JPH0547278A - Thermally actuated switch - Google Patents

Abstract

PURPOSE:To remove a fixed contact from a conductive pin and break a cable way securely in a thermally actuated switch using a thermally actuated plate in case fusion of a contact or the like occurs. CONSTITUTION:A closed container is composed of a cover 1 of metal, and a cover plate 5 welded at its aperture end surface, and a conductive pin 7 is electrically insulated and fixed gas-tightly to the cover plate 5. A fixed contact 8 is fixed to the conductive pin 7 by an easy-to-fuse material 9 which loses its fixture force at a higher temperature than an operation temperature of a thermally actuated plate 2. A spring 10 having a force to get the fixed contact 8 apart from the conductive pin 7 is also provided. One end of the thermally actuated plate 2 which operates at a predetermined temperature is fixed to the inside of the closed container, and a movable contact 3 is provided at the other end. The movable contact 3 and the fixed contact 8 are disposed to get in contact with or apart from each other. For emergency such as fusion of the contact, the easy-to-fuse material 9 loses its fixture force to get the fixed contact 8 apart from the conductive pin 7 to break a cable way securely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hermetic compressor for a refrigerator and a heat-actuated switch for protecting an electric motor from overheating and burnout used in this kind, and particularly, the life of the heat-actuated switch is exhausted. The present invention relates to a hermetically sealed heat-actuated switch that can reliably shut off the electric circuit when an abnormal temperature is reached.

[0002]

2. Description of the Related Art Conventionally, a hermetic electric compressor is a refrigerating cycle in which a refrigerant gas such as CFC is compressed by a compression pump in a hermetic container and sent to the outside of the hermetic container for heat exchange and then returned to the hermetic container again. , But the compression pump is driven by an electric motor. If a load torque greater than the motor rotation torque is generated and the rotor is restrained due to some abnormality, the stator windings will continue to flow several times as much current as during rated operation. A thermal response switch that opens and closes a pair of contacts with a thermal response plate such as a bimetal placed near the windings repeatedly opens and closes so that the upper temperature limit of the insulation coating of the motor does not exceed the load torque. When the torque falls below the starting torque of the motor, the contact point of the thermal response switch is set so that the winding temperature of the motor does not exceed the upper limit of the predetermined temperature even if the motor is operated or various troubles such as abnormal pressure of the refrigerant gas occur. The electric power is supplied to the electric motor intermittently.

[0003]

However, when the thermal response switch of the electric motor is opened and closed a large number of times and the life of the operation is exhausted, when the contact remains welded and the current continues to flow to the electric motor, The insulation of the winding deteriorates due to heat generation, which causes a large short-circuit current to flow to an extremely high temperature inside the sealed container. The weakest part of the container, for example, a glass called a cluster, insulates the terminals and keeps them airtight There was a danger that a fire would occur due to the flame coming out from the part that is being operated.

The heat-actuated switch of the present invention is used when an abnormal current continues to flow to the electric motor and the temperature in the hermetically sealed container becomes abnormally high, when the contact cannot be opened due to the end of its operating life. Is to provide a heat-responsive switch capable of surely cutting off the electric circuit before a dangerous situation such as a flame blowing out from a closed container.

[0005]

The cover constituting one side of the container of the heat-responsive switch of the present invention has a substantially arcuate portion in the middle and both ends are formed into a shape close to a spherical surface by molding a metal plate by pressing or the like. It has a long dome shape made of metal, and has a cover having a slightly flat fixing portion on one spherical portion and a small protrusion on the other spherical portion. The lid plate that constitutes the other side of the container is a metallic lid plate whose planar shape at least includes the end surface shape of the cover so as to be welded to the open end surface of the cover. The heat-actuated switch of the present invention is composed of a hermetically sealed container constituted by these. The cover plate is provided with a through hole on one side in the longitudinal direction, and the conductive pin is airtightly fixed to the cover plate through the cover plate by an electrically insulating filler such as glass, and both ends thereof are hermetically sealed. It projects to the inner side and the outer side by a predetermined length.

