JPH07201262A - Overcurrent protector - Google Patents

Abstract

PURPOSE:To provide an overcurrent protector with double protecting capabilities to completely prevent the burning of an electric compressor in a simple structure. CONSTITUTION:During overload, the first bimetal armature 5 is operated with the heating of a heater 4 due to an overcurrent or the temperature rise of an electric compressor to cut off a connected armature 3A for disconnecting a current to the electric compressor, so that the electric compressor is protected. When the life of the first bimetal armature 5 runs out and its function decays, the second bimetal armature 12 is actuated at the second temperature or higher than the first temperature at which the first bimetal armature 5 is actuated, to cut off a current supply circuit. In this way, complete protection is carried out not to burn the electric compressor on account of a continuous overcurrent.

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 protecting an electric compressor used in a refrigerator or a small air conditioner from its overloaded state or locked state, that is, burnout due to overcurrent.

[0002]

2. Description of the Related Art Conventionally, in order to protect an electric compressor from its overcurrent state, a switch contact piece serially inserted in a circuit is closely attached to a body case of the electric compressor to detect a temperature. Further, there is provided an overcurrent protection device which opens and closes by using a bimetal contact piece which is operated by the heat of the heater which generates heat in accordance with the applied current.

7 to 10 show the construction and protection circuit of the conventional overcurrent protection device. Explaining in accordance with the above-mentioned drawings, the overcurrent protection device 1 includes a pair of fixed terminals 2a and 2b provided in a resin case 1a and fixed terminals 2a and 2
A connecting piece 3 for connecting between b, a heater 4 which is connected in series with the connecting piece 3 and through which a load current, that is, an electric compressor current flows, and a heater 4 which is mounted above the heater 4 so as to face the heater 4, It is composed of a bimetal contact piece 5 which is curved and is turned upside down in response to heat from the heater 4 or a temperature rise of the electric compressor itself, and which operates to disconnect the connection contact piece 3. That is, the connecting piece 3 and the heater 4
And the bimetal contact piece 5 form a current supply circuit. Reference numeral 5a is an operating projection provided at the center of the bimetal contact piece 5. The bimetal contact piece 5 is attached to both ends of the stepped portion 9a formed on the mounting member 9 of the fixed terminal 2a and the stepped portion 1b formed on the case 1a. The connecting contact piece 3 is provided so that a part of the connecting contact piece 3 is fixed to the fixed terminal 2a and the other end is brought into contact with and separated from the other fixed terminal 2b. The fixed terminal 2b is not shown but is one end of the electric compressor. The heater 4 is connected to one end of a power source (not shown) via the connection terminal 8.

Here, during normal operation of the electric compressor, since the load current is below the set value, the amount of heat generated from the heater 4 is not so large as to reverse the bimetal contact piece 5 as shown in FIG. Since the case temperature rise does not receive the amount of heat enough to reverse the operation of the bimetal contact piece, the connection piece 3 is closed and the electric compressor is in the power supply state.

However, if the electric compressor is overloaded, or if it is brought into a starting failure or lock state, the temperature of the electric compressor rises, the amount of heat received by the bimetal contact piece 5 increases, and an excessive current of a set value or more is applied. As a result, the amount of heat generated by the heater 4 increases, the bimetal contact piece 5 reverses as shown in FIG. 9, disconnecting the connecting contact piece 3 from the fixed terminal 2b, and temporarily disconnecting the electric compressor from the power source and burning it. It prevents accidents.

[0006]

As described above, the bimetal contact piece operates to protect the electric compressor at the time of overload, but the bimetal contact piece is repeatedly rotated in the forward and reverse directions for a long period of time. And repeated (tens of thousands of ON-OFF operations)
The life of the bimetal contact piece has expired, and in the above-mentioned conventional device, the force that the bimetal contact piece pushes to separate the connecting contact piece cannot be obtained, and the protective circuit fails in its protective operation, resulting in continuous energization and burnout of the electric compressor. There was a problem that led to etc.

