JPH0221088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal protector.

As shown in FIG. 6, a conventional thermal protector includes a fixed electrode 2 in a glass container 1, and
It housed a pair of electrodes in which a movable electrode 5 consisting of an electrode lead 4 having a thermally responsive element plate 3 made of trimetal or the like was placed facing each other, and the thermally responsive element plate 3 was welded to the electrode lead 4. In the same figure, 6 and 7 indicate contacts, and 8 indicates a glass bead.

However, in a thermal protector having such a structure, since the thermally responsive element plate 3 and the electrode lead 4 are fixedly connected by welding, self-heating of the thermally responsive element plate 3 occurs when electricity is applied. The temperature at which the plate 3 separates from the fixed electrode 2, ie, the opening operation temperature, becomes lower than the set opening operation temperature. For this reason, the upper limit of the rated current is kept low, resulting in the inconvenience of limited applications and accuracy problems such as the thermally responsive element plate 3 opening before the set opening operation temperature is reached. There was a problem that caused variations.

Further, in the above-mentioned thermal protector, the welded portion of the extremely thin thermally responsive element plate 3 and the electrode lead 4 becomes weak due to welding. Therefore, when the thermally-responsive element plate 3 is repeatedly reversed and returned (contact opening/closing operation), the welded portion becomes the opening/closing fulcrum, which may cause cracks or welding to occur in the welded portion, reducing the durability of the contact opening/closing. There was a problem of damage. The actual lifespan level based on this structure is the average
10,000 times, and the minimum was about 6,000 times.

The present invention was made in view of these problems, and aims to extend the upper limit of the rated current to expand the range of applications, eliminate variations in the set open operating temperature to improve quality, and improve the quality of the thermally responsive element board. The present invention provides a thermal protector that can extend its life by improving its durability.

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B show a front view and a side view of a thermal protector that is an embodiment of the present invention. As shown in Figures A and B, this thermal protector has a metal plate attached to the back surface of the thermally responsive element plate 3 of the movable electrode 9, which is located opposite to the fixed electrode 2 with the contact point 6 welded to the tip. An elastic piece 10 is provided, one end of the metal elastic piece and one end of the thermally responsive element plate 3 are fixed together with the contact 7 by welding, and the other end of the thermally responsive element plate 3 is attached to the metal elastic piece 10. A container 1 such as a glass container 1 is placed in the space 16 of the concave holding part 11 integrated with the assembly structure to serve as a free end.
It is stored inside. The container 1 is filled with an inert gas and its ends are sealed.

Details of an example of the above assembly structure will be explained with reference to FIGS. 2A and 2B. As shown in Figure A, the metal elastic piece 10 has a thickness of 0.08 to 0.12 mm, and consists of a narrow inverted part 10a and a wider part 10b, which is connected to the electrode lead 4. Weld to. The metal elastic piece 10 is preferably made of a material having spring properties and good conductivity, such as phosphor bronze. In addition, as shown in FIG.
One end of the thermally responsive element plate 3 made of 0.1 mm trimetal is welded together with the contacts 7. Metal elastic piece 10
A holding plate 12 having a stepped portion 12a made of a material with good weldability such as an iron alloy such as stainless steel with a thickness of 0.2 mm is attached to the wide portion 10b of the elastic metal piece 10.
The concave space formed between and the stepped portion 12a = 0.15 to 0.25
The other end of the thermally responsive element plate 3 is positioned in the space 16 of the concave holding portion 11 having a diameter of mm, and is welded and fixed as a free end to be integrated. Therefore, since the thermally responsive element plate 3 does not form an electric path, it does not self-heat.

Furthermore, other examples of the above assembly structure are shown in FIGS. 3A and 3B.
Explain with reference to. In this case, the metal elastic piece 13
A step 13c is also provided on the electrode lead 4, and the step 14a of the holding plate 14 is placed along this step, and the metal elastic piece 13 and one end of the holding plate 14 are welded and fixed to the electrode lead 4 to be integrated. As a result, a concave holding portion 15 is formed between the metal elastic piece 13 and the holding plate 14. Then, the other end of the thermally responsive element plate 3 is attached to the concave holding portion 15.
The free end is located in the space 17 of the free end. Therefore, in this case as well, the thermally responsive element plate 3 does not form an electric path and does not self-heat.

