JP2000068107A - Trip-time controlling structure of circuit protective device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control easily a trip time without increasing of the number of assembling processes and components of a structure. SOLUTION: A circuit protective device 4a has a pair of lead terminals 8a which are connected and fixed by soldering to conductive plates 3a of conductive circuits 2 which are patterned on a circuit board 1, a thermal capacity radiated from the conductive circuits 2 where an over current flows is adjusted by adjusting the conductive plates with the use of an adjusting means, and a trip time of a circuit protective device can be controlled. In case of a single circuit protective device the adjusting means works on adjustment of the width, thickness, and area of each conductive plate which is connected and fixed to each lead terminal. In the case of a plurality of circuit protective devices, the adjusting means works on arrangement of each circuit protective device on a circuit board at the same space, and on setting of each conductive plate which is connected and fixed on the circuit protective device at the same width, thickness, and area, individually.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trip time control structure for a circuit protection device.

[0002]

2. Description of the Related Art In a conductive circuit formed into a pattern on an electronic circuit board, a thermistor having a positive resistance temperature characteristic (hereinafter, referred to as a PTC thermistor) is used as a circuit protection element for blocking overcurrent. The PTC thermistor is a resistor whose zero-load resistance value rapidly increases with a rise in temperature. That is, when an overcurrent flows in the conductive circuit connected to the PTC thermistor, the temperature of the PTC thermistor itself increases due to heat generated in the conductive circuit. PTC with increasing temperature
The resistance value of the thermistor increases rapidly, and the PTC thermistor controls the current value of the current flowing through the conductive circuit. This protects the circuit board.

[0003] The heat radiation of the PTC thermistor itself,
Alternatively, the trip time of the PTC thermistor changes depending on the installation environment of the PTC thermistor. When a plurality of PTC thermistors are used, if the trip times of the PTC thermistors are different, the conductive circuit may be damaged. Therefore, it is necessary to adjust the trip time of the PTC thermistor equally. The trip time refers to a time interval from the moment when the overcurrent starts flowing to the circuit board to the time when the PTC thermistor controls the current value of the overcurrent. Therefore, the resistance characteristic itself of the PTC thermistor is changed to adjust the trip time. That is, the heat radiation amount is adjusted by changing the dimensions of the PTC thermistor itself, or the constituent material of the PTC thermistor is changed.

A PTC thermistor 80 as shown in FIG. 7 is disclosed as an example in which the trip time of the PTC thermistor is changed (Japanese Patent Laid-Open No. Hei 6-137962). The PTC thermistor 80 includes a thermistor body 81 and a material (phosphor bronze plate) 8 having a different thermal conductivity from the thermistor body 81.
2 is thermally coupled. However, PT
Since the number of assembling steps and the number of components in manufacturing the C thermistor 80 increase, there is a problem that the product cost increases.

[0005]

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide a trip time control structure of a circuit protection element capable of easily controlling a trip time without increasing the number of assembly steps and components. I do.

[0006]

In order to achieve the above object, the present invention provides a circuit protection element having a pair of lead terminals fixedly connected to a conductive plate of a conductive circuit formed on a circuit board by soldering. In the above, by adjusting the conductive plate by adjusting means, the amount of heat dissipated from the conductive circuit in which the overcurrent has flown is adjusted, and the trip time control structure of the circuit protection element in which the trip time of the circuit protection element is controlled. Features (Claim 1). Trip time control of a circuit protection element, wherein the adjusting means is means for adjusting the width, thickness and area of each of the conductive plates connected and fixed to the lead terminals for one of the circuit protection elements. It is characterized by a structure (claim 2). The adjusting means arranges each circuit protection element on the circuit board at equal intervals with respect to the plurality of circuit protection elements, and sets the width and thickness of each of the conductive plates connected and fixed to the circuit protection element. And a trip time control structure of the circuit protection element, which is a means for setting the same plate area.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 6 show an embodiment of a trip time control structure of a circuit protection element according to the present invention. In this embodiment, P is used as a circuit protection element.
A case where a TC thermistor is used will be described.

As shown in FIG. 1 and FIG. 2, this trip time control structure connects and fixes a PTC thermistor 4a to a conductive plate 3a of a conductive circuit 2 patterned on a circuit board 1 and trips the conductive plate 3a. A time adjusting means is provided. As shown in FIG. 3, one side 1a of the circuit board 1
Alternatively, a conductive circuit 2 is pattern-formed on both surfaces 1a and 1b. The conductive circuit 2 includes a plurality of conductive plates 3a. Terminal holes 5 are formed in the circuit board 1, and connection holes 6 are provided in the conductive plate 3 a corresponding to the terminal holes 5.

The PTC thermistor 4a has a thermistor body 7 formed of a semiconductor material, and a pair of lead terminals 8a, 8a extending from the inside of the thermistor body 7 to the outside. The pair of lead terminals 8a, 8a
Are arranged on one end face 7a and the other end face (not shown), respectively. Each upper half 8a 'of the lead terminal 8a intersects across the thermistor body 7, and each lower half 8a "is inserted into the terminal hole 5 and the connection hole 6 and connected and fixed to the conductive plate 3a by the solder 9. In the present embodiment, the shape of the thermistor body 7 is elliptical, but a rectangular shape is also possible.

Next, the adjusting means will be described. B) A case in which one PTC thermistor 4a disposed on the circuit board 1 in FIG. 1 is controlled will be described. The adjusting means at this time adjusts the pair of conductive plates 3a, 3a of the conductive circuit 2 to which the pair of lead terminals 8a, 8a are connected, as shown in FIGS. That is, the plate width W, the plate thickness T, and the plate area S of the pair of conductive plates 3a, 3a are adjusted to a desired shape (size).