One end of the metal support is fixed to the inside of the closed container in the flat portion of the cover, and the other end is formed of a metal plate, such as a bimetal, which is deformed in response to a change in temperature in a substantially rectangular shape. One end of the heat responsive plate that changes the bending direction in a snap manner according to different temperatures is fixed by drawing the center of the plate into a shallow dish. A movable contact made of an electric contact material such as silver or a silver alloy is fixed near the free end of the heat responsive plate, that is, on the side where the position is changed when the snap-reverse-return operation is performed. It is arranged so as to come into contact with the fixed contact.

One end of the fixed contact is fixed along the longitudinal direction of the cover plate to the inner end of the closed container of the conductive pin with a fusible material, and the other end is fixed with a contact material such as silver or silver alloy. As described above, the contact material portion is always in contact with the movable contact described above.

A protruding portion thinner than the diameter of the conductive pin is provided at the inner end of the conductive pin, that is, the fixed end with the fixed contact, and the fixed contact with the conductive pin has the diameter as described above. A through hole is provided that is larger than the diameter of the protrusion and smaller than the diameter of the conductive pin. The fixed contact has a projection of a conductive pin inserted in its mounting hole, and the temperature at which the melting or fixing force decreases is set to a temperature higher than the operating condition of a normal thermal response switch, that is, a temperature higher than the operating temperature of the thermal response plate. It is fixed by the easily melted material.
At this time, the fixed contact is configured to cut off the electrical connection with the conductive pin at least when the easily meltable material is melted or the fixing force is reduced by a spring, a shape memory alloy, or the like. Further, if the positional relationship between the conductive pin and the fixed contact can be surely obtained by a positioning jig or the like at the time of fixing, the protruding portion of the conductive pin and the mounting hole for the fixed contact are not always necessary.

After the cover plate and the long dome-shaped cover are airtightly fixed to each other at the opening end surface by welding or the like, the fixed end of the heat responsive plate supporting member to the cover is displaced by the deformation of the cover to move. This is a thermo-responsive switch capable of calibrating the snap operating temperature of the thermo-responsive plate in which the movable contact separates from the fixed contact by adjusting the contact pressure between the contact and the fixed contact.

With the above-mentioned construction means, during normal operation of the heat responsive switch, for example, when the rotor of the electric motor is restrained, the temperature of the heat responsive plate is increased due to the increase of the current and the ambient temperature of the heat responsive switch. As the temperature rises to the operating temperature, the contact opens and closes due to the operation, and the electric circuit is opened and closed to protect the motor from burnout, and when the cause of rotor restraint is removed, current and switch ambient temperature are removed. Returns to normal and the heat responsive plate maintains the contact state of the contacts so that the electric motor can return to the normal continuous energization state. Further, when the restraint of the rotor of the electric motor is not removed, the operation of the switch for protecting the electric motor from burning is continued for a long period of time, so that the life of the thermal reaction plate of the switch or the contact ends and the welding of the contact, etc. If the electric circuit cannot be opened due to melting, the sticking force decreases due to melting of the easily meltable material, and the fixed contact is separated from the conductive pin due to the repulsive force of the spring, etc., so that the electric circuit is reliably cut off and the motor burns out. It is possible to reliably prevent the occurrence of fire.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The cover 1 made by drawing an iron plate with a press has a long dome shape with a semicircular center part on both sides and a substantially flat part on one side. It has a portion 1A and the spherical portion has a small protrusion 1B. Inside the cover 1, there is a heat responsive plate 2 made of bimetal or the like, a movable contact 3 is fixed to the movable end side by a method such as spot welding, and on the other hand, a fixed metal plate is formed on the fixed end side. It is fixed to one end of the produced support body 4 by a method such as spot welding. The other end of the support 4 is fixed to the inner surface of the cover 1 at a fixing portion 1A of the cover 1 by a method such as spot welding.

