JPS605735A - Circuit protecting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit protection device for protecting a circuit from transient abnormal voltages, and particularly to a circuit protection device using a fully bent oxide varistor as a circuit protection element.

In recent years, with advances in electronic technology, semiconductor elements have come to be used in many electronic devices, but semiconductor elements are vulnerable to transient abnormal voltages (surges), so surges can occur in the circuits of electronic devices. It is necessary to provide a means to absorb the For example, as pollution regulations and safety regulations become stricter, automobiles are equipped with complex electronic circuits using a large number of semiconductor elements. By the way, the so-called load dump surge, which occurs when a battery terminal is disconnected for some reason, is the other side of the surge that occurs in automobiles.The surge energy is as large as 1oO to 300J at maximum, so conventional glue absorbers cannot handle it. It becomes large.

Therefore, the inventors first formed electrodes on a honeycomb-structured ceramic resistor made of gold R oxide J-1, which has varistor properties, and has multiple through holes. proposed an optimal circuit protection element for use in low-voltage circuits of automobiles (Japanese Patent Application No. 11487-1987).
No. 5).

By the way, in the above-mentioned circuit protection element, a region with low dielectric strength may partially occur during the ceramic firing process, and if a short circuit occurs in this region during use, the vehicle battery will be discharged. .

In view of the above-mentioned problems, the present invention provides a circuit protection device using the previously proposed circuit protection device, in which even if a short circuit occurs within the device, the effects of the short circuit will not spread to the battery, etc. The purpose is to

That is, the circuit protection device of the present invention has a plurality of through holes in a metal oxide ceramic body having varistor characteristics to form a honeycomb structure, and the through holes are alternately connected to positive and negative power supply lines using lead members. a circuit protection element that is provided with an electrode connected to a power supply line and forms a plurality of varistor elements made of partition walls that partition the through holes of the honeycomb structure between both power supply lines; and the positive and negative power supply lines. 21 leading to the electric wire]
A current limiting element is provided in the middle of each lead wire of at least one of the lead wire groups.

Hereinafter, the present invention will be explained with reference to illustrated embodiments.

FIG. 1 shows an overall sectional view of the circuit protection device, in which a circuit protection element 2 is disposed inside the device case 1. Element 2
is a ceramic honeycomb structure mainly composed of zinc oxide and having a large number of through holes 21, and is elastically supported within the case 1 by coil springs 3 at predetermined locations on the outer periphery. An electrode is formed on the inner surface of the through hole 21 by baking silver paste or the like. Lead jacks 4a and 71b are inserted alternately into the through hole 21 from both openings, and each jack 4a and 4b is elastically connected to the electrode by a leaf spring portion 41 (see FIG. 2) formed at its tip. are doing.

Each base end of the jack 4a inserted from the left side of the figure is fixed to the positive terminal 5 by brazing or the like. on the other hand,
One end of a fuse 6 is connected to each jack 4b inserted from the right side in the figure by soldering, and the other end of the fuse 6 is fixed to the negative terminal 7. ”
As the Niki Hikoze 6, a commercially available fuse of 5 to IOA can be used.

The terminal 5 is fixed to the case 1 with bolts 5a, and one end of a cable 9 inserted through the gasket 8 is connected to the terminal 5. The other end of the cable 9 is connected to a positive electrode of a battery (not shown).

On the other hand, the terminal 7 is fixed to the case 1 by a bolt 7a, and is electrically connected to the bracket 10. The bracket 10 is used to fix the case 1 to the engine room of a vehicle, etc., and the terminal 7 is grounded to the main body through this bracket.

” - The operation of a circuit protection device having the configuration as shown in
Explain.

The circuit protection element 2 normally exhibits a high resistance 1iff and hardly allows current to flow therethrough, but when a surge voltage occurs in the battery line, the resistance value rapidly decreases and a surge current flows. ? I
'That is, the four-noge current flowing from the cable 9 reaches the lead jack 4a via the terminal 5, and the surge current that reaches the jack 4a flows through the ceramic partition wall exhibiting varistor characteristics and is phase-cornered. It reaches the jack 4h on the ground side, and flows from the fuse 6 connected in series thereto, through the terminal 7 and the bracket 10, to the ground.

In the circuit protection element 2, varistor elements each made of a partition wall are formed between the jacks 4a and 4b in contact with the partition wall. If there is a portion of the plurality of varistor elements with low dielectric strength, a short circuit occurs in this portion and a large current flows. Thus, in the present invention, the fuse 6 connected in series to each jack 41) instantaneously blows out to cut off the short circuit current.

In this way, the defective varistor element with low dielectric strength voltage is separated from the circuit, and the remaining normal varistor element absorbs subsequent surges appropriately.

As described above, the circuit protection device of the present invention connects a fuse in series to the lead jacks provided on the ceramic resistor constituting the circuit protection element, thereby preventing short-circuiting of the varistor element formed between the lead jacks. This is to cut off the large current and prevent Fj%5 from spreading to other circuit components such as the battery.

FIG. 3 shows a further embodiment of the present invention, in which a positive temperature coefficient thermistor (PC) 11 as a current limiting element is installed on the inner surface of the through hole 21 of the circuit protection element 20 at the elastic contact part of the lead jack 4. It is formed. When a varistor element made of a partition wall is short-circuited and a large current flows through the thermistor 11, the resistance of the thermistor 11 increases due to self-heating, and the short-circuit current is quickly reduced. Such a structure also provides the same effect as the above embodiment.

As described above, the circuit protection device of the present invention has a circuit protection element formed of a plurality of varistor elements, and by connecting a current limiting element in series with each varistor element, the short circuit of the varistor element can prevent other circuit components from being damaged. This effectively prevented the spread of the impact.

[Brief explanation of the drawing]

Fig. 1 is an overall cross-sectional view of a device showing one embodiment of the present invention, Fig. 2 is a front view of the tip of a lead jack, and Fig. 3 is a partial cross-section of a circuit protection element showing another embodiment of the present invention. It is a diagram. 2...Circuit protection element 21...Through holes 4.4a, 4b...Lead jack 5...
...Positive 1 side terminal 6.11...Current limiting element 7...Negative terminal Fig. 1 Fig. 2 Otsu A

Claims (1)

[Claims] A plurality of through holes are provided in a metal oxide ceramic body having varistor characteristics to form a honeycomb structure, and electrodes are alternately connected to a positive power supply line and a negative power supply line by lead members in the through holes. a circuit protection element forming a plurality of varistor elements made of partition walls that partition the through holes of the honeycomb structure between both feed lines; and -F2 two sets of lead wires leading to a positive feed line and a negative feed line. at least one of the group,
A circuit protection device consisting of a current limiting element inserted in the middle of each lead wire.