JP3768621B2 - How to use the protective element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the use of protective devices used to protect electrical equipment from overvoltages.
[0002]
[Prior art]
When the device is cut off from the power supply when an overvoltage is applied to the device, a protection consisting of a membrane resistance and a low melting point soluble alloy piece arranged on one side of the insulating substrate and covering one side of the insulating substrate with an insulating layer As shown in FIG. 4, a protective element E ′ and an overvoltage detection energizing circuit F ′, for example, a circuit F ′ formed by connecting a Zener diode D ′ to the base side of the transistor Tr ′ are used. When a reverse voltage greater than the breakdown voltage of the Zener diode D ′ is applied to the device Z ′ between the power source S ′ and the protected device Z ′, a base current flows and the base current is It is known that the collector current flows, the membrane resistance R ′ generates heat, and the low-melting-point soluble alloy piece A ′ is cut off from the power source S ′.
[0003]
However, in the above protective element, even if the device Z ′ is disconnected from the power source by the melting of the low melting point soluble alloy piece A ′, if the device Z ′ is a capacitive load, for example, a storage battery, because of the residual voltage Since the base current continues to flow and the energization heat generation of the membrane resistance R ′ may continue, it is dangerous.
[0004]
Therefore, as shown in FIG. 5 (a), a composite electrode 20 ′ in which a central fuse electrode 21 ′ and a heater one-side T-shaped electrode 22 ′ are combined, and a heater-other-side T-shaped electrode 23 are combined. 'And both side electrodes 24' and 25 'are printed on the substrate 1', and as shown in FIG. 5B, the heater one side T-shaped electrode 22 'and the other side of the heater Membrane resistances R ′ and R ′ are respectively provided between the T-shaped arms of the T-shaped electrode 23 ′, insulating layers i ′ and i ′ are provided on the respective film resistors, and a central fuse of the composite electrode 20 ′ is provided. Low melting point soluble alloy pieces A ′ and A ′ are connected between the electrode 21 ′ and the fuse side electrodes 24 ′ and 25 ′, respectively. Further, as shown in FIG. In addition, it has been proposed to use a protective element covering the outer insulating layer 5 '(Japanese Patent Laid-Open No. 7-153367).
In the protection circuit incorporating this protection element, as shown in FIG. 6, two pairs of membrane resistance R′-low melting point soluble alloy piece A ′ are provided, and each pair of membrane resistances R ′ is heated by energization and heat generation. The melting point soluble alloy piece A ′ is melted.
Thus, when a reverse voltage higher than the breakdown voltage of the Zener diode D ′ is applied to the device Z ′ side, a base current flows through the transistor Tr ′, a collector current flows, and both film resistors R ′ and R ′ The low-melting-point soluble alloy pieces A ′ and A ′ are melted by the energization heat generation of the film resistors R ′ and R ′, and the device Z ′ is disconnected from the power source S ′ and the film resistors R ′ and R 'Is disconnected from the power source S'.
[0005]
[Problems to be solved by the invention]
However, in the above protective element, since there are two pairs of membrane resistance-low melting point soluble alloy pieces, it is necessary to adjust the resistance values of the two membrane resistors, which is difficult to manufacture. -Since it is necessary to provide two sets of low-melting-point soluble alloy pieces in a plane, it is disadvantageous for reducing the size of the protective element.
In addition, an insulating layer on the film resistance, for example, a glass film, is formed by screen printing, and it is difficult to avoid unevenness due to the screen mesh. It is difficult to guarantee smooth spheroidization of the alloy pieces.
[0006]
The object of the present invention is a protection element that detects an overvoltage of a device, energizes and heats the membrane resistance to melt the low melting point soluble alloy piece, and cuts off the device and the membrane resistance from the power source. An object of the present invention is to provide a method of using a protective element that is easy to operate and excellent in operation.
[0007]
[Means to solve the problem]
The method of using the protective element according to the present invention includes providing a first electrode, a second electrode, a third electrode, and a fourth electrode on one surface of an insulating substrate, providing a resistor across the second electrode and the fourth electrode, Low melting point soluble alloy pieces A and B are connected between the electrode and the second electrode and between the second electrode and the third electrode, respectively, and a flux is applied to the low melting point soluble alloy piece. The melting point of the low-melting-point soluble alloy piece A and the melting point of the low-melting-point soluble alloy piece B of the protective element formed by covering one side and covering the insulating layer are different from each other, and each low-melting-point soluble alloy piece is applied to different circuit parts. Used as a fuse, connected to an overvoltage detection energization circuit that detects different overvoltages and energizes and heats the resistance of the protective element at different temperatures, and energizes and heats the resistance with a small overvoltage, and one of the low melting point soluble alloy pieces One circuit part is disconnected from the power supply by fusing, and then a large overvoltage is applied. Anti the by electric heating, characterized in that interrupting the other circuit portion from the power supply in the fusing of the other low-melting fusible alloy piece.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a protective element used in the present invention .