A cover plate 5 formed by forming a thicker iron plate than the cover 1.
Has a through hole 5A near its center.
A conductive pin 7 is hermetically fixed to 5A by a well-known hermetic seal such as a compression type by an electrically insulative filling material 6 such as glass in consideration of a thermal expansion coefficient. Further, a fixed contact 8 having a contact material portion 8A made of silver alloy or the like adhered and fixed to one end of the conductive pin 7 is provided at a predetermined position in a state substantially orthogonal to the conductive pin 7 as shown in the drawing.
It is fixed by the easily meltable material 9 that reduces the fixing force at a predetermined temperature.

The fixed contact 8 is provided with a small hole 8C,
On the lower side of this small hole 8C shown in FIG. 1, an insulator 11 made of an electrically insulating material such as ceramic is fitted and fitted with its protrusion 11A. A leaf spring 10 is inserted between the insulator 11 and the cover plate 5 for holding a force in a direction to push them open, that is, a force in a direction to separate the fixed contact 8 from the conductive pin 7. A small hole 10A is formed in the center of the leaf spring 10, and the position of the leaf spring is also determined by inserting the protrusion 11B of the insulator 11 into the hole.

A cover plate 5 is hermetically sealed to the open end 1C of the cover 1 by a method such as ring projection welding.

The fixing portion between the conductive pin 7 and the fixed contact 8 will be described in more detail. A tapered fixing projection 7A is provided at the tip of the conductive pin 7 inside the container, and the maximum diameter of the fixing projection 7A is that of the conductive pin 7. The diameter of the conductive pin 7 is smaller than the diameter, and the conductive pin 7 has a shoulder at the boundary with the fixed protrusion 7A.
Has 7B. Further, a mounting hole 8B whose diameter is set to be larger than the maximum diameter of the fixed projection 7A and smaller than the diameter of the conductive pin 7 is provided on the side of the fixed contact 8 which becomes the fixed end. The fixed contact 8 has the fixing projection 7A in the mounting hole 8B.
Is inserted and positioned so as to abut against the shoulder portion 7B, and is fixed by the easily meltable material 9 in a state substantially orthogonal to the conductive pin 7.

In addition to this, a method for positioning using a mounting jig, for example, the cover plate 5 having the conductive pins 7 is mounted on the first jig, and the fixed contact 8 is mounted on the second jig. If the mounting is performed and the first jig and the second jig are abutted to each other so that they are positioned in a predetermined positional relationship and are fixed with the easily meltable material, the fixing projections 7A and the mounting holes 8B are not always necessary. It is easy to understand that this is not the case.

Further, the heat responsive plate 2 is, for example, 300 so that the reversal operation temperature and the return operation temperature do not change for a long time.
It is preferable to go through an aging step of allowing the material to stand in a constant temperature oven at ℃ for a predetermined time and then returning it to room temperature. Before the aging step, the heat responsive plate 2 and the support 4 are joined by a method such as spot welding. Already fixed. The heat at the time of spot welding the support 4 at the fixed portion 1A of the cover 1 instantaneously and locally becomes a high temperature, but substantially the heat at the time of this spot welding is applied to the heat responsive plate 2 before aging. Care is taken not to diminish the effect of the process. In addition, in the present invention, when solder or the like is used as the easily meltable material, the application part has a structure in which the fixed contact 8 is fixed to the conductive pin 7, so that the heat of the soldering iron or the like is completely removed from the heat responsive plate. It has no effect.

The operating temperature of the heat responsive plate 2 is calibrated so that it reverses at a predetermined temperature, for example, 130 ° C., by changing the contact pressure between the fixed contact 8 and the movable contact 3. This is possible by deforming the flat portion 1A of 1. That is, since the heat responsive plate 2 is provided via the support 4 and the movable contact 3 is provided at the tip thereof, a slight displacement at the flat portion 1A is greatly expanded as the displacement of the movable contact 3. Therefore, a wide range of change in the contact pressure can be made possible by the deformation in a range that hardly affects the pressure resistance of the cover 1. The small protrusions 1B are formed in consideration of the amount of protrusion so that the distance between the contacts is regulated when the heat responsive plate 2 is bent at a predetermined temperature and the bending direction is reversed to the direction shown by the dotted line. ..

