JPH06119858A - Overcurrent protection device - Google Patents

Abstract

PURPOSE:To ensure an easy assembly work, and enable a circuit to be kept in off state, regardless of the deposition strength of a contact, by providing a pair of terminal blocks, a bimetal sheet, a spring terminal, a heater terminal block, a heater and a metal having a low fusion point. CONSTITUTION:When load current flows through a circuit comprising a spring terminal 23, a heater 26, a heater terminal block 24, a metal sheet 27 having a low fusion point, a pair of terminal blocks 15, a bimetal sheet 18 and another pair of terminal blocks 14, the heater 26 and bimetal sheet 18 generate heat by themselves in proportion to an amount of current. Then, upon an increase in current due to the occurrence of overcurrent state, and a rise in the temperature of the sheet 18 up to or above a preset value, the sheet 18 performs reverse operation to cut off the circuit. When a load is cooled and the temperature of the sheet 18 drops to or below a preset value, the sheet 18 is reversed and reset to again close the circuit. In this case, if overcurrent state continues, the sheet 18 is repeatedly reversed and reset, resulting in a fatigue break and a subsequent contact deposition. As a result, power is continuously supplied and the heat of the heater 26 is transferred from the terminal block 24 to the metal sheet 27. Then, the metal 27 is fused to release connection between the blocks 24 and 25, thereby enabling the circuit to be turned off, regardless of contact deposition strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent protection device for a motor for a hermetic compressor used in a refrigerator and a refrigerator.

[0002]

2. Description of the Related Art In recent years, a dual safety function has been demanded from the viewpoint of safety in overcurrent protection measures for compressors used in refrigerators and freezers, and for example, JP-A-2-265135 is widely known. Hereinafter, the above-mentioned overcurrent protection device will be described with reference to the drawings.

5 and 6 show a conventional overcurrent protection device. 5 and 6, 1 is a cylindrical case with a bottom, 2 is a bimetal plate, 3a and 3b are movable contacts, 4, 5
Is a fixed contact plate, 6 is a heater, 7 is a heater terminal plate, 8 is an adjusting screw, 9 is a washer, 10 is a low melting point metal, 1
Reference numeral 1 is a spring, and 12 is a cover. The bimetal plate 2 includes a washer 9, a low melting point metal 10, and an adjusting screw 8.
It is pressed against the fixed contact plates 4 and 5 by and is fixed to the bottomed cylindrical case 1, and is urged upward by the spring 11.

The heater 6 is welded to the fixed contact plate 5 at one end and at the other end to a heater terminal plate, respectively, and is arranged electrically in series with the bimetal plate.

The operation of the overcurrent protection device configured as described above will be described below with reference to FIGS. 5 and 6.

First, the load current from the fixed contact plate 4 to the movable contact 3b, the bimetal plate 2, the movable contact 3a, the fixed contact plate 5,
It flows through each part of the heater 6 and the heater terminal plate 7, and the bimetal plate 2 and the heater 6 self-heat. When the circuit becomes overcurrent, the load current increases, the amount of heat generated by the bimetal plate 2 and the heater 6 increases, and the bimetal plate 2 goes above the set temperature and reverses, and the movable contacts 3a and 3b move to the fixed contact plate 4, 5
Break it further to shut off the circuit.

Next, when the load is cooled and the temperature of the bimetal plate 2 becomes equal to or lower than the set value, the bimetal plate 2 returns to its normal operation,
Close the circuit again. At this time, if the overcurrent state continues due to the motor locking or the like, the bimetal plate 2 repeats reversing and returning, and finally causes fatigue fracture and contact welding. As a result, the temperature of the bimetal plate 2 further rises, the low melting point metal 10 is melted, the washer 9 is separated from the adjusting screw 8 by the urging force of the spring 11, and the bimetal plate 2 is forcibly pushed up to separate the welded contacts. Open the circuit and hold the OFF state.

[0008]

However, the above structure has a problem that the contact cannot be forcibly opened when the welding strength of the contact exceeds the urging force of the spring. .

