JPH07176249A - Overload protector device - Google Patents

Abstract

PURPOSE:To maintain high reliability at the time of ordinary use by fixing a part where an adjusting screw penetrates a bottom surface of a bottomed cylindrical case and a part where a spring is compressed, with a thermally fusible material of melting point higher than an acting temperature of a bimetal, so as to quickly interrupt an electric line at the prescribed acting temperature. CONSTITUTION:When an overload current flows in a load, a bimetal 5 is heated by a heater wire 12, and when the bimetal 5 reaches a prescribed temperature, at the time of automatic resetting action, the bimetal 5 flips to quickly open movable contacts 3, 4 from fixed contacts 7, 8, and to break a circuit. When repeated opening/closing the bimetal 5 to generate, by any possibility, an abnormal high temperature by fusing the movable contacts 3, 4, a thermal fusible metal 19 for fixing a head part 6a of an adjusting screw 6 is melted. Simultaneously with melting a thermal fusible material of fixing a spring 20, and pressing force is increased. As a result, in a final trouble mode, the head part 6a of the screw 6 and the bimetal 5 are pressed up to break the circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload protection device equipped with a bimetal suitable for use in an electric motor or the like, and more particularly to an overload protection device capable of passing a large current without causing contact welding.

[0002]

2. Description of the Related Art Generally, products using electric motors such as refrigerators, air conditioners, and dehumidifiers are provided with an overload protection device in order to prevent overheating and burning of the electric motors. And
Various overload protection devices of this type have hitherto been proposed.

The prior art relating to the overload protection device will be described below step by step with reference to FIGS. First, the overload protection device described in Japanese Utility Model Laid-Open No. 59-72641 will be described with reference to FIGS. 12 to 14.

FIG. 12 is a vertical sectional view showing an overload protection device disclosed in Japanese Utility Model Laid-Open No. 59-72641, and FIG. 13 is a plan view taken along the line B--B in FIG.

In FIG. 12, the case 1 is made of a heat-resistant insulating material such as phenol resin or unsaturated polyester resin and has a bottomed cylindrical shape. The case 1 is covered with a lid 2 to form an internal space.

An adjusting screw 6 made of brass is installed in the inner space at the center of the bottom of the case 1 so as to penetrate from the inner bottom surface 1b to the outer bottom surface 1a. A head 6a is provided at the end of the. The disc-shaped bimetal 5 is attached to the adjusting screw 6 by inserting the adjusting screw 6 into the support hole 5a, and the inside of the case 1 with the bimetal 5 by the adjusting screw 6 is attached. A spring 13 is attached between the spring 13 and the bottom surface 1b. The spring 13 is in a compressed state, and the bimetal 5 is pressed against the head portion 6a of the adjusting screw 6 by its urging force.

Movable contacts 3 and 4 are fixed to each other on the outer peripheral portion of the surface (lower surface) of the bimetal 5 facing the inner bottom surface 1b by resistance welding so as to face each other. Further, a fixed terminal 9 is fixed so as to penetrate from the inner bottom surface 1b of the case 1 to the outer bottom surface 1a, and the fixed contact 9 is provided at the tip of the fixed terminal 9 so as to face the movable contact 3 of the bimetal 5. Is stuck.

Similarly, the tip of the fixed terminal 10 which penetrates from the inner bottom surface 1b of the case 1 to the outer bottom surface 1a and is fixed is made to face the movable contact 4 of the bimetal 5,
The fixed contact 8 is fixed.

Further, the heater terminal 11 is fixed so as to penetrate from the inner bottom surface 1b of the case 1 to the outer bottom surface 1a, and between the end of the heater terminal 11 and the tip of the fixed terminal 9 in the inner space of the case 1. The heater wire 12 is connected by welding or the like. The fixed terminal 10 and the heater terminal 11 are external terminals of the overload protection device 14 '. The heater wire 12 is close to the lower surface of the bimetal 5, and
As shown in FIG. 12, the bimetal 5 is arranged so as to wrap around the side toward the adjusting screw 6 in FIG. 12, and the bimetal 5 is heated over the entire circumference by the heat generation of the heater wire 12.