Next, the operation of this thermoresponsive switch will be described. The electric current flowing through the electric motor is the conductive pin 7 and the cover plate 5.
The electric current of the electric motor is supplied to the electric path of the conductive pin 7-fixed contact 8-movable contact 3-thermo-responsive plate 2-support 4-cover 1-cover 5 if the motor is connected through the electric circuit. When the current flowing through the electric motor is a normal operating current including a large current for a short time at the time of start-up, the heat responsive plate 2 is heated by the total heat generation amount of the electric circuit, but its temperature is a predetermined operating temperature, for example.
The electric motor continues to operate without reaching 130 ° C.

When some abnormality occurs and the load of the electric motor increases and the current during operation continues to increase, or when the operating current is normal but the internal refrigerant gas has an abnormally high temperature. The temperature in the closed housing in which the heat-responsive switch is installed, that is, the ambient temperature of the switch is quickly transmitted, and the heat-responsive plate 2 in the switch changes its bending direction by the sudden reversal operation and moves as shown by the dotted line in FIG. The contact 3 is separated from the fixed contact 8 to cut off the electric current of the electric motor. Further, when the torque of the electric motor is less than the load torque, the rotor is in a restrained state, and the excessive current at the time of starting continues for a time longer than the time required for normal starting, for example, 2 seconds to 3 seconds. And the temperature of the heat responsive plate 2 reaches the above-mentioned 130 ° C., and the movable contact 3 is separated from the fixed contact 8 by the sudden reversal operation to interrupt the electric current of the electric motor. When it is naturally cooled in that state and reaches 90 ° C., for example, the thermal responsive plate 2 changes its curving direction by a sudden jump reversing operation to bring the movable contact 3 and the contact material portion 8A of the fixed contact 8 into contact again.

In the above operation, when the cause of the abnormality that has occurred in the electric motor is not eliminated and, for example, the rotor is kept in the restrained state, the thermal response plate 2 of the switch repeats the reversing operation and the returning operation to open and contact the contacts. Finally, due to the fatigue of the heat responsive plate and the welding of the contacts, the electric circuit may not be opened even when the temperature reaches 130 ° C. As a result, the temperature inside the electric motor and the inside of the switch further rises to an emergency state, and eventually the temperature around the easily meltable material 9 reaches, for example, 150 ° C. at which its melting or sticking force decreases, and the sticking force of the easy melting material 9 decreases. Release the restraint between the mounting hole 8B on the fixed contact 8 and the fixed protrusion 7A on the conductive pin 7. At this time, the fixed contact 8 is the leaf spring 10 placed on the cover plate 5 via the insulator 11.
Since it has a restoring force, it is separated from the conductive pin 7 as shown in FIGS. 4 and 5, and surely cuts off the electric path.

In the present embodiment, the mechanism for separating the fixed contact from the conductive pin is a leaf spring, but the shape is not limited to the leaf spring, and the fixed contact can be separated from the conductive pin. Clearly, Also,
This spring can be replaced with a shape memory alloy whose transformation temperature is selected so as not to deform the fixed contact fixing portion during normal operation of the electric motor. Further, it can be easily understood that the insulator 11 is unnecessary by using an electrically insulating material such as ceramics or heat resistant resin for the spring itself. Further, as the easily meltable material 9, in addition to solder which is an alloy of lead and tin, tin which is known as an easily meltable alloy,
If several kinds of lead, bismuth and cadmium are mixed and mixed at an appropriate ratio, it is possible to select the melting point at a temperature lower than that of solder. In addition to this, paying attention to the heat deformation temperature of synthetic resin, etc., the shape before heat deformation can be applied as a fixing force, and it can be used as an easily meltable material whose fixing force is lowered by starting thermal deformation. Is easy to understand.