In FIG. 1, 1 is a heat-resistant insulating substrate, for example, a ceramic plate. Reference numerals 21 to 24 denote film-like first to fourth electrodes printed on one surface of the insulating substrate, and the second electrode 22 is provided between the tip of the first electrode 21 and the tip of the third electrode 23. Further, the fourth electrode 24 is provided at a predetermined interval from the second electrode 22.
Reference numerals 31, 33, and 34 denote lead wires (insulation-coated wires) connected to the first electrode, the third electrode, and the fourth electrode, respectively.
R is a film resistance provided by printing over the second electrode 22 and the fourth electrode 24.
A is a low melting point soluble alloy piece connected between the tip of the first electrode 21 and the second electrode 22, and B is a low melting point possible connected between the tip of the second electrode 22 and the third electrode 23. If it is a molten alloy piece and the low melting point soluble alloy pieces A and B are of the same material and shape, they may be continuous lines as shown in the figure.
4 is a flux applied on the low melting point soluble alloy pieces A and B.
Reference numeral 5 denotes an insulating layer provided so as to cover one surface of the insulating substrate 1, and an insulating material which can be coated at room temperature so as not to melt and flow the low melting point soluble alloy piece or flux, for example, room temperature curing epoxy resin Is used.
[0010]
When the overvoltage acts on the protected device, the protection element is used to cut off the device from the power source, FIG. 2 is a circuit diagram for explaining the use state, and E is the protection device according to the present invention. F represents an overvoltage detection energization circuit.
In FIG. 2, the protection element E and the overvoltage detection energization circuit F according to the present invention are incorporated between the protected device Z and the power source S, the collector of the transistor Tr is connected to the fourth electrode 24 of the protection element E, and the Zenadio -Connect the high-voltage side electrode of D and the third electrode 23 of the protection element E to the high-voltage side terminal of the protected device Z, and connect the first electrode 21 of the protection element E to the high-voltage side terminal of the power source S. The emitter of the transistor Tr is grounded.
In the circuit shown in FIG. 2, when an overvoltage higher than the breakdown voltage of the Zener diode D acts on the device Z, a base current flows through the transistor Tr, and accordingly, a large collector current flows and the film resistance R is heated. The generated heat is transmitted to the low melting point soluble alloy pieces A and B through the second electrode 22 so that both the low melting point soluble alloy pieces A and B are melted while receiving the active action of the already melted flux. Z is disconnected from the power source S and the membrane resistance R is disconnected from the power source S. Therefore, after the low melting point soluble alloy piece B is melted, even if the overvoltage state of the device Z is maintained due to residual charge and the transistor Tr is in a conductive state, the film due to the melting of the low melting point soluble alloy piece A Since the resistance R is cut off from the power source S, it is possible to eliminate the continued heating of the film resistance R.
In the above description, the high voltage side electrode of the Zener diode D may be connected to the first electrode 21 side.
[0011]
In the above, for the melting of the molten low melting point metal, the insulating substrate repels the molten metal and the electrode wets well with the molten metal, and the surface smoothness of the insulating substrate is also an important condition (melting) Elements that make it easier for metal to flow). Thus, the ceramic plate is advantageous in that it has superior surface smoothness compared to a glass screen printed film.
FIG. 3 is a circuit diagram showing a method of using the protective element according to the present invention. The low melting point soluble alloy piece B is used as a fuse for the circuit part Zb, and the low melting point soluble alloy piece A is used for the circuit part Za. In FIG. 3, the breakdown voltage Vb of the Zener diode Db is made lower than the breakdown voltage Va of the Zener diode Da, and the melting point of the low melting point soluble alloy piece B is changed to that of the low melting point soluble alloy piece A in FIG. The melting point is made lower, the Zener diode Db is made to conduct at an overvoltage of Vb to Va, a base current is passed, and the resistance R of the protective element E is energized and heated by a collector current corresponding to the base current. The fusible alloy piece B is melted to cut off the circuit portion Zb from the power source (ss' is a power supply terminal). After that, when an overvoltage of Va or higher acts, the diode Da is turned on to generate a base current. Compatible with this base current Is energized heating resistor R of the protective element E in the collector current is blow the low-melting fusible alloy piece A by power supply circuit section Za (s-s' power supply terminal) can be cut off from.
[0012]
In the protective element, a ceramic plate having a thickness of 100 to 1200 μm, for example, a 96% alumina ceramic plate can be used for the insulating substrate. In addition, it is possible to use a metal base material that has been insulated. The planar dimensions of the insulating substrate are usually (3 mm to 20 mm) × (3 mm to 20 mm) square or rectangular.
In the protective element, the low melting point soluble alloy piece includes a low melting point alloy round wire having a liquidus temperature of 75 ° C. to 300 ° C. and a diameter of 100 μm to 1200 μm, and a low melting point alloy square wire or a low melting point alloy having the same cross-sectional area. Foil can be used.
