JP3366979B2 - Circuit protection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit protection device, and more particularly to a motor protector with a compensation function.

[0002]

2. Description of the Related Art Conventionally, in a small hermetic refrigeration compressor (compressor) used for a refrigerator, an air conditioner, etc., FIG.
The protector 2 of the motor 1 schematically illustrated in FIG.

The motor protector 2 is designed to cut off the circuit when an abnormality occurs and prevent the motor from being burned by being incorporated in a circuit for supplying the power supply voltage 3 to the winding of the motor 1.

13 to 18 show an example of the protector 2 called a 3/4 inch type or a dome mount type. In this protector, a nut 6 is arranged at the end of a rod-shaped screw 5 screwed into the center of a case 4 which is a resin molded product, and a snap type bimetal disc 8 is provided between a seat portion 5b of this rod-shaped screw and a washer 7. When mounted, the pair of movable contacts 9 and 10 of the disk 8 are detachably (that is, can be turned on and off) thermally deformed with respect to the fixed terminals (fixed contacts) 11 and 12 embedded in the case 4. It is composed.

The bimetal disk 8 is attached to the screw 5 by caulking the head 5a of the screw 5 at the center thereof, but in a normal state, the movable contacts 9 and 10-fixed as shown in FIG. The contacts 11 and 12 are in contact with each other to connect the circuit of FIG. 12 described above to supply a voltage to the motor 1.

A nickel-chromium resistance wire 13 is connected to the fixed terminal 11, for example, as shown in FIG. The fixed terminal 14 is connected to the motor side, and the fixed terminal 12 is connected to the power source side. In the state of FIG. 13, a current flows between the terminals 14 and 12, and the circuit of FIG. 12 is closed (operating state). Becomes

However, when an overcurrent is about to flow through the motor, the resistance wire 13 self-heats as a heater, and the heat of the compressor itself is added to the bimetal disk 8 when the temperature reaches a preset temperature. As shown in Fig. 14, it is thermally deformed upward. As a result, the above circuit is cut off and the motor is prevented from being burnt out. Further, the bimetal disk 8 is restored to its original shape by cooling after the circuit is cut off, and the circuit is closed and operated.

Although there is a protector of the type in which the heater 13 described above is not provided, an example thereof is shown in FIGS. In this case, the terminal 11 is directly connected to the motor side.

The inventor of the present invention has made various studies on the protector 2 shown above.
It has been found that as the number of operations for repeating the state of Fig. 14 and the state of Fig. 14 increases, the bimetal may crack due to metal fatigue, which may prevent the above-mentioned contact from opening (to the state of Fig. 14). . That is, the contacts are welded to each other. This welding may also occur due to abnormal overcurrent.

As a result, even in an abnormal condition (that is, in general,
Since the circuit cannot be opened when the protector has an operating life, that is, when the metal fatigue described above occurs, the motor burns out.
Burnt lubricating oil, winding coating, solvent, etc. may spout out around it.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a protection device capable of satisfactorily shutting off a circuit and effectively preventing burnout or the like with a simple structure.

[0012]

SUMMARY OF THE INVENTION Namely, the present invention includes first and second fixed contact fixed to the main body, is provided at one end of the thermal deformation member, first in contact with the first fixed contact 1 movable contact and a second movable contact that is provided at the other end of the heat deformable member and is in contact with the second fixed contact, and is provided near one end of the heat deformable member, A first member for preventing the thermal deformation member from returning to maintain the non-contact state when the thermal deformation member is deformed to bring the first fixed contact and the first movable contact into the non-contact state. No. 1 locking member and the other end of the heat deformable member are provided in the vicinity of the other end, and the heat deformable member is deformed to cause the second fixed contact and the second
Second contact for preventing the thermal deformation member from returning to the non-contact state when the non-contact state with the movable contact of
And the first and second locking members,
One end and the other end of the heat-deformable member respectively have a predetermined moving distance.
When it is deformed only by the distance
Has a locking part to prevent the thermal deformation member from returning.
And, said first and second variable by the deformation of the thermal deformation member
When the moving contacts are both in the non-contact state, the thermal deformation member is not prevented from returning, and when only one of the first and second movable contacts is in the non-contact state due to the deformation of the thermal deformation member. Relates to a circuit protection device characterized in that the locking portion prevents the thermal deformation member from returning.