There is also a problem that the assembly becomes complicated. The present invention solves the above-mentioned conventional problems and is easy to assemble, and the circuit can be OF regardless of the welding strength of the contacts.
An object of the present invention is to provide an overcurrent protection device that can be maintained in the F state.

[0010]

In order to achieve this object, an overcurrent protection device of the present invention comprises a pair of terminal plates integrally molded with a first base, a second base, a spring terminal, a heater and a heater. The terminal plate and the heater terminal plate are welded to each other, and are composed of a spring plate that is normally biased away from one of the pair of terminal plates, and a low melting point metal that connects the spring plate and the pair of terminal plates. The terminal board is connected by two beams, and one of the beams is housed in a unitary molding with the first base. Further, the pair of terminal plates are made of stainless steel and the left and right sides are asymmetrical.

[0011]

With the above-described structure, the present invention is easy to assemble, and the low melting point metal is melted by an abnormal temperature regardless of the welding strength of the contacts to release the contact between the terminal plate and the spring plate, thereby opening the electric circuit. Then the electric circuit can be cut to the safe side.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1, 2, 3, and 4 show an overcurrent protection device according to an embodiment of the present invention. FIG. 1 is a circuit diagram,
2 is a sectional view, FIG. 3 is a perspective view, and FIG. 4 is a plan view of a pair of terminal plates.

In the figure, reference numeral 13 is a first base, which is made of an insulating thermoplastic resin. 14 and 1
Reference numeral 5 denotes a pair of terminal plates, which are connected by two beams 14b and 15b to expose a part and one side of the beam in the first base 13 and project one end to the outside of the base. Is integrally formed with the base 13. Fixed contacts 16 and 17 are welded to the exposed portions of the pair of terminal plates 14 and 15.

Reference numeral 18 is a bimetal plate formed in a dish shape, and snap-actions depending on the temperature. The movable contacts 19 and 20 are welded to the high expansion side of the bimetal plate 18. 21 is an adjusting screw, which is the bimetal plate 1
8 is held in a reversible manner, the movable contact is pressed against the fixed contact, and is fixed to the first base 13.

Reference numeral 22 denotes a second base which is formed of a thermosetting resin having an insulating property and has a protrusion 22a.
Reference numeral 23 denotes a spring terminal, which is a protruding portion 22 of the second base 22.
It is stored in a. 24 is a heater terminal plate, and 25 is a leaf spring, one end of which is welded to the heater terminal plate and is normally urged in a direction away from the terminal plate 15. Reference numeral 26 denotes a heater, one end of which is welded to the spring terminal 23 and the other end of which is welded to the heater terminal plate 24. Reference numeral 27 denotes a low melting point metal which connects the terminal plate 15 and one end of the plate spring.

The pair of terminal plates are made of stainless steel, and the holes 14a and 15a have different hole diameters. The operation of the overcurrent protection device configured as described above will be described below. In the figure, the load current is the spring terminal 2 first.
3, heater 26, heater terminal plate 24, low melting point metal 27 pair of terminal plates 15, bimetal plate 18, pair of terminal plates 14
The heater 26 and the first bimetal plate 18 self-heat in proportion to the magnitude of the current flowing through the circuit. Next, when an overcurrent occurs, the current increases, and when the temperature of the bimetal plate 18 exceeds the set value, the reversal operation is performed to open the contact and break the circuit. Next, when the load is cooled and the temperature of the bimetal falls below the set value, the bimetal reverses and returns to close the circuit again. At this time, if the overcurrent state continues, the bimetal repeats the operation of reversing and returning, and finally the bimetal plate undergoes fatigue fracture and contact welding occurs. The contact welding causes continuous energization, the heat of the heater is transmitted to the low melting point metal 27 through the heater terminal plate 24, the low melting point metal is melted, the leaf spring is displaced, the connection between the terminal plates is released, and the circuit is turned off. Hold.

As described above, according to this embodiment, the circuit can be kept in the OFF state regardless of the contact welding strength.

Further, since one beam is integrally molded in the first base, the base is not deformed by the temperature. Further, since the pair of terminal plates are made of stainless steel, the heat conduction of the heater is delayed and the diameters of the left and right holes are made different so that the temperature of the fixed contact becomes the same value on the left and right, thereby stabilizing the operation of the bimetal.

