JPH0775190B2 - Surge absorption element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surge absorbing element for protecting electronic components from a surge such as a transient abnormal voltage or a lightning surge that enters an electronic device. More specifically, it relates to a surge absorbing element in which a pair of electrodes facing each other is hermetically sealed in an insulating tube.

[0002]

2. Description of the Related Art A surge absorbing element of this type is connected to a pair of input lines of an electronic component in parallel with the electronic component, and is configured to operate at a voltage higher than the operating voltage of the electronic component. That is, the surge absorbing element is a resistor having a high resistance value at a voltage lower than the discharge starting voltage, but becomes a resistor having a low resistance value of several tens Ω or less when the applied voltage is equal to or higher than the discharge starting voltage. When a surge voltage such as a lightning surge is momentarily applied to an electronic component, the surge absorbing element discharges and absorbs the surge voltage. As a result, the surge voltage is not applied to the electronic component, and the failure or malfunction of the electronic device due to the surge voltage is avoided.

Among the conventional gap type surge absorbers,
As shown in FIG. 6, the microgap type discharge tube has a cylindrical ceramic body 1 whose outer peripheral surface is coated with a conductive film 1a. Cap electrodes 2 and 3 are attached to both ends of the ceramic body 1. There are several tens on the outer peripheral surface of the central portion of the ceramic body 1 to which the cap electrodes 2 and 3 are attached.
A microgap 1b of μm is formed. Sealing electrodes 6 and 7 having lead wires 4 and 5 welded to the outer surfaces thereof are in contact with the end surfaces of the cap electrodes 2 and 3, respectively. Surge absorption element 9
Holds the ceramic body 1 with the cap electrodes 2 and 3 and the sealing electrodes 6 and 7 with the lead wires 4 and 5 in the glass tube 8 in a state of being in contact with each other as shown in the figure. It is made by filling the tube 8 with an inert gas and sealing the glass tube 8 to the electrodes 6 and 7.

[0004]

In the conventional surge absorbing element described above, a microgap is formed on the outer peripheral surface of the ceramic body by trimming the conductive film with a laser beam. Since the setting of the processing conditions of this laser processing apparatus is complicated, there is a problem that it takes time to form the microgap by the laser beam. In addition, since the size of the microgap formed by the laser beam tends to vary, this processing requires skilled technology,
There is a drawback that the surge absorbing element cannot be manufactured easily. In addition, since discharge during surge absorption occurs on the outer surface of the circumference of the ceramic body, it is necessary to secure a certain amount of space around this ceramic body.For this reason, cap electrodes are attached to both ends of the ceramic body. I had to wear it. As a result, the inner diameter of the glass tube becomes large and the overall size of the surge absorbing element becomes considerably large. Further, there is a problem that the thickness of the ceramic body has to be increased for the above laser processing.

An object of the present invention is to provide a surge absorbing element which can be simply and efficiently manufactured by forming a gap without resorting to complicated and skillful laser processing. Another object of the present invention is to provide a surge absorbing element that can be manufactured in a short size.

[0006]

In order to achieve the above object, the structure of the present invention will be described with reference to FIGS. 1 and 2.
The surge absorbing element 19 of the present invention includes a ceramic cylindrical body 12 covered with a conductive film 12a, an insulating ceramic spherical body 11 arranged on one side of the cylindrical body 12 and having a diameter larger than the inner diameter of the cylindrical body 12, A pair of electrodes 16 and 17 for sandwiching the ceramic cylinder 12 and the ceramic sphere 11 which are arranged to have an outer diameter substantially the same as the outer diameter of the ceramic cylinder 12, and a ceramic cylinder sandwiched by the electrodes. 12 and the ceramic sphere 11 and is filled with an inert gas, and is provided with an insulating tube 18 sealed to the outer periphery of the electrode.

The insulating ceramic sphere 11 has a volume resistivity of 10 ¹⁴ such as alumina, mullite, zirconia, steatite, forsterite or beryllia.
Ceramics having a high insulating property of Ωcm or more are preferable. The diameter of the insulating ceramic sphere 11 is equal to that of the ceramic cylinder 12.
Must be larger than the inner diameter of. Ceramic cylinder 1
2 is not particularly limited as long as it is an insulating material, but may be the same material as the insulating ceramic sphere 11. Conductive coating 1 formed on the surface of a ceramic cylindrical body 12 encapsulating it
2a is preferably a metal thin film having excellent conductivity such as titanium, nickel, tin oxide or titanium nitride. This film is formed by wrapping the entire cylindrical body 12 by sputtering, vacuum deposition or the like. The electrodes 16 and 17 are insulating tubes 18
A material having a thermal expansion coefficient close to that of the insulating tubular body 18 is selected so that the tubular body is not cracked during sealing. When the insulating tube is a glass tube made of borosilicate glass, lead glass or the like, a Dumet wire or an amber (Invar) with which the thermal expansion coefficient of the glass tube is matched is preferable. It is possible to weld the lead wires 14 and 15 to the outer surfaces of the electrodes 16 and 17 before the insulating tube 18 is sealed. A rare gas such as argon gas, nitrogen gas, or a mixed gas thereof is sealed in the insulating tube body 18.

