JPS5816162Y2 - surge absorber - Google Patents

Description

[Detailed description of the invention] This invention has the advantage of suppressing the rise in the limit voltage due to the inductance of the lead wires used in varistors, and at the same time enables automatic solder dipping even for varistors with large element shapes. The present invention provides a surge absorber with

A conventional surge absorber is shown in FIG.

In Fig. 1, 1 is a disk-shaped varistor element mainly made of metal oxide such as zinc oxide, and 2 and 2' (2 o, not shown) are printed on the opposing front and back surfaces of the varistor element 1. The effect of the varistor element 1 can be obtained between the two electrodes 2 and 7 by using a silver electrode, for example.

Button 3 and 3' are lead wires with good conductivity such as copper wire soldered onto electrodes 2 and 2', and one electrical terminal is provided on each of both electrodes 2 and 2'. ing.

Additionally, these surge absorbers are typically insulators (not shown).
The lead wire is coated with only 3°3' electrical terminals left.

Now, the conventional surge absorber is used between the power line t (or between the line and the ground) as shown in Fig. 2, but the lead wire 3 in Fig. 1 is connected to the power line t. For example, if the stray inductance 5 of the lead wire 3 is equal to the varistor 4
This means that they are connected in series.

Therefore, if a surge voltage is applied between the lines and a surge current ■ flows as shown by the arrow, the residual voltage between the lines will be reduced to the varistor 4.
The voltage drop due to the floating inductance 5 is added to the limiting voltage of , and its protective characteristics are degraded.

That is, the voltage drop VL across the stray inductance 5
is VI, = -Ldi/dt (where L is the lead stray inductance, and di/dt is the current change rate of the surge current)
The longer the lead wires 3, 3' in FIG. 1 and the larger the di/dt, the greater the voltage drop across the floating inductance 5.

In particular, for a current having a rise on the order of 1 ion (nanoseconds) included in noise, the current limit voltage may be twice as high as the original limit voltage of the varistor 4 in some cases.

This situation is shown in Figure 3, where the solid line characteristic A is the original limiting voltage characteristic of the varistor 4, and the dotted line % characteristic B is the limiting voltage characteristic of the surge absorber including the lead wires 3 and 3'. be.

The difference in characteristics B-A is the amount of voltage drop caused by the stray inductance 5.

With the twisted lead wire structure shown in Figure 1, heavy devices cannot be held in place by the clamping force of the two lead wires 3 and 3', and automatic solder dipping is not possible. It had the disadvantage of extremely poor workability.

The present invention proposes a surge absorber that solves the above two problems, namely, the deterioration of protection characteristics due to voltage drop in the lead wire, and the problem of not being able to apply automatic solder dipping when the element weight is too large. It is something.

Hereinafter, the basic structure of the surge absorber according to the present invention will be explained with reference to FIG. 4.

In FIG. 4, 6 is a disk-shaped varistor element mainly made of metal oxide such as zinc oxide, and electrodes such as silver electrodes are provided on both the front and back surfaces of this varistor element 6. , 7'(7' is not shown).

8a, 88' and 8b, 8b' are lead wires 3 in FIG.
, 3', and has a total of four electrical terminals.

That is, the lead wires 8 b and 8 b' are formed into a U-shape and soldered onto the electrode γ.
Two terminals are drawn out in parallel in the same direction.

The twisted lead wires 8a and 813' are also lead wires 8b,
It has the same shape as 8b', is soldered onto the electrode 1', and its two terminals are drawn out in the same direction in parallel with the two terminals of the lead wires 8b and 8b'.

Then, the normal lead wires 8a*8a and 8b, 8
The surge absorber is completed by coating the electrical terminal portion b' with an insulating material.

When a surge absorber having such a lead structure is connected to a power supply line, its equivalent circuit becomes as shown in FIG.

9a, 9dk and 9b in FIG. 9b male power line, 10 is varistor, 11a, 11a' and 1
1 b and 11 b' are stray inductances of the lead wires 8at8a' and 8b, respectively.