Thus, the amount of heat generated from the pair of conductive plates 3a due to the overcurrent flowing through the conductive circuit 2 can be adjusted. Therefore, the trip time of the PTC thermistor 4a can be controlled. Because, generally, the conductive circuit 2
(Or heat generated from the conductive plate 3a) and the conductive circuit 2
This is because the trip time of the PTC thermistor 4a is determined by the balance with the amount of heat dissipated from the (or the conductive plate 3a). That is, if the heat is dissipated quickly, it takes time for the heat to reach the PTC thermistor 4a, so that the trip time is delayed. On the other hand, if the heat dissipation is slow, the trip time is shortened because the heat propagation time to the PTC thermistor 4a is not required. In this case, the present invention can be applied to a case where only one of the plurality of PTC thermistors 4b, 4c, and 4d arranged on the circuit board 1 is controlled.

(B) As shown in FIG. 4, a case will be described in which a plurality of PTC thermistors 4b, 4c, 4d arranged on the circuit board 1 are all controlled to the same trip time.
The configuration of the PTC thermistors 4b to 4d is the same as the PT
It is the same as the C thermistor 4a. The adjustment means at this time is
As shown in FIG. 4, the conductive plate 3 fixed to the PTC thermistors 4b to 4d with sufficient spacing D or placed on the circuit board 1 at regular intervals and fixed to the lead terminals 8b to 8d.
The thicknesses T ′ (see FIG. 6), the widths W ′ and the plate areas S ′ (see FIG. 5) of b to 3d are all adjusted to be the same.

The distance D between the PTC thermistors 4b-4d
By placing them sufficiently or at regular intervals,
The thermal effects of the TC thermistors 4b to 4d are prevented.
By setting all the conductive plates 3b to 3d to be the same, the trip times of all the PTC thermistors 4b to 4d can be made the same.

As described in (a) and (b) above, the trip time of the PTC thermistors 4a to 4d in FIGS. 1 and 4 can be changed without any change to the conventional PTC thermistor 80 (see FIG. 7). Can control. Thereby, the PTC thermistors 4a to 4d can be easily and reliably assembled without increasing the number of assembly steps and the number of parts.
~ 4d trip time can be controlled.

[0015]

As described above, according to the first aspect, when an overcurrent flows through the conductive circuit, the conductive plate of the conductive circuit generates heat, and the heat is dissipated from the surface of the conductive plate. Therefore, by adjusting the conductive plate by the adjusting means, the amount of heat dissipated from the conductive plate can be adjusted. Since the trip time is adjusted by adjusting the conductive plate, there is no increase in the number of assembly steps or the number of components when manufacturing the circuit protection element. This makes it possible to easily control the trip time of the circuit protection element without increasing the manufacturing cost of the circuit protection element.

According to claim 2, one circuit protection element,
That is, the width of the conductive plate connected to the lead terminal, the width of the plate, and the number of circuit protection elements arranged only on the circuit board or only one of the plurality of circuit protection elements arranged on the circuit board. The means for adjusting the thickness and the area is the adjusting means.
That is, by increasing or decreasing the width of the conductive plate and increasing or decreasing the thickness thereof, the plate area is increased or decreased. Therefore, the surface area of the conductive plate can be changed to a desired size, and the amount of heat radiated from the conductive plate can be adjusted. Thereby, the trip time of the circuit protection element can be controlled.

According to the third aspect, the width, thickness, and area of each conductive plate connected to the lead terminals of the circuit protection element are all the same for a plurality of circuit protection elements arranged on the circuit board. The means for performing the adjustment is the adjustment means. That is, among the conductive plates of the conductive circuit, only the conductive plates connected to the lead terminals are all made to have the same shape to make the surface area equal. Thereby, the trip times of the plurality of circuit protection elements can all be controlled to be the same. Therefore, damage to the conductive circuit and the circuit board can be prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a trip time control structure of a circuit protection element according to the present invention.

FIG. 2 is a rear view of FIG.

FIG. 3 is a sectional view taken along line XX in FIG. 1;

FIG. 4 is a perspective view when a plurality of PTC thermistors of FIG. 1 are arranged.

FIG. 5 is a rear view of FIG. 4;

FIG. 6 is a sectional view taken along line YY of FIG. 4;

FIG. 7 is a perspective view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circuit board 2 Conductive circuit 3a-3d Conductive plate 4a-4d PTC thermistor (circuit protection element) 8a-8d Lead terminal S, S 'Board area T, T' Board thickness W, W 'Board width

Claims (3)

[Claims] 1. A circuit protection element having a pair of lead terminals connected and fixed by solder to a conductive plate of a conductive circuit formed on a circuit board by patterning. The trip time of the circuit protection element is controlled by adjusting the amount of heat dissipated from the conductive circuit through which the current flows. 2. The method according to claim 1, wherein the adjusting means is means for adjusting the width, thickness, and area of each of the conductive plates connected and fixed to the lead terminals for one of the circuit protection elements. 2. A trip time control structure for a circuit protection device according to claim 1, wherein: 3. The circuit according to claim 1, wherein the adjusting means arranges the circuit protection elements on the circuit board at equal intervals for a plurality of the circuit protection elements, and adjusts each of the conductive plates connected and fixed to the circuit protection elements. 2. A trip time control structure for a circuit protection element according to claim 1, wherein said means is a means for setting the same sheet width, sheet thickness and sheet area.