[0013]

[0014]

EXAMPLES Examples of the present invention will be described below.

1 to 6 show a first embodiment in which the present invention is applied to a motor protector. In the protector 22 according to this example, parts common to those of the conventional example shown in FIGS. 13 to 16 described above are denoted by common reference numerals and description thereof may be omitted, but as an important configuration, the fixed terminal ( contact)
Elastically deformable metal pieces on the 11 and 12 sides
20 and 21 are provided for locking the bimetal disk 8.

The metal pieces 20 and 21 have upper portions 20a and 21a.
Is exposed to the inside of the case 4 and is elastically biased so as to always contact the end of the bimetal disk 8. Further, the lower portions 20b and 21b thereof are embedded or fixed in the insulating case 4 by inserting or adhering.

A protector provided with such metal pieces 20 and 21
The operation of 22 will be described. In the state of FIG. 1, the protector 22 is fixed to the compressor case (shell) 23 shown by phantom lines, and the contacts 9-11 and 10-12 contact each other to operate the motor. It shows a normal state.

When an overcurrent flows in the motor as described above, the bimetal disk 8 is thermally deformed upward as shown in FIG. 3, separating the contacts and disconnecting the motor circuit. At this time, regarding the deformation amount of the bimetal disc,
The moving distance of the movable contacts 9 and 10 is the metal piece 2 as shown.
The upper end positions of 0 and 21 are not exceeded.

Therefore, when the bimetal disk 8 returns to the original position next time, the metal pieces 20 and 21 do not hinder the returning operation (there is no problem even during the above-mentioned thermal deformation operation).

However, as shown in FIG. 2, when the welding occurs without separating the contacts 9-11 on the left side due to some cause (abnormal current, crack generation, etc.), and when the metal piece 21 is not provided, the right side will eventually come out. The contacts 10-12 may also be welded together and the circuit may not be interrupted.

As a result of various studies by the present inventor, the above-mentioned welding between both contacts does not occur at the same time, and the operation of the bimetal on the unwelded side is more than that when both contacts are operating. Also found that the distance traveled increased.

That is, as compared with the moving distance l'in the normal operation shown in FIG. 3, the moving distance l of the other contact in the one-side welding is shown in FIG.
It turned out to be big like. This is because when welding on one side, the movement distance is biased to the other side.
For example, it was confirmed that if l '= 1.5 mm, then l = 2.0 mm.

Therefore, the metal piece 21 (further 20), specifically, the tip of the metal piece 21 is arranged within the range of the moving distances 1'to 1 . As a result, when one-side welding occurs as in the state of FIG. 2, when the other contact portion is thermally deformed while resisting the elastic force of the metal piece 21, the moving distance thereof
Since the tip of the metal piece 21 exists within the range of 1 ′ to 1, when the deformation 5 tries to return to the original position,
As described above, the tip of the metal piece 21 enters under the edge of the bimetal disk 8 and elastically bites there.
Therefore, the portion of the contact 10 cannot return to the original position, and remains locked in the position of FIG. 2 by the metal piece 21. The metal piece 21 acts, so to speak, as a “latch” for the bimetal disk 8.

In this way, the motor protector with the compensation function according to the present embodiment can cut off the motor circuit satisfactorily and reliably and effectively prevent the motor from burning. Since the above-mentioned state is still maintained after cooling the bimetal, it is very advantageous that it is highly reliable and can be realized by the metal piece 21 with a simple structure. At the time of the above welding, the protector 22 has already undergone a great change in its characteristics and has reached the end of its service life. Therefore, the motor circuit is disconnected (opened) as described above.
By doing so, it becomes possible to replace the protector while protecting the motor.

On the side of the metal piece 20 as well, when the contact points 10-12 are welded by the same operation as described above, the portion of the contact 9 which has been thermally deformed is locked by the metal piece 20 to interrupt the circuit. You can

The metal piece 21 (further 20) has a spring property as well as a material and size, and in addition to being constantly in light contact with the bimetal, when the bimetal is deformed beyond its tip, it is quickly It needs to be designed to go under the bimetal. It is also necessary that the bimetal should not bend or buckle under pressure from above. Furthermore, it is desirable that the surface of the metal piece should not be worn during repeated opening and closing operations of the bimetal and that wear resistance should be imparted by surface treatment or heat treatment.