[0023]

INDUSTRIAL APPLICABILITY As described above, the present invention provides a heat-responsive switch having a pressure resistant container structure suitable for immediately responding to an abnormal overheat of an electric motor or a refrigerant gas in a hermetically sealed electric compressor. When an abnormality occurs in the motor, when the normal thermal switch is activated, the thermal plate reverses-returns to interrupt the current-energizes the motor and causes a disadvantage such as burning due to abnormal heat generation in the winding of the motor. You can prevent it,
When the cause of the abnormality is removed, it is possible to return to the normal continuous energization state.

Further, when the electric motor continues to malfunction and the switch is exhausted due to fatigue of the heat responsive plate and the contacts are welded, the easily meltable material that fixes the fixed contact and the conductive pin is melted. Or, the fixing force is lost, and the fixed contact and the conductive pin are electrically separated by the opening mechanism such as the spring, and the electric circuit can be surely turned off, and it is possible to prevent the motor from burning or fire. ..

Further, even when solder or the like is used as the low temperature melting material, the fixed contacts are fixed by the solder or the like, so that the heat of the soldering iron or the like does not affect the heat responsive plate. ..

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of a thermoresponsive switch of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of the thermoresponsive switch of FIG.

FIG. 3 is a cross-sectional view taken along the line BB of the thermoresponsive switch of FIG.

FIG. 4 is a vertical cross-sectional view showing an emergency state of the thermoresponsive switch of FIG.

5 is a cross-sectional view taken along the line CC of FIG.

[Explanation of symbols]

 1: Cover 1C: Open end 2: Thermal response plate 3: Moving contact 4: Support 5: Lid plate 5A: Through hole 6: Filling material 7: Conductive pin 8: Fixed contact 9: Easy melting material 10: Spring 11: Insulator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isao Touhou 178 North Kasumigaoka-cho, Owariasahi-shi, Aichi (72) Inventor Hideki Ozeki Minamiyama, Fuyama-cho, Niwa-gun, Aichi 40-2 Oyama Nishi 40

Claims (4)

[Claims] 1. A closed container comprising a metal long dome-shaped cover and a lid plate welded to an open end surface of the lid, and a through hole is provided at an appropriate position of the lid plate, and the through hole is made of glass. A conductive pin penetrates through the lid plate and is airtightly fixed by an electrically insulating filling material such as that, and a fixed contact is fixed at one end along the longitudinal direction of the conductive pin protruding to the inside of the closed container. The inside of the closed container of the cover is made of a material such as a bimetal that deforms in response to changes in temperature, and is formed in a substantially rectangular shape. One end of the heat responsive plate that changes the bending direction by snapping is fixed, and the other end of the heat responsive plate, that is, the end that moves during the snap movement, is provided with a movable contact, and the movable contact makes contact with or opens the fixed contact. To separate In the disposed heat-responsive switch, the fixing portion between the conductive pin and the fixed contact is fixed by a meltable material that melts or loses a fixing force at a temperature higher than a predetermined temperature at which the snap motion of the heat-responsive plate occurs, and also melts easily. A thermo-responsive switch, characterized in that it is provided with a mechanism for separating a fixed contact from a conductive pin to electrically open the circuit when the fixing force of a material is reduced. 2. A mechanism for separating a fixed contact fixed to a conductive pin from the conductive pin when the fixing force of the easily meltable material is reduced, and having a structure in which a restoring force by a spring via an electric insulator is stored. The thermoresponsive switch according to claim 1. 3. A mechanism for separating a fixed contact fixed to a conductive pin from the conductive pin when the fixing force of the easily meltable material is reduced is configured to have a restoring force by a spring made of an electrically insulating material. The heat-actuated switch according to claim 1. 4. The mechanism for separating the fixed contact fixed to the conductive pin from the conductive pin when the fixing force of the easily meltable material is reduced is constituted by a shape memory alloy via an electric insulator. Thermally actuated switch described in.