JPH07147121A - Closed protector with fuse - Google Patents

Abstract

PURPOSE:To provide an closed type protector which is suitable to be used in the inside of a closed container such as an enclosed type electric compressor, etc., and surely shut off an electric circuit even in the case the life of the protector part terminates. CONSTITUTION:Regarding a protector, a closed container is composed of a container 1 made of a metal and a cover plate 2. A thermally responding plate 5 of a bimetal, etc., is put in the inside of the closed container and the protector has a protector part which opens and cuts between a movable contact point 6 and a fixed contact point 7 by the thermally responding plate 5. One end of a functional spring 11 is fixed in the cover plate 2 and the other end is fixed in a fixed rod 8 by a heat sensitive fusing material 12 such as a solder, etc., while resisting against the resilient force of the spring to form an electric circuit. When electric supply to an electric motor is not cut off even in the case somehow the life of the protector part terminates and the contact points are in closed state and it exceeds normal work temperature, the heat sensitive fusing material 12 melts and the functional spring 11 is released from the fixed rod 8 due to the resilient force and the electric circuit is cut off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a hermetic electric compressor and the like, and a protector for protecting the windings of the electric motor from being burnt out when the electric motor is abnormal, and a hermetically sealed member which has an abnormal temperature when the life of the protector is exhausted. Regarding a protector with a sealed fuse that has a fuse that finally cuts the circuit in order to prevent damage to the equipment inside the dome and the high-pressure gas destroying the weakest part of the sealed dome to cause a flame, etc., and a fire accident to occur It is a thing.

[0002]

2. Description of the Related Art Conventionally, a hermetic electric compressor is a refrigeration system in which a refrigerant gas such as freon is highly compressed in a hermetic dome and sent to the outside of the hermetic dome for thermal work and then returned to the hermetic dome. , But its compression pump is driven by an electric motor. If the rotor is restrained due to a load torque that exceeds the motor's rotation torque due to some abnormality, a current several times as much as that during rated operation will continuously flow through the stator winding, and the current will flow near the winding. A motor protector that opens and closes a pair of contacts with a heat-responsive plate such as a bimetal placed repeatedly opens and closes so that the upper temperature limit of the insulation coating of the motor winding is not exceeded, and the load torque falls below the starting torque of the motor. In this case, the contact of the protector intermittently supplies electric power to the motor so that the winding temperature of the motor does not exceed the upper limit of the specified temperature even if the motor is operated or various troubles such as abnormal pressure of the refrigerant gas occur. It is supposed to be done.

[0003]

However, when the protector of the electric motor has been opened and closed a large number of times and the life of the operation has been exhausted, the insulation of the winding of the electric motor is deteriorated when the contacts are in a state of being welded and released. A short circuit and a large current flows from it to a very high temperature inside the closed dome, and the weakest part of the dome, for example, the glass called cluster, which insulates the terminals and keeps them airtight, escapes and a flame blows out. There was a risk of fire.

[0004]

According to the protector with a sealed fuse of the present invention, if the normal protection operating temperature at which the contacts of the protector portion are opened is 180 ° C., the operating temperature of the fuse portion, that is, the temperature for opening the circuit is Higher than 180 ℃, eg 200
The fuse part is installed in the same sealed container as the protector part to quickly detect a dangerous temperature exceeding the limit of temperature rise, which is set to ℃. The temperature-sensitive melting material is arranged so as to form an electric path against the restoring force of the operating spring, and when the temperature rises abnormally, the temperature-sensitive melting material melts to open the operation spring and shut off the electric path. It is designed to have almost no effect of self-heating of the fuse portion due to the current that normally flows through the electric motor, and is configured to have a performance of sensitively responding to the ambient temperature in which the protector with a sealed fuse itself is installed.