As an example, the metal piece 21 (further 20) is made of steel and has a size of 0.1 mm × 3 mm × 11 mm, and the surface treatment can be plated with chromium.

FIG. 6 shows the state at the time of the above-mentioned locking. When the interval between the seat portion 5b of the rod-shaped screw 5 and the washer 7 at the crimping portion for fixing the bimetal disk 8 is t (FIG. It was confirmed that the following relationship exists between t and l.

[0029]

According to this result, l is all larger than l ', l does not change substantially even if t changes, and l slightly changes even at the bimetal temperature, but changes depending on the type of bimetal. It turns out that is large.

In the above, the bimetal is reversed (snap operation) when it is thermally deformed.
The value of is actually a little larger than the above value. However, until the state immediately after that (corresponding to the state of FIG. 2) is a very short time and the measurement cannot follow, the comparison is made in the same state = stable state, and 1 is determined.

FIG. 7 shows a metal piece in the example of FIGS.
It shows an example in consideration of electrical insulation of 21 (20 is also the same).

That is, although the same may be applied to the above-mentioned example, as illustrated in FIG. 7, the contact 10 is made of Cu10a with Ag10b deposited on the surface thereof, and the contact 12 is provided with the Ag coating 12
It is made up of an integrated Cu 12b and stainless steel 12c. Then, at the moment when the contacts 10-12 are about to separate from each other (when the bimetal is thermally deformed), an arc discharge occurs between the contacts 10-12, and the Ag plating 10b, 12a on the surface of each contact.
May peel off and scatter, and this may adhere to the surface of the case 4 as shown by 30 in FIG.

In this case, for example, when the case 4 is flat around the upper portion 21a of the metal piece 21 as shown in FIG. 1, the above-mentioned Ag30 uniformly adheres to the flat surface and contacts the metal piece 21. It may happen. As a result, even if the contacts 10-12 are separated from each other, the metal piece 21 and the Ag 30 are separated between the contacts 10 and 12.
Will be conducted through. With this, the motor circuit cannot be cut off.

Therefore, according to this example, the upper portion 21 of the metal piece 21 is
Since the concave notch 31 is formed in the case 4 around a, the Ag scattered by the above-mentioned arc discharge does not adhere to the side surface of the notch 31. Therefore, the metal piece 21 and the contact point
12 means that case 4 is insulating (for example, made of phenol resin)
Therefore, there is no conduction, and the motor circuit can be reliably cut off. In addition, such a structure and effect are the same also in the other metal piece 20.

Next, as in the above-mentioned example, the fixed contact 12 or
In addition to the case where the movable contact is welded to 11, the present invention is applied when the movable contact portion of the bimetal disk 8 has a crack (due to metal fatigue) on the fixed contact 11 and / or 12 side. It is possible.

That is, when the bimetal disk 8 which is the movable contact portion cracks on at least one of the fixed contact sides (no welding occurs), the opening / closing operation distance of at least one of the fixed contact sides ( The above 1) may temporarily become larger than the normal time (1 ′ above). Therefore, similar to the above-mentioned example, the operating distances 1 ′ to 1
By arranging the tips of the metal pieces 20 and 21 within the range, when the movable contact is thermally deformed on the above side, the metal piece elastically bites below the bimetal disk immediately after the deformation. It is possible to prevent the return operation of.

At this time, the protector is already in a state in which it can be said that the characteristics have largely changed and the regular life has ended, so there is no problem even if the motor circuit is opened at this point, and the present invention The purpose of can be realized.

FIG. 8 shows an example in which the pressure applied from the metal piece 21 (and also 20) to the bimetal disk 8 is reduced.

That is, by bending the upper part of the metal piece 21 (and also 20) toward the bimetal disk 8 side, when the contact points 10-12 are in contact, the metal piece 21 with respect to the bimetal disk 8 is made. (Specifically, the upper portion 21a) does not come into contact with each other and can be configured so as not to affect the "open" characteristic (thermal deformation operation) of the disk.