The surge absorbing element of the present invention is manufactured by the following method. First, if necessary, one electrode 16 having the lead wire 14 welded thereto is inserted into one end of the insulating tube body 18 so that the other end of the insulating tube body 18 is positioned above. Stand the body 18 vertically. Then, the conductive film 1
The ceramic cylindrical body 12 with 2a and the insulating ceramic sphere 11 are dropped into the insulating tube body 18 in this order. Next, if necessary, the other electrode 17 having the lead wire 15 welded thereon is inserted into the insulating tubular body 18. With the insulating ceramic sphere 11 and the ceramic cylinder 12 held between the electrodes 16 and 17, the inside of the insulating tube 18 is evacuated to remove air, and an inert gas is introduced instead. When the insulating tubular body 18 and the electrodes 16 and 17 are heated by a carbon heater (not shown) in this state, the insulating tubular body 18 is sealed to the electrodes 16 and 17.

The surge absorbing element of the present invention may have a structure in which an insulating ceramic sphere 11 is sandwiched between a pair of ceramic cylinders 12 and 13 as shown in FIG. 3, and as shown in FIG. First and second insulating ceramic spheres 11a and 11b are arranged on both sides of the cylindrical body 12,
The first insulating ceramic sphere 11a is provided between the electrode 16 and the ceramic cylinder 12, and the electrode 17 and the ceramic cylinder 12 are provided.
The structure may be such that the second insulating ceramic spheres 11b are sandwiched between them. Since the surge absorbers of FIGS. 3 and 4 are bilaterally symmetrical, they have no polarity and are preferable. Further, as shown in the figure, the lead wires 14 and 15 can be welded to the electrodes 16 and 17 of the surge absorbing element of the present invention.

[0010]

When the surge voltage is applied to the electrodes 16 and 17,
Arc discharge occurs between the conductive film 12a and the electrode 17 through the gap formed by the insulating ceramic sphere 11. Since the insulating ceramic sphere 11 is seated on the hollow end of the ceramic cylindrical body 12, the holding position of the ceramic sphere 11 is constant and a stable discharge space is secured. Since the clearance between the outer surface of the ceramic sphere 11 and the inner wall of the insulating tube 18 is large, it is possible to withstand a relatively large surge.

[0011]

EXAMPLES Next, examples of the present invention will be described together with comparative examples. The invention is not limited to this example. <Example> As shown in FIGS. 1 and 2, the diameter is 0.5 mm.
The insulating ceramic sphere 11 made of zirconia is seated on the hollow end of the ceramic cylindrical body 12 covered with the conductive coating 12a made of titanium. As a result, the spherical surface of the ceramic sphere 11 contacts the end of the ceramic cylinder 12. The film 12a is formed by sputtering.
The ceramic cylindrical body 12 has a length of 1 mm, an outer diameter of 1 mm, an inner diameter of 0.4 mm, and is made of alumina. The electrode 16 having the lead wire 14 welded to the outer surface of the ceramic cylindrical body 12
Electrode 1 having a lead wire 15 welded to the outer surface of the
7 abuts on the spherical surface of the insulating ceramic sphere 11. The pair of electrodes 16 and 17 is a 1 mm diameter Dumet wire cut into a length of about 1.3 mm. Ceramic cylinder 12 in glass tube 18 made of lead glass
And the insulating ceramic sphere 11 are sandwiched between the electrodes 16 and 17, and in this state filled with argon gas, the insulating tube 18
Are sealed on the outer periphery of the electrodes 16 and 17. The glass tube 18 has an outer diameter of 2 mm, an inner diameter of 1.1 mm, and a length of 4 mm.

<Comparative Example> The aforementioned surge absorbing element 9 shown in FIG. 6 was used as a comparative example. Here, the ceramic body 1 has a length of 3 mm and a diameter of 1 mm, and is made of mullite.
A conductive film 1a made of the same material and having the same thickness as that of the embodiment is formed on this surface, and the outer peripheral surface of the central portion has a width of about 50 μm.
A microgap 1b of m is formed. The end surfaces of the stainless steel cap electrodes 2 and 3 each have a length of about 2 mm and a diameter of about 1.5 mm.
7 is abutted. The ceramic body 1 with the cap electrodes 2 and 3 and the sealing electrodes 6 and 7 with the lead wires 4 and 5 are housed in a glass tube 8, and the glass tube 8 is filled with argon gas to form the electrodes 6 and 7. Is sealed to. The glass tube 8 has an outer diameter of 2.7 mm, an inner diameter of 1.7 mm, and a length of 7.5 m.
m.

