JP3089993B2 - Thermal protector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a normally closed contact type self-recovering thermal protector.

[0002]

2. Description of the Related Art Such a thermal protector comprises a movable electrode having a movable element such as a direct heat type or indirectly heated bimetal or the like as a movable piece, and a fixed electrode constituting a normally closed contact type switch together with the movable electrode. And protects the electrical device by being connected to the electrical device. In other words, the thermal protector connected to the power supply circuit of the electrical equipment opens the switch contacts by the bending action of the thermal element only when excessive current flows in the electrical equipment or when the ambient temperature becomes abnormally high. Then, the power supply to the electric device is cut off. Then, the switch contact that has automatically returned due to the temperature drop due to the cutoff of the power supply restarts the power supply, which not only helps to prevent danger but also allows the electric device to always operate in a predetermined temperature range. In addition, it is possible to notify an abnormality of the electric device.

[0003]

However, if such a thermal protector is used for a long period of time, the electrode components will be deteriorated due to metal fatigue and contact wear, resulting in an initial switch operation. Does not work satisfactorily. In particular, when the use is continued after the warranty period, there is a danger that the switch contacts may be fused to each other to cause damage to the electric device.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a thermal protector that has a function of interrupting an excessive current even when the switch contacts are fused. Things.

[0005]

A thermal protector according to the present invention comprises a fixed electrode having a fixed contact at an end, a movable electrode having a movable contact at an end, which is deformed by heating and comes into contact with and separates from the fixed electrode. In a thermal protector with
In the fixed electrode, a plurality of electrode plates are fixed to each other via a soluble metal portion in a length direction, and at least one fixed side end of the electrode plate fixed to each other is formed of the soluble metal portion. It has a configuration provided so as to protrude beyond the linear axis connecting the midpoints of both ends to the other electrode plate side.

[0006]

In the present invention, the fixed electrode is composed of a plurality of electrode plates and is fixed to each other in the longitudinal direction via a soluble metal portion, and this soluble metal portion serves as a thermal fuse. That is, if an excessive current flows while the contacts are fused, the movable electrode will rise in temperature and bend, but since the movable electrode is fused to the fixed electrode at the contact point, the excessive current will flow. Keeps flowing. For this reason, the movable electrode further generates heat but cannot bend, and accumulates strain. Since a part of the heat generated by the movable electrode is conducted to the fixed electrode side through the contact, the fixed electrode eventually melts at the soluble metal portion. Since the movable electrode at the time of fusing instantaneously releases the accumulated strain force and is greatly displaced,
The fusing is achieved instantaneously and reliably (see FIG. 9). In addition, since at least one fixed end of the mutually fixed electrode plates protrudes toward the other electrode plate beyond the linear axis connecting the midpoints of both ends of the fusible metal portion, it is fixed. The bending strength of the electrode can be increased, and the bending of the fixed electrode caused by the inversion and return movement for a long time can be prevented.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A normally closed contact type self-recovering thermal protector according to an embodiment of the present invention shown in FIG. 4 comprises a fixed electrode 1 made of an alloy of copper and nickel having a fixed contact 2 made of silver at one end.
And a thermally responsive element 4 which has a movable contact 3 at one end, is deformed by heating, and comes into contact with and separates from the fixed electrode 1. The fixed electrode 1 and the thermally responsive element 4 are provided facing each other such that the movable contact 3 of the thermally responsive element 4 is located opposite to the fixed contact 2 of the fixed electrode 1. The other end of the fixed electrode 1 is fixed to one end of the fixed electrode support plate 6, and the other end of the thermoresponsive element 4 is fixed to one end of the movable electrode support plate 5 by welding. The fixed electrode support plate 6 and the movable electrode support plate 5 are fixedly held by a resin block 7 and a filler 9, respectively. Fixed electrode support plate 6 and movable electrode support plate 5
Are connected to the external lead wires 8 in the resin block 7 by welding. In addition, 10 shows a case.

As shown in FIG. 1, the fixed electrode 1 has two electrode plates 1a and 1b fixed to each other in a longitudinal direction via a soluble metal portion 11 made of, for example, solder. Further, at least one of the fixed side ends 12 of the mutually fixed electrode plates 1a and 1b crosses a straight axis (straight line A ₁ -A ₂ ) connecting the midpoints of both ends of the fusible metal portion 11, and the other end. Are protrudingly provided on the side of the electrode plate.

