JP2001023489A - Protection switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protection switch equipped with a bimetal having good response. SOLUTION: A protection switch is structured so that a contact material is adhered to the tip of a movable contact plate while a contact material is adhered to the tip of a stationary contact plate, and on/off are repeated in accordance with the operation of a temp./current sensing element such as bimetal. Therein the movable contact plate is given a smaller section area in the neighbourhood of the contacting position of the temp./current sensing element than the other parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection switch, and more particularly, to a protection switch having a temperature / current detecting element.

[0002]

2. Description of the Related Art In the course of conducting electric power required for a circuit from a power supply battery of a mobile phone, an overcurrent is supplied for the purpose of protecting both the circuit and the battery when an overcurrent flows due to a circuit failure or the like. A current protection switch is provided.

FIG. 5 is a configuration diagram schematically showing the configuration of the protection switch. The base end of the movable contact plate 11 is the case 1
The movable contact plate 11 is fixed to
Is glued. On the other hand, the fixed contact plate 21 is fixed to the case 1 and the fixed contact material 22 is adhered to a position corresponding to the movable contact material 12 at the tip of the movable contact plate 11 at the tip. Further, the first bimetal 31 that deforms at the first temperature (for example, 70 °) and returns at the second temperature (for example, 40 °) straddles the fixed contact plate 21 and the base end of the movable contact plate 11. That is, it is configured to be disposed above the movable contact plate 11. Further, the first bimetal 31 is deformed on the case side (the side opposite to the movable contact plate 11) at a third temperature (for example, 80 °) higher than the first temperature, and is deformed at a third temperature lower than the second temperature. 4 (for example, -1
The second bimetal 32 that returns at 0 °) is arranged in an overlapping manner.

In the above configuration, when the circuit 20 is in a normal state, the contacts are closed as shown in FIG. Here, an abnormality occurs in the circuit 20, and an overcurrent (1 to 3 mA in a normal state) flows from the battery 30,
When the movable contact plate 11, the fixed contact plate 21 and the like have heat, the two bimetals 31 and 32 are naturally heated. When the bimetal 31 reaches the first temperature, as shown in FIG. 4B, the first bimetal 31 deforms and presses the movable contact plate 11 to turn off the contact, When the temperature reaches the second temperature, the first bimetal 31 returns to the original state, and the movable contact plate 11 closes the contacts due to its own elasticity (FIG. 4).
(State of (a)).

This change of state from ON to OFF to ON is repeated until the battery capacity is exhausted unless the overcurrent is too large. However, if the overcurrent is large, the amount of heat generated is large, and the first temperature is reduced. Passed state occurs. Here, when the temperature of the two bimetals becomes higher than the second temperature, the first bimetal 31 and the second bimetal 32 are deformed as shown in FIG.
F, and this state is maintained by the second bimetal 32 even when the temperature falls below the second temperature at which the first bimetal 31 returns. Since the second bimetal 32 is set at a negative temperature as described above, it will not return unless it is brought into a special state (for example, put in a refrigerator).

In place of the second bimetal 32, a part of the movable contact plate 11 is thinned to have a fuse function, and when the second temperature is near, the thinned portion is blown. There are also products.

In the above arrangement, the movable contact plate has elasticity, and when the bimetal returns, there is a cost to return to the position where the contact is turned ON by its own elasticity. Therefore, conventionally, an elastic material such as copper-beryllium has been used for the movable contact plate.

[0008]

In the above prior art, a movable contact having a uniform width is used as a movable contact plate. Therefore, when an abnormality occurs in the circuit and heat generated in the movable contact plate when an overcurrent flows, the heat is dispersed to each part of the movable contact plate, for example, when heat is concentrated at the base end of the movable contact plate. In addition, it takes a long time to operate the bimetal, and heat is accumulated in a case having poor thermal conductivity, causing a phenomenon that the case is broken.

When the case is broken in this way,
Even if the abnormality of the circuit part is restored, the function of the whole product will not be restored unless the protection switch is replaced, which is inconvenient.