The bimetal 5 has a curved shape centered on the central portion, and when the temperature is low, the central portion has a curved shape protruding toward the lid 2 side as shown in the drawing, and the movable contacts 3, 4 are provided. Are in contact with the fixed contacts 7 and 8, respectively. As a result, an electric path from the fixed terminal 10 to the heater terminal 11 through the fixed contact 8, the movable contact 4, the bimetal 5, the movable contact 3, the fixed contact 7, the fixed terminal 9, and the heater wire 12 is formed.

The operation of this bimetal and the terms used in this specification will be described below. When the temperature of the bimetal 5 rises and reaches a certain temperature, the bimetal 5
Contrary to the orientation shown in FIG. 12, the central portion is the inner bottom surface 1
The shape suddenly changes to a curved shape protruding toward the b side. This is referred to as "reversal motion" below, and bimetal 5 by reversal motion
The state of is called "inversion state". Further, the temperature of the bimetal 5 in which this reversal motion occurs is referred to as "reversal operation temperature". When the bimetal 5 moves in reverse, the movable contacts 3 and 4 separate from the fixed contacts 7 and 8, respectively, and the electric path is cut off.

When the temperature of the bimetal 5 in the inverted state drops to a certain temperature, the bimetal 5 returns to the direction shown in FIG. Hereinafter, this is called "return movement", and the illustrated state by this return movement is called "original state". Further, the temperature of the bimetal 5 in which the return movement occurs is referred to as "return operation temperature". When the bimetal 5 returns from the inverted state to the original state, the movable contacts 3 and 4 are fixed contacts 7 and 8 respectively.
And the electric path is formed again.

Next, the operation when the overload protection device 14 'is used in an electric motor will be specifically described with reference to FIG. FIG. 14 is a circuit diagram showing an electrical connection relationship when an overload protection device 14 ', which is an overload protection device having a heater, is used for an electric motor.

In FIG. 14, the overload protection device 14 'is shown only for the above-mentioned electric circuit components, and the electric motor 15 is shown only for the windings. In the electric motor 15, the starting winding 17
And a starting device 16 are connected in parallel to the main winding 18. The electric motor 15 and the overload protection device 14 ′ are connected in series by connecting one terminal of the electric motor 15 to the heater terminal 11 of the overload protection device 14 ′. As a result, from the fixed terminal 10 of the overload protection device 14 'to the bimetal 5, the heater wire 12, the heater terminal 11
A current flows through the starting winding 17 and the main winding 18 of the electric motor 15 via the.

When the mechanical lock of the electric motor 15 is generated during the operation of the electric motor 15 due to seizure of the bearing portion of the electric motor 15 or a compressor not shown in the figure, or intrusion of dust into the rotating portion, That low
Since the rotor does not rotate, a large current corresponding to the starting current flows and continues to flow as long as the rotor is locked with the power supply connected. This is called "restraint current" and is about 4 to 5 times the rated current of the electric motor 15. Normally, the time (starting time) during which the starting current flows at the time of normal starting is as short as 2 to 3 seconds, so the electric motor 15 is designed to sufficiently withstand such a large starting current that flows in a short time. . However, it is not preferable that the constraint current continues to flow in the electric motor 15 and its current circuit for a long time because it is not taken into consideration in the design.

The overload protection device 14 'is intended to solve this problem, and a large binding current continues to flow in the motor 15 to increase self-heating of the bimetal 5 and the heater wire 12, and the temperature of the bimetal 5 reverses. When the temperature is reached, the bimetal 5 makes a sudden reversal motion at that moment, and the movable contacts 3 and 4 separate from the fixed contacts 7 and 8 as described above to stop the electric motor 15. When there is a power interruption like this,
The bimetal 5 and the heater wire 12 start cooling, and when the temperature of the bimetal 5 reaches the return operation temperature, the bimetal 5 rapidly returns to its original state, and the movable contacts 3, 4
Contact the fixed contacts 7 and 8, respectively, and the energization of the electric motor 15 is restarted. At this time, if the restraint state of the electric motor 15 is released, the bimetal 5 does not perform the reversing motion again, and the electric motor 15 operates normally.

