JPS6016017Y2 - temperature fuse - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a temperature fuse that interrupts an electrical circuit when the ambient temperature rises to a certain temperature.

Figure 1 shows a general conventional example of a temperature fuse, which is used in a wide range of fields as an overheat prevention device for electrical equipment.
1 is a cylindrical metal case made of copper, 2 is a first lead that is airtightly, electrically and mechanically fixed to one end of the metal case 1 by caulking, etc., and 3 is a metal case sealed with the first lead 2. It is a temperature-sensitive pellet inserted into one end of the inside of 1, and is made of an insulating chemical substance that is solid at room temperature and melts into a liquid when the ambient temperature rises to a certain temperature (operating temperature).

4 is a second lead led out from the other end of the metal case 1; 5 is an insulating bushing made of ceramic or the like that penetrates and seals the second lead 4; and 6 is the inner part of the second lead 4 that protrudes from the bushing 5. This is a fixed contact with a bulge on the tip.

7 is a strong compression spring for closing the circuit, 8 is a star-shaped movable contact as shown in FIG. Compression springs 1° and 11 are push plates, which are inserted into the metal case 1 as follows.

First, the temperature-sensitive pellet 3 is inserted from one open end of the metal case 1, and then the push plate 10, the strong compression spring 7, and the push plate 11 are inserted, and then the peripheral part is pressed against the inner peripheral surface of the metal case 1. The movable contact 8 is press-fitted by sliding.

Thereafter, the weak compression spring 9 is inserted, and then the bushing 5 with the second lead 4 integrated therein is passed through the center of the weak compression spring 9 and inserted.

At this time, the fixed contact 6 presses the movable contact 8 and the strong compression spring 7
is sufficiently strongly compressed, and on the other hand, a weak compression spring 9 having a spring force weaker than that of the strong compression spring 7 is compressed and interposed between the movable contact 8 and the bushing 5.

Then, while maintaining this state, the bushing 5 is fixed to one end portion of the metal case 1 with a screw or the like, and this fixed portion is further sealed with an insulating sealing material 12 such as epoxy resin.

In addition, 13 in FIG. 1 is a protrusion formed by caulking the outer end of the second lead 4 from the bushing 5, and 14 is an insulating tube made of glass or the like fitted into the lead-out portion of the second lead 4. , the protrusion 13 prevents the second lead 4 from moving inward of the metal case 1 after the temperature fuse is activated, and the insulating tube 14 increases the creepage distance between the second lead 4 and the metal case 1 to increase the dielectric strength. It is useful for increasing insulation resistance.

At room temperature in FIG. 1, the temperature-sensitive pellet 3 is solid, and the spring force of the strong compression spring 7 keeps the movable contact 8 in elastic contact with the fixed contact 6. At this time, the temperature fuse is 2-
Current flows through the path 1-8-6-4.

When the ambient temperature rises to the operating temperature of the temperature-sensitive pellet 3, the temperature-sensitive pellet 3 melts and becomes a liquid that flows from between the metal case 1 and the push plate 10, and the strong compression spring 7 expands, causing the spring force to change to the weak compression spring 9. becomes weaker than the spring force of.

Then, the movable contact 8 is pushed toward the temperature-sensitive pellet 3 by the spring force of the weak compression spring 9, and as shown in FIG. 2, the movable contact 8 is separated from the fixed contact 6, and the current path of the temperature fuse is interrupted.

Since the purpose of use of this type of temperature fuse is to prevent danger from excessive temperature rises, the criteria for passing such tests as operation tests, withstand voltage tests, and high-temperature storage tests are strict.

The operation test not only checks to see if the device operates reliably at the indicated operating temperature, but also to ensure that no sparks are generated during operation.

The withstand voltage is related to the separation distance 11 of the movable contact 8 from the fixed contact 6 after operation, and the larger 1□ is, the more desirable it is for improving the withstand voltage.

By the way, in the conventional temperature fuse described above, the movable contact 8 is in frictional engagement with the metal case 1, so the separation speed and separation distance 11 of the movable contact 8 are determined by the balance between the frictional force between these two surfaces and the spring force of the weak compression spring 9. is decided.

Therefore, in order to eliminate the generation of sparks during operation or increase the withstand voltage after operation, it is conceivable to increase the spring force of the weak compression spring 9 or to decrease the frictional force.

However, if the spring force is increased, the spring force of the strong compression spring 7 must be further increased in order to bring the movable contact 8 into sufficiently strong elastic contact with the fixed contact 6 at room temperature.

In this way, when the spring force of each compression spring 7.9 is relatively increased, depending on the material of the temperature-sensitive pellet 3, the compressive stress may reach the limit and the pellet may become soaked, or the temperature-sensitive pellet 3 may become soaked in a high-temperature storage test. The push plate 10 moves due to the viscous flow of the strong compression spring 7.
This is not desirable as it may stretch a little and cause malfunction.

In addition, if the elastic force of the movable contact 8 to the metal case 1 is weakened to reduce the frictional force, the contact resistance between the two will increase and the internal resistance will increase, causing heat generation at room temperature and making the inside of the metal case 1 higher than the ambient temperature. This may cause malfunction.

Another problem with the material is that the movable contact 8 needs to be made of an expensive metal such as a silver-cadmium alloy.Moreover, it is shaped like a star to provide effective spring properties, but this reduces the material utilization rate. They tended to be poor and even more expensive.

In view of the fact that the above-mentioned conventional problems are caused by the movable contact, the present invention provides a temperature fuse that solves all the above-mentioned problems by improving the movable contact.