[0005]

EXAMPLES Examples will be described below with reference to FIG. This embodiment has a bottomed container 1 formed by drawing an iron plate, as shown in FIG. A lid plate 2 made of a thick iron plate is fixed to the open end, which is the right end in the figure, of the container 1 by a method such as ring projection welding, to form an airtight container as a whole. The internal mechanical parts are housed and assembled before the. The cover plate 2 has two through holes 2A and 2B formed therein, and the lead pins 3A and 3B are electrically insulated from the cover plate 2 and hermetically fixed by a filler G such as glass. The lead pins 3A and 3B are made of nickel alloy in consideration of the thermal expansion coefficients of the cover plate 2 and the filler G. A plate-shaped support body 4 is fixed to the lead pin 3A by welding or the like, and a heat-responsive plate 5 formed by drawing a bimetal or the like into a shallow dish shape near the base of the support body 4 has its fixed end side connected to a connection fitting 5A. It is fixed by a method such as welding. A movable contact 6 made of silver alloy or the like is fixed to the left movable end of the heat responsive plate 5 in the drawing.

On the other hand, a fixed rod 8 is fixed to the lead pin 3B for supporting a fixed contact 7 forming a pair with the movable contact 6. A screw 4A is provided in the screw hole formed near the base of the support body 4.
Are screwed together, and the tip thereof, that is, the lower end in the first figure, is in contact with the connection fitting 5A supporting the heat responsive plate 5. This screw 4
By screwing A downward, the support 4 is thicker and stronger, so that the connection fitting 5A is deformed and fixed to the movable contact 6 at the tip of the heat responsive plate 5 fixed to this tip. The contact pressure between contact 7 can be adjusted,
With this, as is well known, it is possible to prevent chattering at the time of opening and closing the contacts, to perform the snap opening and closing operation, and to adjust the operating temperature.

A lead wire 9 is connected to a portion of the lead pin 3A extending out of the closed container, and a lead wire 10 is connected to the cover plate 2 via a connecting L-shaped metal fitting 2C. The lead pin 3B to which the fixed rod 8 is fixed does not need to be connected to an external circuit and can be short. The protector is entirely wrapped with a heat-resistant insulator called a Mylar tube and mounted on or near the winding of the motor.

In addition, a left end of an operating spring 11 made of, for example, a phosphor bronze plate is provided on a part of a fixed rod 8 which supports a fixed contact 7 in a closed container as an easily melted metal 12 which is a temperature sensitive melting material such as lead and tin. Is soldered, and the right end of the operating spring 11 is fixed to the cover plate 2 by a method such as spot welding. A biasing force is applied to the left end of the actuating spring 11 so that the left end of the actuating spring 11 is in the position shown by the dotted line before being soldered to the fixed rod 8 with the easily meltable metal 12.

As is well known, the lead wires 9 and 10 of this protector are connected in series to a main circuit connecting an electric motor and a power source,
The electric current of the electric motor is from the lead wire 9 to the lead pin 3A → support 4 → connecting member 5A → thermodynamic plate 5 → movable contact 6 → fixed contact 7 → fixed rod 8 → meltable metal 12 → operating spring 11 → cover plate 2
→ L-shaped metal fitting 2C → Pass the electric wire of the lead wire 10.

When the electric motor is operated under normal conditions, each contact of the hermetically sealed fuse protector of this embodiment is kept completely closed, but when the starting torque of the electric motor is less than the load torque or for a long time. When driven and the ambient temperature of the electric motor rises abnormally, the thermal response plate 5 made of bimetal
When the temperature reaches a predetermined temperature, for example 180 ° C., the bending direction is sharply changed as shown by the dotted line in FIG. When the current to the electric motor is cut off for a while and the temperature of the thermal response plate 5 drops to 120 ° C due to natural heat dissipation, the thermal response plate 5 jumps back and the movable contact 6 contacts the fixed contact 7 1 returns to the state indicated by the solid line. Such repetitive operation is performed in the case of normal protection.

Since the sealed type protector is required to be as small as possible from the viewpoint of thermal response, the opening / closing life is often several thousand to 10,000 times, and the life of the protector happens to be for some reason. If the movable contact is exhausted and the fixed contact is closed, the circuit may remain closed even if the normal operating temperature exceeds 180 ° C. In that case, for example, when the temperature reaches 200 ° C., the soldered portion melts and the operating spring 11
The left end of is restored to the position shown by the dotted line from the fixed rod 8 by the repulsive force of the spring, and the electric circuit between the lead wire 9 and the lead wire 10 is opened to safely protect the electric motor etc. as a load from overheating. It is possible to prevent fire and the like. In this case, the fixed rod 8 serves as a shield so that the left end of the actuating spring 11 sufficiently covers the easily melted metal portion to which solder is applied so as to be a shade of the arc due to the normal opening and closing of the contacts 6 and 7 of the protector portion. Is doing.