Next, the overload protection device described in Japanese Utility Model Laid-Open No. 60-183349 will be described with reference to FIGS.
Will be explained. FIG. 15 is a schematic view of Shokai 60-18334.
It is a longitudinal cross-sectional view which shows the overload protection apparatus of the 9th publication. FIG. 16 is a circuit diagram showing an electrical connection relationship when an overload protection device 14 ″, which is an overload protection device without a heater, is used for an electric motor. FIG. 17 is a top view of the bimetal 5 partially broken.

As shown in FIG. 15, this overload protection device 14 ″ is basically different from the overload protection device 14 ′ shown in FIG. 12 in that a heater wire is not provided. For this reason, the fixed contact 9 having the fixed contact 7 at its tip penetrates the bottom of the case 1 and is projected to the outside, and the fixed terminal 10
Also serves as an external terminal. When the movable contacts 3 and 4 are in contact with the fixed contacts 7 and 8, respectively, the fixed terminal 1
An electric path from 0 to the fixed terminal 9 via the fixed contact 8, the movable contact 4, the bimetal 5, the movable contact 3, and the fixed contact 7 is formed.

The overload protection device 14 ″ is installed in the electric motor 1
When used for No. 5, as shown in FIG. 16, one fixed terminal 9 of the overload protection device 14 ″ is connected to one terminal of the electric motor 15.

When some abnormality occurs in the electric motor 15 and a large restricted current flows, the self-heating of the bimetal 5 increases, and when the temperature reaches the reversing operation temperature, the bimetal 5 suddenly makes a reversing motion at this moment. , The movable contacts 3 and 4 are separated from the fixed contacts 7 and 8, respectively, and the energization of the electric motor 15 is stopped. When the energization is stopped in this way, the bimetal 5 begins to cool, and when the temperature of the bimetal 5 reaches the return operation temperature, the bimetal 5 rapidly reverses and returns to the original state, and the movable contacts 3, 4 Are connected to the fixed contacts 7 and 8, respectively, and the energization of the electric motor 15 is restarted.

At this time, if the restraint state of the electric motor 15 is not released, the bimetal 5 does not perform the reversing motion again, and the electric motor 15 operates normally. As described above, according to the above-mentioned conventional examples, if the restrained state is released while the bimetal 5 is in the inverted state, the electric motor 15 is in a normal operating state and overheat burnout can be prevented.

However, when the abnormal state of the electric motor 15 is not eliminated, even if the bimetal 5 returns to the original state and returns to the original state, the electric motor 15 is restrained again, so that the overload protection device 14 '' is largely restrained. Current flows,
The bimetal 5 is inverted again to be in the inverted state, and the motor 15
Energization stops. Therefore, when the abnormal state of the electric motor 15 is not eliminated, the bimetal 5 repeats the reversing motion and the returning motion, and when the number of repetitions increases, the bimetal 5 eventually fatigues and breaks.

The overload protection device 14 'shown in FIG. 12 and the overload protection device 14''shown in FIG.
As shown in FIG. 7, a bimetal 5 having radial slits 5b to 5g provided in a support hole 5a into which an adjusting screw 6 is fitted is used. When the bimetal 5 repeats the reversing motion and the returning motion as described above. For example, a break E occurs from the tip 5b 'of the slit 5b.

Further, in the overload protection device for switching a large current, since the large movable contacts 3 and 4 commensurate with the current are used, the degree of freedom during the reversing operation of the bimetal 5 at the joint of the movable contacts 3 and 4 is increased. However, since the stress in this portion increases, the fracture may proceed from the periphery of the movable contacts 3 and 4 at the same time.