For comparison, the normally closed contact type self-recovering type thermal protector (hereinafter referred to as the product A of the present invention) and the electrode plates 1 fixed to each other as shown in FIG.
The fixed electrode 3a, 13b has a configuration in which the fixed-side end 12 does not protrude beyond the linear axis (straight line A ₁ -A ₂ ) connecting the midpoints of both ends of the fusible metal portion 11 to the other electrode plate side. 1
3, that is, a thermal protector (hereinafter referred to as a comparative product) in which, for example, a linear soluble metal portion 11 was formed on the fixed electrode 13 was produced. The material of the soluble metal part 11 was solder. As shown in FIGS. 2 and 3, similarly to the above, the fixed-side end portion 12 exceeds the linear axis (straight line A ₁ -A ₂ ) connecting the midpoints of both ends of the fusible metal portion 11 to the other electrode. The fixed electrode 1 protruding toward the plate side, ie,
A thermal protector in which the soluble metal portion 11 shown in FIG. 2 has a non-linear shape, for example, a saw shape (hereinafter, referred to as the present invention B), and a curved shape (hereinafter, referred to as the present invention C) shown in FIG. And examined.

[0010] The maximum rated voltage and current are applied to such a thermal protector, that is, 55,000 times the specified number of times.
After performing the inversion and return movements twice, the return temperature and the inversion temperature of each sample under no load were measured. The number of samples is n
= 100.

As a result, in the comparison product, 17 cases where the reversal temperature or the return temperature showed a temperature deviation of 10% to 20% from each initial value, and 5 cases where the temperature deviation exceeded 20% were confirmed. Was done. On the other hand, in the products A to C of the present invention, the temperature deviation was all within 3%, and it was confirmed that the fluctuation of the temperature characteristics was extremely small. As a result of analyzing the above-mentioned comparative product having a temperature deviation, the fixed electrode bends from the soluble metal part 11 as shown in FIG.
It was found that the contact portion was considerably deviated from the initial position (indicated by the broken line in FIG. 7). This is considered to have adversely affected the return temperature or the inversion temperature accuracy.

Since the soluble metal portion 11 made of solder or the like is softer than a fixed electrode made of an alloy of copper and nickel, as the reversal return operation is repeated for a long time, as shown in FIG.
As shown in (1), the fixed electrode 13 gradually bends around the soluble metal portion 11 due to the spring property of the thermally responsive element 4 and shifts from the initial position. When the configuration of the fixed electrode 1 of the product A of the present invention described above is compared with the fixed electrode 13 of the comparative product as shown in FIG. 8, the comparative product has a linear axis (straight line A ₁ −
The soluble metal portion 11 is formed on the entire surface of A ₂ ), and the fixed electrode is easily bent from this portion. On the other hand, the product A of the present invention has a soluble metal part 1 on a straight axis (straight line A ₁ -A ₂ ).
1 and a part of the electrode plate, the fixed electrode 13
Can be significantly improved in bending strength. as a result,
It is possible to prevent the fixed electrode 1 from being bent due to the long-time inversion and return movement, thereby making it possible to extremely reduce the return temperature and the change in the inversion temperature. The products B to C of the present invention
In this case, the same effect as that of the product A of the present invention can be obtained.

[0013] Next, after performing the reversing and returning movement a specified number of times 5000 times at the maximum rated voltage and current in the thermal protector of the above embodiment, the movable contact and the fixed side contact are forcibly welded, and the maximum rated current value is determined. Five times was applied. As a result, for each of the 50 samples, the products A to C of the present invention were all soluble metal part 1
It was confirmed that 1 was melted and the circuit was opened as shown in FIG.

Next, a thermal protector according to another embodiment of the present invention will be described. As shown in FIGS. 5 and 6, a thermal protector of another embodiment of the present invention
The electrode plates 14a, 14b, and 14c have fixed electrodes 14 fixed to each other in the longitudinal direction through a plurality of soluble metal portions 11 made of, for example, solder, as in the above-described embodiment. In addition, at least one fixed end portion 12 of the electrode plates 14a, 14b, 14c of the fixed electrode 14 fixed to each other has a straight axis (straight line A ₁ -A) connecting the midpoints of both ends of the fusible metal portion 11. Beyond ₂ ), it protrudes toward the other electrode plate. The soluble metal portion 11 has a non-linear shape, for example, a rectangular shape, a saw shape, or a curved shape. By combining the soluble metal portions 11 having these shapes, a plurality of, for example, two soluble metal portions 11 are formed on the fixed electrode 14. doing. As shown in FIG. 5, the thermal protector of the present embodiment has the soluble metal portion 11 at two locations as the fixed electrode 14, one having a rectangular shape and the other having a curved shape (hereinafter referred to as product D of the present invention). 6), as shown in FIG. 6, two portions having a soluble metal portion 11, one having a rectangular shape and the other having a saw-like shape (hereinafter referred to as a product E of the present invention). When such a thermal protector was manufactured and measured under exactly the same conditions as described above, good results could be obtained as in the case of the above-described present invention products A to C, and the portion fixed by the soluble metal portion 11 was As the number increases, safety can be further improved.