The present invention has been made in view of the above problems, and when the main first bimetal contact piece is broken due to its service life or the like and loses its protective function, the second bimetal contact piece operates instead of the first bimetal contact piece. It is an object of the present invention to provide an overcurrent protection device which has one side and protects an electric compressor from a burning accident or the like.

[0008]

DISCLOSURE OF THE INVENTION The present invention relates to an overcurrent protection device which is inserted in series between an electric compressor and a power source, and an electric heater through which a current supplied to the electric compressor flows, and the electric heater. A first bimetal contact piece that is thermally coupled to the heater and that interrupts a current supply circuit to the electric compressor at a first temperature or higher;
And a second bimetal contact piece that shuts off the current supply circuit to the electric compressor at a second temperature higher than the above temperature.

Further, according to the present invention, all or part of the current supply circuit is constituted by the second bimetal contact piece.

[0010]

When the electric current flows into the electric compressor abnormally, the heater heats up, and when the electric compressor case temperature rises above the first temperature, the first bimetal contact piece opens,
The current supply circuit to the electric compressor is cut off and protected.
When such a normal protection operation of opening and closing the first bimetal contact piece is repeated and the first bimetal contact piece has expired and the open circuit operation is stopped, an excessive current flows in the electric compressor. It will be the worst situation to continue.

In such a case, the heat of the heater or the case temperature of the electric compressor further rises, and the second temperature higher than the first temperature is reached.
When the temperature reaches or exceeds, the second bimetal contact piece opens to open the current supply circuit to cut off the overcurrent to the electric compressor and reliably prevent accidents such as burning. Further, the second bimetal contact piece also serves as a current supply circuit or constitutes a part thereof, so that the number of components can be reduced and a circuit connection that is not complicated can be realized.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The same or equivalent components as those of the conventional device shown in FIGS. 7 to 10 are designated by the same reference numerals.

Reference numeral 11 denotes a conductive piece which is fixedly attached to one fixed terminal 2a and extends horizontally. Reference numeral 12 is a second bimetal contact piece connected and fixed to the tip of the conductive piece 11 by welding or the like. The contact portion 13 at the tip of the second bimetal contact piece 12 has the other fixed terminal 2
It is usually in contact with b as shown in FIG. Therefore, the conductive piece 11 and the second bimetal contact piece 12 connected to the conductive piece 11 form a connecting piece 3A corresponding to the connecting piece 3 of the conventional device.

Here, the second bimetal contact piece 12 is shown in FIG.
As shown in FIG. 3, the operating temperature (second temperature) t2 when changing from the fixed contact 2b to the upward warped state is as shown in FIG.
Operating temperature (first temperature) t when reversing as shown in
The temperature is set to be considerably higher than that of 1. Therefore, the second bimetal contact piece 12 is designed to function only when the normal first bimetal contact piece 5 is inoperative.

Therefore, normally, the second bimetal contact piece 12 is in the state as shown in FIG. 1, and the contact portion 13 thereof is the fixed contact 2.
2 and the circuit is in the situation shown in FIG.
The circuit between a and 2b is closed.

When the normal protection operation by the first bimetal contact piece 5 is performed, the first bimetal contact piece is generated due to heat generation due to energization of the heater 4 with an excessive current and due to the temperature rise of the electric compressor itself. 5 responds to heat and flips upward. As a result, the operating projection 5a of the first bimetal contact piece 5
The conductive piece 11 has its tip bent upward as shown in FIG. 3, and the second bimetal contact piece 12 is fixed to the fixed contact 2b.
The fixed contact 2 is separated from the circuit and becomes a state as shown in FIG.
Open circuit between a and 2b. That is, the current supply circuit to the electric compressor is cut off.

When the temperature of the first bimetal contact piece 5 is lowered after a certain period of time, the second bimetal contact piece 12 is restored so as to come into contact with the fixed contact 2b again. If the energized current is returned to the preset value or the temperature rise of the electric compressor is not high after the recovery, the energized state is maintained.

In this way, the first bimetal contact piece 5 reverses every time when an overload or a lock state occurs, so that the electric compressor is temporarily cut off from the power source to protect it.