When the bimetal 5 breaks in this way, the characteristics of the bimetal 5 change, leading to a decrease in contact pressure and a decrease in contact opening force, as well as a change in reversing operation temperature and a returning operation temperature, which results in reversing operation. Also, the reversing operation amount of the movable contacts 3 and 4 is reduced, and the reversing operation interval is shortened, and the energization rate of the restricted current flowing through the bimetal 5 and the heater wire 12 is increased. The temperature rises. Also,
The final failure state caused by the repetitive movement of the reversing movement and the returning movement is the contact welding of the movable contacts 3 and 4 and the fixed contacts 7 and 8.

When the contact welding occurs in this way, a large binding current continuously flows through the winding of the electric motor 15 and the bimetal 5 of the overload protection devices 14 ', 14 ", and the winding of the electric motor 15 is continuously wound. When the internal temperature of the case 1 rises due to the heat generation of the bimetal 5 and the heater wire 12 and rises above the heat resistant temperature of the case 1 and the lid 2, the case 1 and the lid 2 are heated. The surroundings of the bimetal 5, etc. will be burned out.

In the conventional example shown in FIG. 12, if the internal temperature of the case 1 rises abnormally and the heater wire 12 is broken, the electric circuit of the overload protection device 14 'is cut off to prevent the above burnout. However, the heater wire 12 does not always shut off, which is a safety issue. Further, even in the case of the overload protection device 14 ″ having no heater wire shown in FIG. 15, even this effect cannot be expected.

Overload protection device 1 normally used in refrigerators
The fusing current of the bimetals 4 ′ and 14 ″ is 70 A or more after 5 seconds of energization. Moreover, it is 100 A or more in the one used for an air conditioner or the like. This indicates that the fuse will not blow unless at least twice the maximum restricted current of the electric motor 15 used for them flows.

Various proposals have hitherto been made as methods for solving the above problems. As an example thereof, in the overload protection device described in Japanese Utility Model Laid-Open No. 59-72641, a heat resistant material such as ceramic is used for the case.

Further, in the overload protection device disclosed in Japanese Utility Model Laid-Open No. 63-174145, a motion counter having a plurality of saw-tooth projections is provided, and the saw-tooth projections are sequentially changed each time the bimetal returns. When engaged, the motion count drops, and when the bimetal reverses a number of times equal to the number of serrated protrusions, the motion counter contacts the inner bottom surface of the case to prevent the bimetal from making a return motion.
According to this, when the reversal operation of the bimetal continues, the bimetal performs the returning motion for a predetermined number of times, and it is considered that the circuit is in a dangerous state.

Further, in the overload protection device disclosed in Japanese Patent Laid-Open No. 63-224125, a first bimetal and a second bimetal having a reversal temperature higher than that of the first bimetal are electrically connected in series. , The first bimetal is made to perform the reversing operation due to the generation of the abnormal current, the first bimetal repeats the reversing operation and the returning operation without the abnormal state being eliminated, and finally the first bimetal is broken and the contact welding is performed. In the event of occurrence of abnormal temperature, the abnormal temperature rise resulting from this causes the second bimetal to reverse and interrupt the abnormal current.

Further, in the overload protection device disclosed in Japanese Utility Model Laid-Open No. 64-1450, the second bimetal is brought into contact with the lower surface of the first bimetal, and the first bimetal breaks to cause contact welding. When it occurs, the second bimetal makes an inversion movement to lift the first bimetal.

Further, in the overload protection device disclosed in Japanese Utility Model Laid-Open No. 64-35642, the adjusting screw is composed of a head for attaching the bimetal and a screw portion other than the head, and each of them is a heat-soluble metal. It has been fixed. Here, the head portion is provided with a recessed portion, and the head portion is fixed to the screw portion by filling the melted material of the heat-soluble metal and inserting the end portion of the screw portion. By the way, normally, the bimetal is pressed against this head by the spring attached to the adjusting screw. However, when the temperature of the bimetal becomes high due to the contact welding of the bimetal, the heat-fusible metal melts and the head and the adjusting screw are fixed. When released, the biasing force of the spring lifts the bimetal and the head.