As is clear from the above results, the present invention
Fixed electrodes 1 and 14 having fixed contacts 2 at the ends and movable contacts 3 at the ends, which are deformed by heating and are fixed.
In a thermal protector provided with a movable electrode 4 and a thermally responsive element 4 which is a movable electrode, a plurality of electrode plates are fixed to each other via a fusible metal portion 11 in a longitudinal direction. At least one of the fixed ends 12 and 15 of the electrode plates fixed to each other exceeds a linear axis (straight line A ₁ -A ₂ ) connecting the midpoints of both ends of the fusible metal portion 11,
Since it is provided so as to protrude toward the other electrode plate side, even if an overcurrent occurs when the contacts are welded at the end of life and remain in a closed state, the soluble metal portion 11
Is blown to be in an open circuit state, and an overcurrent can be instantaneously cut off. In addition, even after a long-time reversal return movement, the return temperature or the reversal temperature hardly changes from the initial characteristic value, and an extremely reliable normally closed contact type self-recovery type thermal protector can be obtained. is there.

[0016]

As described above, according to the thermal protector of the present invention, if the contacts are welded at the end of life or the like and remain in a closed state, an abnormal temperature rise or overcurrent occurs in the electric equipment. Also, the soluble metal part is blown, the fixed electrode can be separated and the circuit can be opened, preventing the temperature rise of the motor and the fluorescent lamp ballast etc., and preventing the danger of ignition of electric equipment etc. it can. In addition, a highly reliable normally closed contact type self-recovering thermal protector that prevents the fixed electrode from being bent due to the reversing and returning movement for a long time, and the return or reversal temperature hardly changes from the initial characteristic value. That can be provided.

[Brief description of the drawings]

FIG. 1 is a front view of a fixed electrode of a thermal protector according to an embodiment of the present invention.

FIG. 2 is a front view of the same fixed electrode.

FIG. 3 is a front view of the same fixed electrode.

FIG. 4 is a partially cutaway front view of the thermal protector.

FIG. 5 is a front view of a fixed electrode of a thermal protector according to another embodiment of the present invention.

FIG. 6 is a front view of the same fixed electrode.

FIG. 7 is a diagram showing the internal structure of the thermal protector after a reversal return movement of the comparative product for a long time.

FIG. 8 is a front view of a fixed electrode of a comparative thermal protector.

FIG. 9 is a view showing the internal structure of the thermal protector after the fixed electrode is blown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 14 Fixed electrode 2 Fixed contact 3 Movable contact 4 Thermal response element 11 Soluble metal part 12 Fixed side end

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01H 37/00-37/56 H01H 85/00-87/00 H01H 11/00-11/06

Claims (4)

(57) [Claims] 1. A thermal protector comprising: a fixed electrode having a fixed contact at an end; and a movable electrode having a movable contact at an end, which is deformed by heating and comes into contact with and separates from the fixed electrode. A plurality of electrode plates are fixed to each other via a soluble metal portion in the length direction, and at least one fixed side end of the mutually fixed electrode plate is a midpoint of both ends of the soluble metal portion. Beyond the linear axis connecting each other,
A thermal protector provided so as to protrude toward the other electrode plate. 2. The thermal protector according to claim 1, wherein the soluble metal portion has a non-linear shape. 3. The thermal protector according to claim 1, wherein the fusible metal portion has a rectangular shape, a saw shape, or a curved shape. 4. The fixed metal electrode is provided with a plurality of fusible metal portions at a plurality of positions, and the fusible metal portions provided at the plurality of positions are formed of any combination of a rectangular shape, a saw shape, and a curved shape. The thermal protector according to claim 1, wherein