Therefore, the bimetal disk 8 receives a minimum external force from the metal piece 21 during its operation, and the original characteristics of the motor protector are not impaired.

In the normal thermal deformation state, the metal piece 21 contacts the disk 8 as indicated by the alternate long and short dash line, but this does not hinder the operation of the disk.

In this example, instead of bending the metal piece 21 as shown in FIG. 8, the tip portion may be slightly bent or bent as shown by a chain double-dashed line. In this case,
This is advantageous because it is possible to reduce the contact of the metal piece 21 with the disk 8 during operation.

In any case, by disposing the upper end of the metal piece 21 within the operating range 1 of the disk at the time of one-side welding described above, the disk 8 resists the elastic force of the metal piece 21 during the operation. When moved, the metal piece 21 enters the lower side of the disk 8 at the position of the operation range l and locks the metal piece 21 to prevent the return operation.

FIG. 9 shows another embodiment of the present invention, which is different from the above-mentioned embodiment in that the metal pieces 20 and 21 are bent inwardly in a linear shape as shown in the drawing. Is.

That is, the bimetal disk 8 may crack before the above-mentioned welding, and at this time, the characteristics as a protector are largely lost. At this time, however, the force (elastic deformation or restoration) when the bimetal is opened and closed. Power of time) is weakening. Therefore, as the shape of the bent portions of the metal pieces 20 and 21, the bent portions 20c and 21c are formed at a gentle angle with respect to the movement of the bimetal in the opening direction, and relatively sharp with respect to the movement of the bimetal in the closing direction. The bent portions 20d and 21d have different angles.

Therefore, the deformation of the bimetal disc 8 in the opening direction does not cause any trouble because it easily slides on the bent portions 20c and 21c, but when the return from the open state to the closed state occurs, the angle is steep. The bent portions 20d and 21d prevent the return and are locked there. This can be sufficiently realized because the restoring force of the cracked disk 8 is weak.

10 and 11 show still another embodiment of the present invention. In the example of FIG. 10, the opening 40 of the case 4
Insert the metal pieces 20 and 21 for locking having the shape as shown in the figure from the side, and fix the vertical portions 20e and 21e to the wall surface of the case 4 by adhesion, and the upper side of the bent portions 20f and 21f to the upper side. Department
20g and 21g are connected in series.

These hypotenuse parts 20g and 21g have the same function as the curved part shown by the chain double-dashed line in FIG. However, in all the examples described above, the metal piece is inserted into the insertion hole provided in the case 4 (and is inserted from the bottom surface of the case 4 or the side to which the terminal is soldered). In case 4 is the top surface or opening
Since it is inserted from the 40 side, there is an advantage that it is easy to install the metal piece.

In the example of FIG. 11, basically, similar to FIG. 10, the metal pieces 20 and 21 are inserted and fixed from the side of the opening 40 of the case 4, but the metal pieces 20 and 21 have a flat plate shape. The bent portions 20h and 21h formed by punching out a part are integrally provided. Therefore, the same operation as in the example of FIG. 10 is performed, and at the same time, the production is facilitated in that the bent portion is formed on the metal piece by punching.

Although the heater 13 and the terminal 14 described above are not shown in FIGS. 9 to 11, they may be provided in the same manner as in the above-described example, or the heater shown in FIGS. 17 to 18 is not provided. It may have a structure (however, in this case, the terminal 14 itself may be omitted). This may be the same for the examples of FIGS.

Although the present invention has been described with reference to the embodiments, the above-described embodiments can be further modified based on the technical idea of the present invention.

For example, the shape and mounting method of the metal piece as the above-mentioned locking means may be variously changed, and it may be rod-shaped or the like other than plate-shaped. Further, it does not necessarily have to be made of metal, and can be formed of a non-metal or an insulating material or a metal coated with an insulating material, for example, a hard plastic having heat resistance and arc resistance.

Although the above-mentioned locking means is manufactured separately from the case and attached to the case, it may be insert-molded when the case is molded, or in the case of plastic, a portion corresponding to a metal piece may be formed. For example, a phenol resin may be integrally formed with the case.