Further, in the overload protection device disclosed in Japanese Patent Laid-Open No. 1-320723, a fusible body is interposed between the adjusting screw and the head bimetal, and the bimetal is usually attached to the fusible body by a spring attached to the adjusting screw. Although being pressed, when the bimetal is welded to the contact and the temperature inside the case rises, the fusible body melts and the biasing force of the spring moves the bimetal to the head and lifts it.

Further, in the overload protection device described in Japanese Patent Laid-Open No. 2-444529, the adjusting screw is divided into a head portion and a body portion, and a head boss made of a shape memory alloy is press-fitted into a hole of the body portion. The bimetal is attached by fitting and fixing. Normally, the bimetal is pressed against the head by the spring attached to the adjusting screw, but when the bimetal contacts weld and the temperature inside the case rises, the boss of the head contracts and separates from the body part, and the biasing force of the spring is applied. Lifts the bimetal and head.

Further, in the overload protection device disclosed in Japanese Utility Model Laid-Open No. 128328/1990, a locking metal fitting is locked to the body portion of the adjusting screw on the head side, and normally the bimetal is provided by a spring attached to the adjusting screw. It is pressed by the locking metal fitting. Then, when the contact of the bimetal is welded and the temperature inside the case rises, the locking metal piece is separated from the body portion of the adjusting screw, and the bimetal and the locking metal piece are lifted to the head by the biasing force of the spring.

Further, in the overload protection device described in Japanese Utility Model Laid-Open No. 2-128339, a support metal fitting, which is a small dimension, is contacted between the head of the adjusting screw and the bimetal, and the bimetal is supported by a spring. Is pressed against. And
When the bimetal is welded to the contact and the temperature inside the case rises, the size of the support metal fitting becomes small and the bimetal is lifted upward by the biasing force of the spring.

[0038]

As described above, various countermeasures against the contact welding of bimetal have been proposed, but each has the following problems.

That is, if the case is made of ceramic as in the overload protection device described in Japanese Utility Model Laid-Open No. 59-72641, it is possible to avoid burning of the case, but the winding of the motor is inevitable. Is also expensive.

Further, in the prior art in which the motion counter plate is provided as in the overload protection device described in Japanese Utility Model Laid-Open No. 63-174145, the number of repetitive motions of the bimetal reversing motion and the returning motion is increased by this motion counter plate. Is limited,

(1) In the case of an overload protection device used in a refrigerator, an air conditioner, a dehumidifier, etc., the bimetal is reversed by the motion counter plate even if the electric compressor fails, that is, other than mechanical lock. It is easy to be held.

(2) The position of the motion counter plate is moved even in the motion check during the adjustment work, and the number of remaining motions is reduced. There are still issues to be solved when putting into practical use.

Furthermore, when the first and second bimetals connected in series are used as in the overload protection device disclosed in Japanese Utility Model Laid-Open No. 224125/1988, it is necessary to energize them simultaneously. From that,

(1) The ratio of the resistances of the first and second bimetals, that is, the range of the amount of current that can be flown is limited according to the specific resistance of the bimetals.

(2) When the resistance of one of the bimetals is small and the amount of heat generated by itself is small, it is necessary to provide a heater wire, but it is necessary to secure an insulation distance between the bimetal and the heater wire. Therefore, the space occupied by the bimetal and the heater wire also becomes large, and the size of the overload protection device becomes large.

(3) Since it is necessary to provide a contact using an expensive metal such as gold or silver for each of the first and second bimetals, the device itself becomes expensive. There are still issues to be solved when putting into practical use.

Further, when the adjusting screw and its head are fixed with a heat-fusible metal, as in the overload protection device described in Japanese Utility Model Laid-Open No. 64-35642,

(1) When the contact between the bimetal and the temperature rises due to contact welding, the heat-meltable metal begins to melt and the heads of the bimetal and the adjusting screw are lifted by the spring. Is done gently. When the movable contact is disengaged from the fixed contact on the inner bottom surface of the case by lifting the bimetal, the heat source is lost at the same time because the electric path is cut off, and the heat-fusible metal moves toward the solid phase. However, in this way, when the spring force does not act sufficiently to overcome the viscosity of the heat-soluble metal, the contact separation distance (contact gap) between the movable contact and the fixed contact when the bimetal is lifted is sufficient. I can't secure it.