That is, when the surge current I flows, a voltage drop occurs across the floating inductances 11b and 11b', but a voltage drop does not occur across the floating inductances 11a and 11a'.

Therefore, between the lead wires 8a and 8a', the varistor 10
Only the original limited voltage appears, and characteristic A shown in FIG. 3 is obtained.

Here, as mentioned above, the two U-shaped lead wires 8
Since the varistor element 6 is sandwiched between the lead wires Ba5is' and 8b and 8b', the rate at which the varistor element 6 falls off from the lead wires Ba5is' and 8b and 8b' is reduced, and the automatic soldering process is reduced. Dipping is also possible.

However, in the above configuration, the lead wire 8a.

Although the strength of sandwiching the varistor element 6 between 8a', 8b and 8b' is improved to some extent, it cannot be said to be sufficient.

Therefore, embodiments of the present invention that further improve this strength are shown in Figs.
The portions to be soldered onto the electrodes T 2 and 13 are curved in a V-shape, W-shape, etc., and in this case automatic solder dipping of devices with a larger weight becomes possible.

Furthermore, another embodiment of the present invention is shown in FIG. It is bent and then folded back again so as to be on the same line as the varistor element 6 surface, so that the pitch between the terminal parts of the two straight lines 14 and 14' in the element thickness direction is made wider than the thickness of the varistor element 6.

In this embodiment, even if a circuit voltage and a limiting voltage at the time of surge current inflow are applied between the lead wires 14 and 14', a sufficient insulation distance between the lead wires 14 and 14' is maintained, so the varistor It can bring out its original effect.

In other words, if the insulation distance is not sufficient, leakage current increases and discharge occurs between the IJ and D wires, causing problems in which the varistor's original effects cannot be exhibited.

In the embodiment shown in FIG. 8, the above effect can be achieved even if lead forming is performed only on the lead wires.

The surge absorber of the present invention is constructed as described above, and the lead wires soldered to both electrodes of the varistor element have two parallel terminals in the same direction. It is possible to prevent a voltage drop due to inductance from appearing in the line limit voltage, obtain the limit voltage inherent to the varistor, and exhibit good protection characteristics.

Since the four electric terminals are twisted and arranged in the same direction, it is resistant to vibration and can be applied to printed circuit boards etc. very easily.

Furthermore, since the varistor element is essentially sandwiched between four lead wires, and the soldering of the lead wires to the electrodes has a sliding part, the varistor voltage is high, which means the weight of the element. Even large items are less likely to fall off, and automatic solder dipping is possible.

When lead forming is performed so that the pitch between the terminal portions of the lead wires is wider than the thickness of the varistor element, sufficient insulation between the lead wires can be maintained.

[Brief explanation of drawings]

Fig. 1 is a front view of a conventional surge absorber, Fig. 2 is an electrical equivalent circuit diagram showing an example of the application of the conventional product to between lines, and Fig. 3 is a diagram showing the original limiting voltage characteristics of the conventional product and the varistor. , Fig. 4 is a perspective view for explaining the basic configuration of the surge absorber according to the present invention, and Fig. 5 is an electrical equivalent showing an example of application of the surge absorber shown in Fig. 4 to between lines. The circuit diagram, FIGS. 6 and 7 are front views showing an embodiment of the surge absorber according to the present invention, and FIG. 8 is a side view showing another embodiment of the surge absorber according to the present invention. 6... Varistor element, 7, 7'... Electrode, 12゜13.14, 14'... Lead wire.

Claims (2)

[Scope of utility model registration request] (1) Electrodes are provided on both the front and back sides of the varistor element, and the part soldered to the electrode is curved in a U-shape so that two terminals are taken out parallel to each electrode in the same direction. A surge absorber made by soldering the lead wires symmetrically. (2) Bend at least one lead wire outward in the thickness direction of the varistor element, and fold it back again so that it approaches the same line as the varistor element surface, and align the pitch between the terminal parts of the two lead wires in the thickness direction of the varistor element. The surge absorber according to claim 1, which is wider than the thickness of the varistor element described above.