[0020]

As described above, according to the present invention, the first base made of resin and a part of the first base are exposed and one end of the first base is projected to the outside of the first base. A pair of terminal plates integrally molded with the first base and having fixed contacts on the exposed portion, a thermo-responsive element molded in a dish shape and having a pair of movable contacts at both ends, and a second base made of resin A spring terminal held by the second base and connected to the outside, a heater having one end connected to the spring terminal, and one end outside the second base connected to the other end of the heater. The heater terminal plate that has come out, a leaf spring that is welded to the heater terminal plate and is urged in a direction normally away from one of the pair of terminal plates, and a low connecting member that connects the leaf spring and one of the pair of terminal plates. By having a melting point metal,
The circuit can be kept in the OFF state regardless of the welding strength of the contacts.

Further, by forming the pair of terminal plates from stainless steel and making the left and right sides asymmetrical, the overcurrent protection device can be assembled easily and has excellent performance.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an overcurrent protection device according to an embodiment of the present invention.

FIG. 2 is a sectional view for explaining the operation of the overcurrent protection device according to the embodiment.

FIG. 3 is a perspective view for explaining the operation of the overcurrent protection device according to the embodiment.

FIG. 4 is a plan view of a pair of terminal plates in the example.

FIG. 5 is a sectional view of a conventional overcurrent protection device.

FIG. 6 is a plan view of a conventional overcurrent protection device without a bimetal.

[Explanation of symbols]

 13 First Base 14, 15 Pair of Terminal Plates 18 Bimetal Plate 21 Adjusting Screw 22 Second Base 23 Spring Terminal 24 Heater Terminal Board 25 Leaf Spring 26 Heater

Claims (3)

[Claims] 1. A first base made of resin, and a part of the first base is exposed in the first base and one end of the first base is projected to the outside of the first base to be integrally molded with the first base. And a pair of terminal plates each having a fixed contact on the exposed portion, a thermo-responsive element formed in a dish shape and having a pair of movable contacts at both ends, a second base made of resin, and the second base. A spring terminal connected to the outside, a heater having one end connected to the spring terminal, and a heater terminal plate connected to the other end of the heater and having one end outside the second base; An overcurrent composed of a leaf spring welded to the heater terminal plate and urged so as to be normally separated from one of the pair of terminal plates, and a low melting point metal connecting the plate spring and one of the pair of terminal plates. In the protective device, connect the pair of terminal plates with two beams. An overcurrent protection device characterized in that one of the beams is integrally molded with the first base while being stretched. 2. A resin-made first base, and a part of the first base is exposed in the first base and one end of the resin is integrally formed with the first base so as to project outside the first base. And a pair of terminal plates each having a fixed contact on the exposed portion, a thermo-responsive element formed in a dish shape and having a pair of movable contacts at both ends, a second base made of resin, and the second base. A spring terminal engaged to the outside and connected to the outside, a heater having one end connected to the spring terminal, and a heater terminal plate connected to the other end of the heater and having one end outside the second base. A plate spring welded to the heater terminal plate and urged so as to be normally separated from one of the pair of terminal plates; and a low melting point metal connecting the plate spring and one of the pair of terminal plates. In the current protection device, the pair of terminal plates are made of stainless steel. An overcurrent protection device characterized by being configured. 3. A resin-made first base, and a part of the first base is exposed in the first base, and one end of the first base is projected to the outside of the first base to be integrally molded with the first base. And a pair of terminal plates each having a fixed contact on the exposed portion, a thermo-responsive element formed in a dish shape and having a pair of movable contacts at both ends, a second base made of resin, and the second base. A spring terminal engaged to the outside and connected to the outside, a heater having one end connected to the spring terminal, and a heater terminal plate connected to the other end of the heater and having one end outside the second base. A plate spring welded to the heater terminal plate and urged so as to be normally separated from one of the pair of terminal plates; and a low melting point metal connecting the plate spring and one of the pair of terminal plates. In the current protection device, the pair of terminal plates are asymmetrical to each other. An overcurrent protection device characterized in that