(2) When the heat-fusible metal is solidified as described above, it is difficult for the spring to lift the bimetal. This is expected to become an obstacle especially when obtaining an overload protection device for a large current, which is likely to cause contact welding.

(3) When binding by a heat-soluble metal,
Since it is pushed up by the spring, the temperature rises and the metal strength decreases, so some strain is unavoidable. Therefore, in order for the bimetal to operate normally during normal operation, its melting point must have a sufficient temperature difference (usually the temperature difference at this time is 40 to 50 ° C.) with respect to the reversal operation temperature of the bimetal. . However, even if such a temperature difference is provided, there are problems in guaranteeing the operating characteristics and reliability of the device that the reversal operating temperature of the bimetal is not constant due to the pushing force of the spring. Therefore, there is a problem in practical application such as the fact that the contact welding cannot be released in the opening and closing of a large current load in which the contact welding force becomes large for the above reasons.

Further, in the case where the fusible body is interposed between the head of the adjusting screw and the bimetal, as in the overload protection device described in JP-A-1-320723,

(1) The desirable melting point of the fusible element is determined by the balance between the spring force and the viscosity of the fusible element in order to ensure normal operation of the bimetal during normal operation of the device. Therefore, as described above, the melting point is usually required to have a sufficient temperature difference with respect to the reversal operation temperature of the bimetal. On the other hand, if a spring having an excessive spring force is used in the overload protection device, the reversal operation temperature of the bimetal appears to change. Therefore, it is difficult to use a spring having a large spring force because of the operating characteristics of the bimetal. is there.

(2) Therefore, in a large current load switching region where the contact welding force becomes large, a spring having a certain amount of spring force must be used, so contact welding cannot be released unless the operating characteristic guarantee is sacrificed. The problem remains. There is a problem in practical application.

Further, in the overload protection device described in Japanese Utility Model Laid-Open No. 2-128339, in which a small-sized support metal fitting is interposed between the head of the adjusting screw and the bimetal,

(1) The supporting position of the bimetal is determined by the balance between the bimetal and the elasticity of the spring and the support metal fitting, and there is a design and manufacturing difficulty in controlling the reversal operation temperature of the bimetal. In other words, the reversal return temperature of the bimetal is determined by the balance between the elasticity of the spring and the support metal fittings. It is difficult to balance and stabilize it. Therefore, the spring force of the spring must be designed in consideration of the elasticity of the support metal fitting, and cannot be made too large. Therefore, the range of practical use is naturally limited.

(2) Therefore, when opening and closing a large current load that requires a large spring force, the contact welding force becomes large and it is difficult to use. There is a problem in practical application.

Furthermore, there is no fear of instability of the operating temperature of the bimetal or change of the bimetal supporting position.
529 and Japanese Utility Model Laid-Open No. 2-128338,

(1) When the bimetal is pressed by a spring having an excessive spring force, a part of the bimetal is deformed and the reversal operation temperature and the reversion return temperature change greatly, which limits the practical range.

(2) Generally, the plate thickness of bimetal is 0.15.
~ 0.2 mm for bimetal reversal operating temperature,
The spring load capable of assembling and adjusting the reverse return temperature is 400 g or less. If it exceeds 400 g, not only the yield during assembly and adjustment deteriorates, but also the above-mentioned temperature change during repeated operation becomes large, and the original current and temperature operating characteristics cannot be maintained, which impedes practical application.