In the protective element, the electrode is a conductor paste (a mixture of conductor powder and glaze, and the conductor powder is screen-printed with silver-platinum, silver-palladium, or copper) and baked. Can be formed. Moreover, an insulating substrate with electrodes can also be obtained by etching the copper foil of the copper foil laminated substrate.
In the protective element, the film resistance can be formed by screen-printing a resistance paste such as ruthenium oxide powder or a mixture of carbon powder and glaze on an insulating substrate and baking it. Usually 1 to 30 μm. A Ti—Si based film resistance can also be used as the film resistance. When it is necessary to adjust the resistance value of the film resistance, trimming is performed. At this time, a glass protective film is formed on the film resistance so that the film resistance is not cracked. it can. Furthermore, when protection is required for long-term stability, a protective film such as a glass film is formed on the film resistance. Any of the overlapping states of the film resistance end portion and the electrode end portion may be the lower side. Instead of these film resistors, chip resistors can be used.
[0013]
In the protective element, the flux is used to prevent oxidation of the low-melting-point soluble alloy piece and to dissolve some oxide film of the low-melting-point soluble alloy piece to facilitate the division of the molten alloy. A material containing rosin as a main component and an activator (for example, diethylamine hydrochloride) added as necessary can be used.
[0014]
In order to manufacture the protective element, the first electrode to the fourth electrode are formed on one surface of the insulating substrate, the film resistance is printed, the glass protective film is formed on the film resistance, and the resistance value is adjusted by trimming as necessary. If adjustment and resistance protection are required, a glass film is formed on the film resistance, the low melting point soluble alloy pieces A and B are connected, the lead wire is connected to the electrode, and the low melting point soluble alloy piece A method can be used in which a flux is applied to the substrate, the substrate is then immersed in an epoxy resin solution at room temperature, and the immersion coating layer is dried and cured.
[0015]
【The invention's effect】
According to the method of using the protection element according to the present invention , different circuit portions can be cut off from the power supply against different overvoltages . In addition, the protective element has one resistor and two low melting point soluble alloy pieces, and when an overvoltage is applied to the protected device, both the low melting point soluble alloy pieces are blown off by energization heat generation of the resistor. The protected device can be cut off from the power source and the resistor can be cut off from the power source, and a resistor is provided for each of the low melting point soluble alloy pieces in the conventional example. Compared to a configuration in which one low melting point soluble alloy piece is melted and the other resistor melts the other low melting point soluble alloy piece, the structure is simpler.
[0016]
Also, unlike the conventional example in which an insulating glass film is provided on the film resistance, and the low melting point soluble alloy piece is arranged on the insulating glass film, the film resistance and the low melting point soluble alloy piece are not overlapped. A low melting point soluble alloy piece is placed on a ceramic insulating substrate having a smoother surface than the surface of the insulating glass film (on the screen printing, unevenness due to the screen mesh is unavoidable). Therefore, the molten alloy can flow smoothly and can be quickly divided, and excellent operability can be guaranteed.
Further, when in need of adjusting the resistance value, since the resistance value adjustment by trimming may be performed for one of the film resistors can reduce the number of manufacturing steps, Ru manufacturing advantage der.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of a protection element used in the present invention.
FIG. 2 is an explanatory diagram showing a reference example of how to use the protection element shown in FIG.
FIG. 3 is an explanatory diagram showing an example of a circuit used in a method of using a protection element according to the present invention .
FIG. 4 is an explanatory diagram showing a conventional protection circuit.
FIG. 5 is an explanatory view showing a conventional protection element.
6 is an explanatory diagram showing a protection circuit using the protection element of FIG. 5; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Insulation board | substrate 21 1st electrode 22 2nd electrode 23 3rd electrode 24 4th electrode A Low melting point soluble alloy piece B Low melting point soluble alloy piece R Resistance 4 Flux 5 Insulating layer E Protection element F Overvoltage detection energization circuit Z Covered Protective equipment S Power supply

Claims (1)

A first electrode, a second electrode, a third electrode, and a fourth electrode are provided on one surface of the insulating substrate, a resistor is provided between the second electrode and the fourth electrode, and the second electrode is provided between the first electrode and the second electrode. The low melting point soluble alloy pieces A and B are respectively connected between the electrode and the third electrode, the flux is applied to the low melting point soluble alloy piece, and one side of the insulating substrate is covered to cover the insulating layer. The melting point of the low melting point soluble alloy piece A of the protective element is different from the melting point of the low melting point soluble alloy piece B, and each low melting point soluble alloy piece is used as a fuse for different circuit parts to detect different overvoltages. Connect an overvoltage detection energization circuit that energizes and heats the resistance of the protection element at different temperatures, energizes and heats the resistor with a small overvoltage, and cuts one circuit part from the power supply by fusing one low melting point soluble alloy piece. After that, a large overvoltage causes the resistor to generate heat and allow the other low melting point. Using the protection device characterized by blocking the other circuit portion from the power supply in fusing of the alloy strip.

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