Further, each part of the protector can be variously changed, for example, the number of movable and fixed contacts may be changed according to the situation. Although the above description has been made mainly for the protector with a heater, the present invention can be applied to a protector without a heater as shown in FIGS.

Further, the present invention can be widely applied or applied not only as the above-mentioned motor protector but also as a protector for various circuits.

[0057]

As described above, according to the present invention, when the movable contact portion is fixed or cracked at any of the fixed contact portions, the movable contact portion is within the range where the movable contact portion undergoes the thermal deformation operation. Since the locking means for preventing recovery is provided, the movable contact portion and the fixed contact portion can be brought into a non-contact state during an abnormality, and the circuit can be reliably cut off.

Further, since no special structure or material is required for breaking the circuit and the above-mentioned locking means may be provided,
Circuit break can be realized with a simple structure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view (a cross-sectional view taken along the line I-I of FIG. 4) of a motor protector according to a first embodiment of the present invention at a normal time.

FIG. 2 is a cross-sectional view of the protector when an abnormality occurs.

FIG. 3 is a sectional view of the protector during normal operation.

FIG. 4 is a plan view of the protector.

FIG. 5 is a plan view of the protector excluding a bimetal disc.

FIG. 6 is a cross-sectional view for explaining the operation of the protector.

FIG. 7 is a cross-sectional view of essential parts of a motor protector according to another embodiment of the present invention.

FIG. 8 is a cross-sectional view of essential parts of a motor protector according to another embodiment of the present invention.

FIG. 9 is a sectional view of a motor protector according to another embodiment of the present invention.

FIG. 10 is a sectional view of a motor protector according to another embodiment of the present invention.

FIG. 11 is a cross-sectional view of a motor protector according to another embodiment of the present invention.

FIG. 12 is a schematic diagram of a conventional motor circuit.

FIG. 13 is a cross-sectional view (cross-sectional view taken along the line XIII-XIII in FIG. 15) of the conventional motor protector during normal operation.

FIG. 14 is a sectional view of the motor protector during normal operation.

FIG. 15 is a plan view of the motor protector without a bimetal disc.

FIG. 16 is a schematic circuit diagram of the motor protector.

FIG. 17 is a plan view of a conventional motor protector without a heater.

FIG. 18 is a schematic circuit diagram of the motor protector.

[Explanation of symbols]

5 screws 6 nuts 7 washers 8 bimetal discs 9, 10 movable contacts 11, 12 fixed contact (terminal) 13 heater 14 terminals 20, 21 Metal piece (locking means) 22 Motor protector l Moving distance in case of abnormality l'movement distance under normal conditions

Claims (3)

(57) [Claims] 1. A first and second fixed contact fixed to the main body, and a first movable contact provided at one end of the heat deformable member and in contact with the first fixed contact, A second movable contact that is provided at the other end of the heat deformable member and is in contact with the second fixed contact, and is provided near one end of the heat deformable member, and the heat deformable member is deformed. And a first locking member for preventing the thermal deformation member from returning and holding the non-contact state when the first fixed contact and the first movable contact are in the non-contact state. The thermal deformation member is provided in the vicinity of the other end of the thermal deformation member, and when the thermal deformation member is deformed to bring the second fixed contact and the second movable contact into a non-contact state, A second locking member for preventing the return and holding the non-contact state, The second locking member, the heat
One end and the other end of the deformable member each have a predetermined movement distance
When it is deformed, it enters the lower part of the thermal deformation member and
Has a locking portion for preventing the return of the thermal deformation member, the restoration of the thermal deformation member when the first and second movable contact by the deformation of the thermal deformation member are both a non-contact state not prevent, before when only one of said first or second movable contact is in a non-contact state by the deformation of the thermal deformation member
A circuit protection device, characterized in that the locking portion prevents the thermal deformation member from returning. 2. The first and second locking members are metal pieces extending in the deformation direction of the heat deformable member, and when the heat deformable member is deformed higher than the height of the locking portion of the metal piece. The circuit protection device according to claim 1, wherein the locking portion of the metal piece is inserted into a lower portion of the heat deformable member to prevent the heat deformable member from returning. 3. The circuit protection device according to claim 1, wherein the heat-deformable member is a bimetal disc fixed to the main body at a central portion thereof.