(3) As a result, if it is attempted to release the contact welding with a spring load of 400 g or less, the electric motor output used for the 100 V power supply is 350 W, and the electric motor output used for the 200 V power supply is about 750 W. There is a possibility that the expected effect may not be obtained at 100% in a load region exceeding this. The conventional examples disclosed as described above are not suitable for opening and closing the load of the overload protection device in the case of passing a large current in any case, and their use range is limited.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and its purpose is to rapidly and permanently cut off the electric circuit at a predetermined operating temperature, and to have high reliability in normal use. It is an object of the present invention to provide an overload protection device for a large current, which is simple and inexpensive in structure, so that it is possible to maintain the characteristics.

[0061]

In order to achieve the above object, the structure of the first invention relating to the overload protection device of the present invention is a bottomed cylindrical case, a disk-shaped bimetal,
An adjusting screw and a spring are provided, the adjusting screw penetrates a bottom surface of the bottomed cylindrical case, the bottomed cylindrical case includes a pair of fixed contacts, and the disc-shaped bimetal is , A pair of movable contacts fixed to a position facing the fixed contact, and in contact with one end of the spring,
The spring is supported by the adjusting screw, the spring is attached so that the central axis direction of the spring coincides with the adjusting screw direction, and the disc-shaped bimetal is pressed and held in the head direction of the adjusting screw. In an overload protection device configured to move the supporting position of the disc-shaped bimetal by the elastic force of the spring when the operating temperature of the disc-shaped bimetal is higher than that of the spring. Part to full compression or close to it,
In addition, the portion where the adjusting screw penetrates the bottom surface of the bottomed cylindrical case and the portion of the compressed spring that extends over the penetrating portion are heat-fusible having a melting point higher than the operating temperature of the bimetal. The material is fixed.

Further, in order to achieve the above object, the structure of the second invention relating to the overload protection device of the present invention is a bottomed cylindrical case, a disk-shaped bimetal, an adjusting screw,
The adjusting screw has a first spring and a second spring,
Penetrating the bottom surface of the bottomed tubular case, the bottomed tubular case includes a pair of fixed contacts, and the disc-shaped bimetal fixes a pair of movable contacts at a position facing the fixed contacts. And being supported by the adjusting screw in a state of being in contact with one end of the first spring, the first spring is attached so that the central axis direction thereof coincides with the adjusting screw direction, and , The disk-shaped bimetal is pressed and held in the head direction of the adjustment screw, and the second spring is attached so that the central axis direction thereof coincides with the adjustment screw direction. In the overload protection device configured such that the support position of the disc-shaped bimetal moves by the elastic force of the first spring when the temperature becomes higher than the operating temperature of the second spring, , Note: The first spring and the second spring are compressed in the direction in which the spring force acts on the spring so as to be fully compressed or a state close thereto, and the first spring and the second spring are stacked and arranged, and the adjustment screw is The portion penetrating the bottom surface of the bottomed cylindrical case and the compressed second spring extending over the penetrating portion are made of a heat-fusible material having a melting point higher than the operating temperature of the disc-shaped bimetal. It is designed to be fixed.

More specifically, the constitutions of the first and second inventions are such that an alloy containing tin and lead as main components is used as the heat-fusible material.

Further, in detail of another constitution of the first and second inventions, a temperature sensitive agent made of a chemical substance is used for the heat-soluble material.

Further, in order to achieve the above object, the structure of the third invention relating to the overload protection device of the present invention is a case having a bottomed cylindrical shape, a disk-shaped bimetal, an adjusting screw, and a first And a second spring, the adjusting screw penetrates a bottom surface of the bottomed cylindrical case, and the bottomed cylindrical case includes a pair of fixed contacts, and the disk shape. The bimetal has a pair of movable contacts fixed to a position facing the fixed contact, and is supported by the adjustment screw in a state of being in contact with one end of the first spring, and the first spring is It is attached so that the central axis direction and the adjusting screw direction match, and the disc-shaped bimetal is pressed and held in the head direction of the adjusting screw,
The second spring is attached so that the central axis direction thereof and the adjusting screw direction coincide with each other, and when the temperature is higher than the operating temperature of the bimetal, the supporting position of the disc-shaped bimetal is the first spring. In the overload protection device that is configured to move by the elastic force of the second spring, the second spring compresses fully or nearly in the acting direction of the spring force of the first spring, and And arranging the first spring and the second spring in a stack, and the second spring is made of a shape memory alloy having an extension memory temperature higher than an operating temperature of the disc-shaped bimetal. It was done.