An electrostatic life test and a pseudo surge response test were conducted on the surge absorbing elements of the examples and comparative examples. <Electrostatic life test> Output terminal 21 of the circuit shown in FIG.
An electrostatic life test was conducted by connecting the lead wires of the surge absorbing element to Nos. 22 and 22. In FIG. 5, 23 is a 10 kV DC power source, 24 is a capacitor with an electrostatic capacity of 1000 pF, and 25
Is a 250Ω resistor, and 26 is a charge / discharge changeover switch. The switch 26 is switched to the contact a as shown by the solid line in the figure, and a voltage of 10 kV is applied to the capacitor 24 to charge the capacitor 24. Then, the switch 26 is switched to the contact b as shown by the broken line in the figure to discharge the capacitor 24. Then, static electricity was applied to the surge absorbing element. The above-mentioned static electricity was repeatedly applied 1000 times to the surge absorbing elements of Examples and Comparative Examples, and the discharge starting voltage, insulation resistance, and capacitance of each surge absorbing element before and after the test were measured. As a result, the surge absorption element of the comparative example before the test had an average discharge starting voltage of 40%.
0 V, standard deviation 5 V (100 samples), while the surge absorbing element of the example has an average discharge starting voltage of 411 V, standard deviation 29 V (100 samples), and an insulation resistance value of 10 ¹¹ Ω or more. The capacitance was 0.5 pF. When measured after the test, the surge absorption elements of the example and the comparative example have an average firing voltage of 411 V and an average of 400 V, respectively.
And the insulation resistance value is 10 ¹¹ Ω or more and the electrostatic capacitance is 0.
It was 5 pF, and there was no change in each value.

<Pseudo Surge Response Test> A voltage surge of (1.2 × 50) μsec−2 kV was repeatedly applied 100 times to the surge absorbing elements of Examples and Comparative Examples, and the operating voltage was measured. The surge absorbing elements of the examples and the comparative examples were designed to have a DC discharge inception voltage of 400V. The surge absorbing element of the comparative example started discharging at an average of 610V and its standard deviation was 50V, whereas the surge absorbing element of the example started discharging at an average of 650V and its standard deviation was 71V. It was From the above, it was found that the surge absorbing element of the example is not inferior in durability and surge absorbing characteristics to the surge absorbing element of the comparative example.

[0015]

As described above, since the surge absorbing element of the present invention forms the microgap without the conventional laser processing, it can be simply and efficiently manufactured.
Moreover, it has the same electrical characteristics as the conventional surge absorbing element. Also, since there is no handling step during laser processing, the length and thickness of the ceramic cylinder can be reduced, and the volume of the main body can be reduced to 1/3 or less of the conventional product. Can be smaller.

[Brief description of drawings]

FIG. 1 is a sectional view of a surge absorber according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view thereof.

FIG. 3 is a sectional view of a surge absorber according to another embodiment of the present invention.

FIG. 4 is a sectional view of a surge absorbing element according to still another embodiment of the present invention.

FIG. 5 is an electrostatic life test circuit of Examples and Comparative Examples.

FIG. 6 is a sectional view of a conventional surge absorber.

[Explanation of symbols]

 11 Insulating Ceramic Sphere 12, 13 Ceramic Cylindrical Body 12a, 13a Conductive Film 14, 15 Lead Wire 16, 17 Electrode 18 Insulating Tube 19 Surge Absorbing Element

Claims (7)

[Claims] 1. A ceramic cylindrical body (12) covered with a conductive film (12a), and the cylindrical body (1) arranged on one side or both sides of the cylindrical body (12).
Insulating ceramic sphere with a diameter larger than the inner diameter of 2)
(11), a pair of electrodes having an outer diameter substantially the same as the outer diameter of the ceramic cylinder (12) and sandwiching the arranged ceramic cylinder (12) and the ceramic sphere (11) (16, 17), the electrode (16, 17) wrapped around the ceramic cylinder (12) and the insulating ceramic sphere (11) sandwiched between the electrodes (16, 17) and filled with an inert gas Insulating tube sealed on the outer circumference
(18) A surge absorber with and. 2. Between a pair of ceramic cylinders (12, 13) of the same shape and size which are covered with a conductive film (12a, 13a), and between the pair of ceramic cylinders (12, 13). An insulating ceramic sphere (11) having a diameter larger than each inner diameter of the ceramic cylinders (12, 13) arranged, and an outer diameter substantially the same as each outer diameter of the ceramic cylinders (12, 13). The pair of ceramic cylinders (1
2, 13) and a pair of electrodes (16, 17) sandwiching the ceramic sphere (11), and a pair of ceramic cylinders sandwiched by the electrodes (16, 17)
(12, 13) and a surge absorbing element comprising an insulating ceramic sphere (11) and an insulating tube (18) which is filled with an inert gas and sealed to the outer periphery of the electrodes (16, 17) . 3. The insulating ceramic sphere (11) is made of alumina,
The surge absorbing element according to claim 1 or 2, which is mullite, zirconia, steatite, forsterite or beryllia. 4. The surge absorbing element according to claim 1, wherein the conductive film (12a, 13a) is titanium, nickel, tin oxide or titanium nitride. 5. The surge absorbing element according to claim 1, wherein the insulating tube body (18) is a glass tube. 6. The surge absorbing element according to claim 1, wherein the electrodes (16, 17) are Dumet wires or amber. 7. The surge absorbing element according to claim 1, wherein the inert gas is a rare gas, a nitrogen gas, or a mixed gas thereof.