may cause heat generation due to abnormal conditions around the device.

[0002]

[Prior Art]

 As shown in FIG. 6, a conventional thermal fuse has a structure in which a low melting point metal 7 is sealed in a ceramic case 6 and terminals 8 and 9 are taken out. This thermal fuse cannot be attached to the circuit board together with other electronic components. This is because the soldering is usually used to attach the components, and the low melting point alloy will melt at the temperature of the solder.

Therefore, the thermal fuse must be installed elsewhere or at a distance from the circuit board. Therefore, it has a drawback that it requires a large space for the equipment and cannot meet the recent demand for miniaturization.

[0004]

[Problems to be solved by the device]

 The present invention has been proposed in order to improve the above-mentioned drawbacks, and its purpose is to integrate a temperature fuse that prevents abnormalities of electrical and electronic equipment in advance with a circuit board so that it can be easily attached to the equipment. The purpose of the present invention is to provide a thermal fuse that has a good cutoff characteristic against overcurrent.

[0005]

[Means for Solving the Problems]

 According to the present invention, one end of a conductive leaf spring is joined to a circuit board, and the other end is joined to a low melting point metal provided on the circuit board. SUMMARY OF THE INVENTION A thermal fuse characterized in that a resistor connected to a circuit is disposed parallel to the direction, and the leaf spring has a restoring force in the direction opposite to the circuit board. Is.

[0006]

[Action]

 The thermal fuse of the present invention cuts off the circuit when an overcurrent flows or an exothermic ignition occurs due to an abnormal condition of equipment or parts by melting the low melting point metal and removing the leaf spring from the connection terminal. In particular, in the case of an overcurrent, it has a function of cutting off more quickly due to the resistance of the heating element installed under the leaf spring.

[0007]

【Example】

 Next, an embodiment of the present invention will be described. In the present invention, the following structure is used as a structure for easily mounting the thermal fuse on the circuit board.

The material of the circuit board is not particularly limited, such as a laminated board and a ceramic board. In the circuit board, the thermal fuse of the present invention is mounted on the same circuit board as the normal parts of the equipment.

First, as shown in FIG. 1, the resistor 2 is installed on the circuit board 3 from the terminal α for the leaf spring on the portion of the circuit board where the thermal fuse is attached. The resistor is not limited to a screen printing method or a chip resistance. The resistance value is calculated from the circuit design and the amount of heat generated. Reference numeral 4 indicates a wiring pattern.

Next, the leaf spring 1 is processed into the shape shown in FIG. 2, and as shown in FIG. 3, the A end is connected to the α point on the circuit board 3 by a conventional joining method such as soldering. Point β is the connection point with the circuit of resistor 2. FIG. 3 shows a state in which a leaf spring is attached on the circuit board.

The material of the leaf spring has a high electric conductivity and a spring property. For example, phosphor bronze, beryllium copper, etc. are not particularly limited. Next, the B end of the leaf spring is joined to the γ point of the circuit board 3 with the low melting point metal 5 after attaching other parts of the circuit board. As a result, it was assembled as a thermal fuse. The low melting point metal is an alloy having a high melting point of 50 to 300 ° C. and high electrical conductivity. In general, Sn-Pb, Sn-Pb-Bi, etc. are used, but the composition and elements are not particularly limited.

FIG. 4 shows the shape of the assembled thermal fuse. In this thermal fuse, the low melting point metal 5 melts due to overcurrent or temperature rise, and the circuit is cut off. In particular, at the time of overcurrent, the resistor 2 installed under the leaf spring will generate heat and the circuit will be cut off quickly. Fig. 5 shows the appearance of the thermal fuse that has been cut off.

In manufacturing, first, a circuit was formed on a glass epoxy laminate, and a chip resistor was attached to a portion to which a temperature fuse was attached, and the resistance value was 100Ω. Next, phosphor bronze was used as a leaf spring, one end was connected with solder, and the other end was fixed with a low melting point metal (Sn-Pb-Bi alloy) having a melting point of 97 ° C. The leaf spring 1 has a width of 5 mm and a length of 10 mm at the joint with the circuit board and 30 mm at the non-joint portion. This leaf spring has a blocking direction, that is, a reaction force to the side opposite to the circuit board, and is fixed so as to block if the low melting point metal 5 melts. The low melting point metal and the leaf spring were joined after the circuits other than the thermal fuse were manufactured.

Next, an electric current was passed through the temperature fuse of the circuit board produced, a thermocouple was attached around the temperature fuse, and the temperature was gradually raised by placing it in an oven. The current flowing through the thermal fuse and the temperature at that time were measured, and the temperature at which the circuit was interrupted was determined. As a result, it was confirmed that the circuit was interrupted within ± 1 ° C and that it was operating correctly as a thermal fuse. It was In addition, it was confirmed that an overcurrent of 100 A was applied to the temperature fuse in order to examine the overcurrent interruption characteristics, and the interruption was instantaneous.

[0015]

[Effect of the device]

 As described above, according to the present invention, a thermal fuse for an electric / electronic device, which is integrated with a circuit board, can be easily attached to the device, and can be accurately cut off, can be obtained. In particular, it has the effect of accurately cutting off overcurrent.

[Brief description of drawings]

FIG. 1 shows a top view of a circuit board to which a thermal fuse is attached.

FIG. 2 shows a shape of a leaf spring used in the present invention, (a) showing a front view and (b) showing a side view.

FIG. 3 shows a state in which a leaf spring is attached to a circuit board.

FIG. 4 shows a state set as a thermal fuse.

FIG. 5 shows a state in which a thermal fuse is cut off.

FIG. 6 shows a conventional thermal fuse.

[Explanation of symbols]

 1 leaf spring 2 resistor 3 circuit board 4 wiring pattern 5 low melting point metal 6 insulating case 7 low melting point metal 8,9 terminal

Claims (1)

[Claim 1] One end of a conductive leaf spring is joined to a circuit board, and the other end is joined to a low melting point metal provided on the circuit board. A thermal fuse characterized in that a resistor connected to a circuit is arranged parallel to the vertical direction, and the leaf spring has a restoring force in a direction opposite to the circuit board.