Next, another embodiment will be described. The protector shown in FIG. 1 is used by being connected in series between the main circuit of the electric motor and the power source, but as shown in FIGS. 2 and 3, for example, in the single-phase induction motor, the main winding LM and When there is an auxiliary winding LA, the auxiliary winding LA is connected in series with the capacitor C to the power source E, and when the auxiliary winding has a higher current density than the main winding, the insulation coating has an abnormal temperature. A heater H provided with an auxiliary winding current inside the protector, which has a relatively large resistance value, is liable to be deteriorated by rising.
There is known a protector which protects the auxiliary winding by connecting the support body 4 or the lead pin 3 which supports the heat responsive plate 5 having the movable contact 6 in this case.
It is made of a material such as a nichrome wire between a portion having the same potential as A and a third lead pin 3C which is electrically insulated from the lid plate 2 by a filling material G such as glass as shown in FIG. The heater H is electrically connected to the heater H, and the heater H is disposed at a position where the heat exchange relationship with the heat responsive plate 5 is improved. The symbols shown in FIG. 2 are the same as the symbols shown in FIG. 1 and represent equivalent substances, and therefore redundant description will be omitted. If the connection is made as shown in FIG. 3, it is possible to prevent the insulation deterioration of the auxiliary winding LA when the current density flowing through the auxiliary winding LA is abnormally high although it is smaller than the main winding LM current.

[0013]

EFFECTS OF THE INVENTION A hermetically sealed protector for an electric motor, which is used under high pressure and in a special atmosphere such as freon gas, operates at a portion relatively distant from the contact portion and shaded by existing parts against direct arc irradiation. By adding a small part consisting of a spring and easily meltable metal, when the contact is closed and the protector has reached the end of its service life, the motor will overheat and the temperature rise will not cause the insulation to break down. Since the current tends to decrease due to the temperature resistance characteristic of the copper wire, it is a very effective safety device that completely eliminates the conventional drawback that the usual current fuse cannot prevent the burnout of the motor winding.

[Brief description of drawings]

FIG. 1 is a vertical sectional view according to an embodiment of the present invention.

FIG. 2 is a side view for explaining another embodiment.

FIG. 3 is an electric circuit diagram of the embodiment shown in FIG.

[Explanation of symbols]

 1: Bottomed container 2: Lid plate 3A, 3B, 3C: Lead pin 4: Support body 5: Thermal response plate 6: Movable contact 7: Fixed contact 8: Fixed rod (shield) 11: Actuating spring 12: Easy melting metal (Thermal melting material) G: Insulating filler

Claims (1)

[Claims] 1. A substantially cylindrical metal container having one end closed and the other end open, and a closed container formed by hermetically welding the open end to a metal lid plate. , A movable contact is fixed to the other end of a heat-responsive plate such as a bimetal electrically insulated from the one end through a support, and the movable contact is deformed by the temperature of the heat-responsive plate. A mechanism for moving by snap opening / closing operation, a mechanism for adjusting the temperature of the snap opening / closing operation of this bimetal, and a fixed contact paired with the movable contact of the bimetal are electrically fixed to the metal container via a fixed rod. The protector part and one end of a conductive actuating spring, which is a part of the electric circuit, are fixed to the cover plate by welding or the like, and the other end of the actuating spring is protected against the restoring force of the actuating spring by a temperature sensitive melting material such as solder. And insulated from the lid plate An electric path is formed by being fixed to the portion, and the temperature-sensitive melting material is melted at a temperature higher than the temperature at which the bimetal is opened by the snap movement, thereby opening the end portion of the operating spring and disconnecting the electric path. A fuse part is housed, and the protector part and the fuse part are connected in series, so that the fuse part is not affected by arc heat generated when the electrical circuit is opened and closed by the normal protective repeated opening and closing operation of the protector part. The operating temperature of the temperature-sensitive melting material of the fuse part is set to a value higher than the normal protection operating temperature of the fuse part, which is relatively distant from the contact part and is housed in a part which is shaded by the shield against the direct irradiation of the arc. Sealed fuse protector characterized by being set.