However, when this repetitive operation is repeated and the life of the first bimetal contact piece 5 is exhausted, even if it is reversed, it is not possible to obtain a degree of inversion enough to open the second bimetal contact piece 12, or It will not be reversed at all.

In such a state, the fixed contacts 2a, 2
The electric compressor continues to operate while the circuit b is closed, and an excessive load current continues to flow through the heater 4. Therefore, the heater 4
When the ambient temperature in which the second bimetal contact piece 12 exists reaches or exceeds the second temperature t2, which is higher than the first temperature t1, as shown in FIG. The piece 12 is curved and separated from the fixed contact 2b. Further, as the operation of the electric compressor continues, the temperature rise also rises abnormally, and when the second bimetal contact piece 12 reaches the operating temperature (second temperature) t2 or more, it also bends so as to open. It operates to shut off the electric current supply circuit to the electric compressor and stop the operation of the electric compressor to protect the electric compressor doubly to prevent accidents such as burning.

Here, the second bimetal contact piece 12 has its reset temperature set as low as, for example, about -50.degree.
In a normal environment, once the second bimetal contact piece 12 operates, the second bimetal contact piece 12 does not return (contact with the fixed contact 2b) but keeps the protection circuit open.

In the embodiment, the second bimetal contact piece 12 is used.
Is partially provided at the tip of the conductive piece 11 and is connected to the connecting piece 3A.
However, it is also possible to construct the connecting contact piece 3A entirely by the second bimetal contact piece 12 and bridge it between the fixed terminals 2a and 2b. In other words, it is sufficient that the current supply circuit (substantially, the switch contact piece portion 3A) is entirely or partially configured by the second bimetal contact piece 12.

[0023]

As described above, according to the present invention, when the life of the first bimetal contact piece that normally protects the electric compressor is exhausted, the temperature of the heater and the electric compressor rises due to continuous energization. Since the second bimetal contact piece that disconnects the current supply circuit to the electric compressor by receiving heat from the case is provided, the electric compressor is doubly protected against overload and overcurrent conditions in the locked state. And is a perfect overcurrent protection device. Therefore, the electric compressor can be used safely for a long time and can be made economical. The overcurrent protection device is structurally simple.

Further, by forming all or part of the current supply circuit for the electric compressor by the second bimetal contact piece, the number of parts can be reduced, the assemblability can be facilitated, and the cost can be reduced. The effect such as being able to be achieved can be obtained.

[Brief description of drawings]

FIG. 1 is a side sectional view of an overcurrent protection device of the present invention in a normal state.

FIG. 2 is an internal circuit diagram of the overcurrent protection device in the state of FIG.

FIG. 3 is a side cross-sectional view of the overcurrent protection device showing a state during a normal protection operation.

4 is an internal circuit diagram of the overcurrent protection device in the state of FIG.

FIG. 5 is a side sectional view of the overcurrent protection device when the safety protection function is activated.

FIG. 6 is an internal circuit diagram of the overcurrent protection device in the state of FIG.

FIG. 7 is a side sectional view showing a state of a conventional overcurrent protection device in a normal state.

FIG. 8 is an internal circuit diagram in the state of FIG.

FIG. 9 is a side cross-sectional view of a conventional overcurrent protection device showing an aspect when a normal protection operation is performed.

10 is an internal circuit diagram of the overcurrent protection device in the state of FIG.

[Explanation of symbols]

 1 Overcurrent protection device 2a, 2b Fixed terminal 3, 3A Connection contact piece 4 Heater 5 Bimetal contact piece 12 Second bimetal contact piece

Claims (2)

[Claims] 1. An overcurrent protection device which is inserted in series between an electric compressor and a power source, wherein an electric heater through which a current supplied to the electric compressor flows and a heater which is thermally coupled to the electric heater are provided. To the electric compressor, which is thermally coupled to the first heater and the first bimetal contact piece that shuts off the current supply circuit to the electric compressor at a temperature of 10 ° C or higher. And a second bimetal contact piece for interrupting the current supply circuit. 2. The overcurrent protection device according to claim 1, wherein all or part of the current supply circuit is constituted by the second bimetal contact piece.