JPS5927085B2 - barista - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a varistor that absorbs surge voltage and noise voltage, which operates effectively against surge noise having high frequency components and provides a lower limit voltage.

FIG. 1 shows the structure of a conventional varistor.

In the figure, 1 is a disk-shaped varistor element, 2 and 2'(2' is not shown) are electrodes baked (or metallized) on both the front and back surfaces of the element 1, and 3 and 3.
' is electrode 2. Soldering to z is a lead wire that is electrically connected.

FIG. 2 shows a circuit when the conventional varistor shown in FIG. 1 is connected to, for example, a power supply line 4.

5 is a varistor element, 6 and `` are the above lead wires 3, 3'
is the stray inductance of

Now, when a surge noise voltage is applied between power line 4,
Current flows in the direction of the arrow.

At this time, the voltage drop V- due to stray inductance 6 and σ
= Ldi/dt.

Here, L is the lead floating inductance, and d14t is the rate of change of current.

Therefore, if the lead wires 3 and 31 are long, or if the current contains high frequency components, the voltage drop will increase, and this voltage will be superimposed on the limited voltage of the varistor element 5, and eventually the Paris As a result, the limiting voltage increases and the protective effect decreases.

The voltage-current characteristics shown in FIG. 3 show this situation.

In FIG. 3, curve A is the limiting voltage characteristic of only the varistor element 5,
Curve B is the limiting voltage characteristic in which the voltage drop occurring in the stray inductance 6, C is superimposed on the limiting voltage characteristic of the varistor element 5, and the varistor shown in Fig. 1 is used in the power supply line 4, etc. as shown in Fig. 2. The limiting voltage characteristic at this time is curve B.

As described above, in conventional varistors, the limiting voltage increases significantly against surge noise voltages including high frequencies, and the protection characteristics thereof are not sufficient.

The present invention has been made in order to eliminate the above-mentioned problems in the conventional art, and is intended to provide a varistor with excellent characteristics.

Hereinafter, one embodiment of the present invention will be described with reference to FIG. 4A-9.

In FIG. 4A, 7 is a disk-shaped varistor element mainly made of metal oxide such as ZnO, and electrodes 8, 8/ are provided on both the front and back surfaces of the element.

9 and G are lead wires each consisting of one lead wire, and the portions connected to the electrodes 8 and 8' are planar coil parts 9c and 9c' symmetrical with respect to the varistor element 7, and the coil parts 9c , 9c' are connected to the electrodes 8, 8' by soldering, etc., and both ends of each are electrical terminals 9a s.
9b, 9a'.

It is 9b'.

FIG. 5 shows a schematic enlarged configuration of a Taharista having such a lead wire 9,9' structure, and the operating principle of the varistor will be explained with reference to FIG.

Now, the electrical terminals 9 a s 9 a' of the lead wires 9, 9'
When a high frequency pulse is applied between the terminals 9a and 9a'
Although the current density passing through the nearby varistor element 7 becomes high, the so-called coil portions 9c, 9c near the terminals 9b, 9b'
In the central part passing through ', the current density is changed to terminal 9a due to the inductance of coil parts 9c and 9c'.

9 is lower than around a', and the steepness of the rise of the current is also reduced because it passes through the inductance.

Therefore, the limited voltage between the terminals 9b and 9b' is greatly reduced, and the adverse effects caused by the inductance of the conventional lead wires can be prevented.

FIG. 6 and FIG. 1 respectively show modified examples of the shape of the coil portion of the lead wire according to the present invention.
In FIG. 7, the planar coil portion 11 has a meandering shape.

Now, when providing coil parts 9c, 9c' to the lead wires 9, 9' connected to both electrodes 8, 8' of the varistor element 7 as in the embodiment shown in FIG. For orderliness, both coil parts 9c, 9c' must curve symmetrically with respect to the varistor element 7.

In addition, if the thickness of the electrodes 8, 8' is too thick,
Since the current distribution through the electrode 8' becomes better and the above-mentioned current density distribution begins to become uniform, for example, the thickness of the silver electrode baking structure must be 10 μm or less.

Here, the portion of one lead wire connected to the electrode may be a planar coil portion, and the other lead wire may be connected to the electrode in a U-shape having two terminals.

In this case, although the effect is reduced compared to the embodiment shown in FIG.
It was confirmed that the effect was superior to that of the conventional example.

In addition, the varistor of the present invention is used by covering the varistor element and the coil portion of the lead wire with an insulating resin such as an epoxy resin.

The varistor of the present invention is constructed as described above, and has the following effects.

b) By making the part connected to the electrode of the lead wire a planar coil part, it is possible to reduce the current density and current increase rate on the load side, thereby reducing the limiting voltage and improving the protection effect. Become.

Mouth) By making the coil portion of the lead wire connected to both electrodes symmetrical with respect to the varistor element, the current flow becomes orderly and the effect of reducing the limiting voltage becomes greater.

c) By setting the thickness of the electrode to 10 μm or less, the current density within the varistor element is prevented from becoming uniform, and the limiting voltage is more effectively reduced.

[Brief explanation of drawings]

Fig. 1 is a front view of a conventional varistor, Fig. 2 is an equivalent circuit diagram showing an application example of the varistor, Fig. 3 is a voltage-current characteristic diagram of the varistor, and Fig. 4 A. The mouth is a front view and a side view showing an embodiment of the varistor according to the present invention, FIG. 5 is a horizontal enlarged cross-sectional view of the varistor, and FIGS. 6 and 7 are the shape of the coil portion of the lead wire constituting the varistor. It is a block diagram which shows the modified example of each. 7... Varistor element, 8, 8'... Electrode, 9, 9'... Lead wire, 9a/9b s
9 a'・9 b'・・・Electrical terminal, 9c, 9
c', 10.11... Coil part.

Claims (1)

[Scope of Claims] Electrodes are provided on both the front and back surfaces of a varistor element mainly made of metal oxide such as I ZnO, and two lead wires are connected from each end of each lead wire electrically connected to each electrode. A varistor, wherein an electrical terminal is taken out, and a planar coil portion is formed in a portion of at least one of the lead wires connected to the electrode. 2. The varistor according to claim 1, wherein each coil portion of the two lead wires connected to both electrodes of the varistor element is symmetrical with respect to the varistor element. 3. The varistor according to claim 1 or 2, wherein the thickness of the electrode applied to the varistor element is 10 μm or less.