In the case of FIGS. 2A and 2B, the thickness of the retaining plate 12 is about twice as thick as that of the metal elastic piece 10, so that the corners are not easily folded during the bending process to form the step. Since it is difficult to form a perfectly right angle and the result is a slightly rounded shape, a slight depth is formed at the point where the surface of the elastic metal piece 10 and the surface of the holding plate 12 intersect within the concave holding portion 11. Grooves are likely to form,
There is a risk that the other end of the thermally responsive element plate 3 may get stuck here and interfere with the reversing operation of the element plate, so consideration must be taken to prevent this from happening. In the case of A and B, even if the thin elastic metal piece 13 is bent to provide the stepped portion 13c, the thickness is still small.
The angles of the corners are almost completely right angles, and therefore, in the space 17 of the concave holding part 15, the surface of the metal elastic piece 13 and the surface of the holding plate 14 are almost perpendicular, so that the groove is not formed. As a result, there is an advantage that the above considerations are not necessary.

Next, the reversal operation of the movable electrode 9 in the thermal protector having the configuration shown in FIGS. 1A and 1B will be described.

The heat-responsive element plate 3 reverses its operation from the state shown in FIGS. 1A and 1B as the ambient temperature rises or as the current (self-heating) in the metal elastic piece 10 increases, due to the conduction heat. However, at this time, since its free end is supported by the concave holding part 11, it is possible to perform a reversal operation together with the metal elastic piece 10, and the contact 7 of the movable electrode 9 is separated from the contact 6 of the fixed electrode 2. , the contacts become open (see Figure 4).

In contrast, in the configuration shown in FIGS. 1A and 1B, if the concave holding portion 11 was not provided, the thermally responsive element plate 3
Even if it tries to perform a reversal operation, the free end of the thermally responsive element plate 3 escapes, and as a result, the contact 7 of the movable electrode 9 remains in contact with the contact 6 of the fixed electrode 2, and the contact is opened. As a result, the reversal operation is not performed (see FIG. 5).

According to the thermal protector of the embodiment of the present invention,
Unlike the conventional method, the metal elastic piece 10 is welded and fixed to the electrode lead 4 instead of the thermally responsive element plate 3 being welded to the electrode lead 4, so the amount of heat conducted to the thermally responsive element plate 3 when energized is greatly reduced. This makes it possible to normalize the set opening operating temperature and time, and also to increase the rated current, thereby expanding the range of applications. Furthermore, the fulcrum of the movable electrode 9 is the metal elastic piece 1.
0, the load on opening and closing the thermally responsive element plate 3 is significantly reduced, and the occurrence of cracks and welding failures in the thermally responsive element plate 3 due to variations in welding conditions can be completely eliminated, thus improving durability. It is possible to achieve a significant improvement in

According to experiments, the thermal protector of the above example has a lifespan of 20,000 cycles on average, and a minimum of 20,000 cycles.
It was confirmed that the durability was 12,000 times, which is twice as long as the conventional model. It was also confirmed that the rated current of this thermal protector was twice that of the conventional one.

As explained above, in the thermal protector of the present invention, since no current flows through the thermally responsive element plate, self-heating of the thermally responsive element plate does not occur, and only conductive heat is generated, the set opening operating temperature is reduced. Therefore, the rated current can be increased to expand the range of applications, and the accuracy can be improved by eliminating variations in the set opening operating temperature and time. Furthermore, in this thermal protector, since there is no welded part at the opening/closing fulcrum of the thermally responsive element plate, the durability of the thermally responsive element plate can be improved and its life can be significantly extended.

[Brief explanation of drawings]

FIGS. 1A and 1B are a partially cutaway front view and a side view of a thermal protector according to an embodiment of the present invention,
Figures 2A and B are a front view and a top view of an example of an assembled structure, Figures 3A and B are a front view and a top view of another example of an assembled structure, and Figure 4 shows the reverse operation state of the thermal protector. FIG. 5 is a diagram for explaining the disadvantages of a thermal protector without a concave holding portion, and FIG. 6 is a partially cutaway front view of a conventional thermal protector. DESCRIPTION OF SYMBOLS 1... Container, 2... Fixed electrode, 3... Thermal response element plate, 4... Electrode lead, 5... Movable electrode, 6,
7...Contact, 10, 13...Metal elastic piece, 11,
15... Concave holding part, 12, 14... Holding plate, 1
6, 17... Space portion of the concave holding portion.

Claims (1)

[Claims] 1. A metal elastic piece is provided on the back surface of the thermally responsive element plate of the movable electrode located opposite to the fixed electrode along the thermally responsive element plate, and one end of the metal elastic piece and one end of the thermally responsive element plate are provided. and the other end of the thermally responsive element plate is positioned in the space of the concave holding part integrated with the metal elastic piece to form a free end, and the assembled structure is housed in a container. A thermal protector with special features.