The present invention will be explained below with reference to examples.

For example, when the present invention is applied to the temperature fuse shown in Fig. 1, the main parts are shown in Figs. 4 and 5. The same reference numerals as in Fig. 1 indicate the same contents as in Fig. 1. , the following movable contact 15 is different.

The movable contact 15 is composed of two disc-shaped contact plates 16 and 17 and one ring 18.

Each contact plate 16, 17 is made of a highly conductive metal such as a copper plate, and each has the same shape and is used as a set of two with the palms facing each other. The tapered surfaces m, , m2 are finished.

Further, the outer diameter d1 of each contact plate 16, 17 is set to be slightly smaller than the inner diameter of the metal case 1.

The ring 18 is in the shape of a C ring as shown in FIG. 7, and is made of a metal such as phosphor bronze that has good conductivity and has some spring properties.

The outer diameter d3 of this ring 18 in its free state (solid line in Figure 7)
is made slightly smaller than the inner diameter of the metal case 1.

What is important is that when the ring 18 in a free state is sandwiched between the opposing tapered surfaces m19m2 of each contact plate 16.17 and the contact plates 16.17 are pressed against each other to bring the palms together, the tapered surfaces m1. The ring 18 and the contact plates 16 and 17 are designed so that m2 pushes the ring 18 apart while holding it in place (the shape shown by the chain line in FIG. 7), and the outer diameter of the ring 18 is made slightly larger than the inner diameter of the metal case 1. .

The movable contact 15 is assembled within the metal case 1.

That is, a three-member set with the ring 18 slightly sandwiched between the contact plates 16 and 17 is inserted between the strong compression spring 7 and the weak compression spring 9.

Then, with the spring force of the strong compression spring 7, each contact plate 16.1
7 is pressed against the fixed contact 6 side, and each contact plate 16, 17 comes into contact with the palms to spread the ring 18, bringing the ring 18 into elastic contact with the inner circumferential surface of the metal case 1 (FIG. 4).

The state shown in FIG. 4 is maintained at room temperature, and the current flows through the paths 2-1-18-18, 17-6-4.

Further, when the ambient temperature becomes higher than the operating temperature, the temperature-sensitive pellet 3 melts, the strong compression spring 7 expands, the contact plates 16 and 17 are opened by the restoring force of the ring 18, and the ring 18 separates from the metal case 1.

At the same time, the weak compression spring 9 pushes out the contact plate 16, 17, and as shown in FIG. 6, the contact plate 16 separates from the fixed contact 6 and the current path is interrupted.

At this time, since the movable contact 15 is released from the metal case 1, the weak compression spring 9 pushes out the movable contact 15 with no resistance, which not only makes it possible to sufficiently increase the speed of separation from the fixed contact 6, but also The separation distance of 1° from the contact point 6 to the contact plate 16 is sufficiently large (12>>11), which prevents generation of sparks during operation and improves withstand voltage after operation.

Further, the spring force of the weak compression spring 9 may be small, and therefore the spring force of the strong compression spring 7 may also be small, so that it is possible to eliminate malfunctions due to soaking of the temperature-sensitive pellet 3 or viscous flow.

Note that the present invention is not limited to the above-mentioned embodiment; for example, at least the contact plate 16 that contacts the fixed contact 6 must be made of a highly conductive metal, while the other contact plate [7] is made of an insulating material. It is also possible to use a plate.

In addition, the contact plate 16 and the weak compression spring 9 and/or the contact plate 1
7 and the strong compression spring 7 may be fixed and integrated.

Alternatively, the contact plates 16, 17 may be provided with recesses into which the compression springs 9, 7 fit.

As explained above, according to the present invention, the opening speed and opening distance of the movable contact can be increased without increasing the spring force of the compression spring, and a temperature fuse with stable operation without spark generation and a high withstand voltage after operation can be achieved. can be provided.

In addition, the contact plate and ring of the movable contact can be made of inexpensive metals such as copper and phosphor bronze, and can be shaped with less waste of material, so the cost of the temperature fuse can be reduced.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of a conventional temperature fuse before and after operation, Figure 3 is an enlarged cross-sectional view taken along line A-A in Figure 1, and Figure 4 is a temperature fuse according to the present invention. 5 is a sectional view taken along line B-B in FIG. 4, FIG. 6 is a sectional view after the operation of FIG. 4, and FIG. 7 is a sectional view of the ring shown in FIG. 4. FIG. 1... Metal case, 3... Temperature-sensitive pellet, 6... Fixed contact, 7, 9... Compression spring, 15... Movable contact, 16.17...
...Contact plate, 18...Ring, m19m2...
...Tapered surface.

Claims (1)

[Scope of utility model registration request] In a temperature fuse, a temperature-sensitive pellet and a fixed contact are arranged facing each other at both ends in a sealed metal case, and a movable contact and a compression spring that presses the movable contact against the fixed contact are arranged in the middle part. The movable contact has an outer diameter smaller than the inner diameter of the metal case, and the periphery of each facing surface is chamfered in a tapered shape, and at least the fixed contact side is made of a highly conductive metal plate.
The contact plate is made up of a pair of contact plates and a highly conductive ring that has an outer diameter smaller than the inner diameter of the metal case in a free state and fits into the tapered surface of the contact plate.The spring force of the compression spring causes each contact plate to come together. A temperature fuse characterized by a tapered surface that expands the ring and brings it into pressure contact with the inner peripheral surface of the metal case.