[0010]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned conventional circumstances. First, a movable contact plate is adhered to the tip of a movable contact plate and fixed to the tip of a fixed contact plate. It is assumed that a protection switch that repeats ON and OFF in accordance with the operation of a temperature / current detection element such as a bimetal in a state where the contact material is adhered.

In the above configuration, a cross-sectional area of the movable contact plate in the vicinity of a contact position of the temperature / current detection element is smaller than other portions.

As described above, the electric resistance of the portion having a small cross-sectional area becomes higher than that of the other portion of the movable contact plate, and heat is generated in this portion when an abnormality occurs. This results in the immediate transfer of heat to the bimetal contacted by the part, resulting in a diminished response of the bimetal.

[0013]

FIG. 1 is a configuration diagram schematically showing the configuration of a protection switch to which the present invention is applied. Movable contact plate 11
Is fixed to the case 1, and a movable contact material 12 (for example, a silver-nickel alloy) is bonded to a distal end of the movable contact plate 11 (for example, phosphor-bronze). The rear end (the upper left in FIG. 1) of the base end portion attached to the case 1 is led out of the case 1 with the same material as the movable contact plate 11, and one lead for connection to a battery. 113 are formed.

In the above description, the fixing pin 2 is raised at the position where the movable contact 11 is mounted on the lower lid 1a of the case 1, while the fixing pin 2 is inserted and inserted into the upper lid 1b of the case 1 at a position corresponding to the fixing pin 2. A hole 3 is provided, and the fixing pin 2 is inserted into the insertion hole 3 in a state where the fixing pin 2 is inserted into a pin hole 112 provided in a fixing portion 111 behind the base end of the movable contact plate 11. , The lower lid 1a and the upper lid 1b are fixed.

Further, in the above, a constricted portion 110 is formed at the base end of the movable contact plate 11 in the width direction. The constricted portion 110 has a slightly smaller thickness than the other portions (for example, a movable contact plate having a thickness of 0.1 mm is 3 mm thick).
/ 100 mm thinner), and the width of this constricted portion in the longitudinal direction is 0.1 to 0.5 mm. This constricted part 1
By using 10, even if a material having low elasticity (for example, using phosphor-bronze) is used as the movable contact 11, elasticity enough to sufficiently function as a protection switch described later can be secured.

If the above-mentioned movable contact plate 11 is made of a metal (for example, using phosphorus-bronze) having a resistivity enough to allow spot welding, the movable contact plate 11 is used.
And the lead led out of the case 1 from the movable contact plate 11 can be made of the same material metal. That is,
This is because the lead can be directly connected to the terminal of the battery by spot welding.

On the other hand, the fixed contact plate 21 (the same material as the movable contact plate 11) is fixed to the bottom of the case 1 and is fixed at the position of the front end of the movable contact plate 11 corresponding to the movable contact material 12 at the front end. The same material as the movable contact material 12) is adhered. The front end of the fixed contact plate 21 is brought into contact with the base end of a stopper 50 raised in an inverted L-shape from the bottom of the case, and the rear end is drawn out of the case 1 with the same material and used for connection with a battery. The other lead is formed. Also in this case, a metal having a resistivity sufficient to enable spot welding with the battery terminal is fixed to the fixed setting plate 2.
By integrally using the lead 1 and the lead 213, there is no need to separate the fixed setting plate 21 and the lead 213.

The stopper 50 is set at a position lower than the height of the contact member 22 of the fixed contact plate 21 by a predetermined thickness, and when the movable contact member 12 and the fixed contact member 22 do not have the wear described below. The gap having the predetermined thickness is provided between the tip of the stopper 50 and the lower surface of the movable contact member 12 in a state where the two are in contact with each other. That is, the non-contact portion of the movable contact member 12 with the fixed contact member 12 is positioned at the tip of the stopper 50 with the gap having the predetermined thickness.

Further, an arcuate bimetal 41 which is deformed at a first temperature (for example, 70 °) and returns at a second temperature (for example, 40 °) is formed by the arc-shaped legs formed on the case wall (upper side wall in the drawing). )
And the abdomen is disposed so as to abut the movable contact plate 11, and the abdomen of the bimetal 41 presses the movable contact plate 11 due to the elasticity of the bimetal 41 when there is no abnormality. . Thereby, the bimetal 41
Is a contact material 12 at the tip of the movable contact plate 11 and a fixed contact 21
Is in contact with the contact material 22 at the tip of the contact member to form an ON state.

In the above description, the vicinity 116 of the contact portion between the bimetal 41 of the movable contact plate 11 is configured to have a smaller cross-sectional area and a higher resistance than other portions. For example, the surface area of the vicinity 116 of the contact portion is configured to be small, and the width is reduced in plan view, for example, as shown in FIG. Further, as shown in FIG. 3 (b), an impact is applied to the portion to reduce the thickness, reduce the cross-sectional area, and increase the resistance. In the drawing, the width is reduced as described above, and an impact is applied to the center from the back side, and the small protrusion 1 is formed on the front side.
15 is formed, and the compression by the impact reduces the cross-sectional area of this portion to increase the resistance. Therefore, the resistance in the width direction of this portion is increased (the width in the width direction is reduced as described above and the width of the portion that has not been subjected to impact is reduced), and heat is concentrated in this portion.

The tip of the projection 115 directly comes into contact with the abdomen of the bimetal 41. If the small projection 115 is not provided, the abdomen of the bimetal 41 having a small curvature and the movable portion of the bimetal 41 can be used. The contact plate 11 is prevented from forming a contact portion.

In the above configuration, when an abnormality occurs in the circuit 20 and an abnormal current starts flowing from the battery, and the temperature of the bimetal 41 becomes equal to or higher than the first temperature, as shown in FIG. 41 is deformed and no longer contacts the movable contact plate 11, and the movable contact plate 11 opens its contacts by its own elasticity. At this time, the rate of temperature rise in the vicinity 116 of the contact portion with the bimetal 41 having a small cross-sectional area of the movable contact plate 11 becomes the highest, and the reaction of the bimetal 41 becomes faster accordingly. Once the temperature rises below the second temperature, the shape of the bimetal 41 returns to the original state again, and the contacts are turned ON.

As described above, when the abnormal state of the circuit 20 continues, the contacts are turned ON and O between the first temperature and the second temperature.
FF will be repeated. When this repetition is continued, both the movable contact material 12 and the fixed contact material 22 gradually wear, and accordingly, the gap having the predetermined thickness gradually decreases. When the tip of the stopper 50 and the non-contact portion of the movable contact plate 12 are worn until they come into contact with each other, further ON and OFF are not continued, and even when the bimetal 41 is restored, the OFF state is maintained.
Will be maintained.

The bimetal is configured to apply a negative force to the movable contact plate (turn on the contact) in a normal state.
Needless to say, a configuration may be adopted in which the movable contact plate is negatively urged (contacts are turned off) in an abnormal state as in the related art.

As described above, according to the present invention, the rate of temperature rise in the required portion of the movable contact plate can be increased, so that the reaction of the bimetal is accelerated and the function required as a protection switch can be effectively exhibited. There is.

[Brief description of the drawings]

FIG. 1 is a sectional configuration view of the present invention in a normal state.

FIG. 2 is a sectional configuration diagram of an abnormal state.

FIG. 3 is a plan view of the movable contact plate of the present invention.

FIG. 4 is a configuration diagram of a conventional protection switch.

FIG. 5 is a circuit diagram showing a use state of a protection switch.

[Explanation of symbols]

 Reference Signs List 11 movable contact plate 12 movable contact material 21 fixed contact plate 22 fixed contact material 41 bimetal 50 stopper

Claims (1)

[Claims] 1. A state in which a movable contact material is adhered to a tip of a movable contact plate and a fixed contact material is adhered to a tip of a fixed contact plate.
A protection switch in which F is repeated, wherein a cross-sectional area of the movable contact plate near a contact position with the temperature / current detection element is smaller than other portions.