More specifically, a non-ferrous or ferrous unidirectional material is used for the shape memory alloy.

More specifically, the non-ferrous shape memory alloy is a Ni--Ti alloy or a Cu alloy, and the ferrous shape memory alloy is a stainless steel or a Cr alloy.

[0068]

When the contact welding occurs at the end of the life of the bimetal performing the snap action operation (repetitive opening / closing operation of the bimetal), a large binding current continuously flows through the bimetal or the bimetal and the heater wire due to the contact welding. At that time, the bimetal or the bimetal and the heater wire generate heat, and the temperature of the internal space of the overload protection device rises.

1. When the temperature rise reaches the temperature at which the heat-fusible body fixing the spring is melted, the liquefied and fixed spring becomes elastic, and the force pressing the bimetal increases accordingly.

Alternatively, since the position where the bimetal is supported can be moved by the temperature rise at that time, both the increased pressing force as well as the inherent bimetal pressing force act as the bimetal lifting force. By this action and effect, the welding of the contacts is eliminated and the bimetal moves upward, so that the circuit is cut off.

2. Further, when the temperature rise reaches the shape memory temperature of the spring made of a shape memory alloy, the shape memory spring restores the stored original shape and acts as a pushing force of the bimetal.

If the supporting portion of the bimetal is in a position to move due to the temperature rise at that time, it acts as a unique bimetal pushing force, and this action effect releases the contact welding and moves the bimetal upward. By doing so, the circuit is cut off. As a result, since the overcurrent does not continue to flow, it is possible to prevent the overload protection device from burning due to the load.

As for the structure of the overload protection device, since the structure of the part other than the spring of the conventional overload protection device is not changed, the above-mentioned operation can be obtained at low cost.

Further, unlike the overload protection device described in Japanese Utility Model Laid-Open No. 63-174145, the number of repetitive motions of the bimetal reversing motion and the returning motion is not limited.

Furthermore, during normal operation, only a part of the spring acts, and thereafter the heat-fusible metal begins to melt or the shape-memory metal expands, further increasing the elastic force of the spring. Because of the two-stage structure in which the spring is applied, it is not necessary to increase the elastic force of the spring that is being pressed during normal operation. That is, the spring acts with a low load when repeating the normal automatic return operation, and stable operation is guaranteed for a long time.

Therefore, it is possible to prevent the situation where the operation of the bimetal itself becomes unstable due to the elastic force of the spring as seen in the prior art, and the temperature difference between the operating temperature of the bimetal and the melting point of the heat-fusible metal is not so great. Even if it is not large, it has the effect of keeping the operating temperature of the bimetal constant. Also, during normal operation, the second part of the spring is not working,
Unlike the overload protection device described in Japanese Utility Model Laid-Open No. 2-128339, there is no problem that the balance of both the first part of the spring and the second part of the spring must be taken into consideration.

Furthermore, in the event of an abnormality, a large elastic force can be obtained by the spring that operates in the second stage, so a sufficient contact dissociation distance can be secured. In other words, during the bimetal open operation in the final failure state during abnormal operation, a high load acts and the free length changes in synchronization with this, so that a sufficient contact distance can be secured.

Further, the spring load at that time can be set to an arbitrary necessary load without being limited to 400 g or the like as in the conventional structure, and the contact welding which exerts a large force can be released.

In particular, this large elastic force has an important effect that it can be applied to an overload protection device for a large current in which the contact welding force becomes large.

[0080]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 11.

[Embodiment 1] An embodiment according to the present invention will be described below with reference to FIGS. 1 to 5. First, a structure of an overload protection device according to an embodiment of the present invention and a state of a normal bimetal during operation will be described with reference to FIGS. 1 and 2.

FIG. 1 is a vertical sectional view showing an overload protection device according to an embodiment of the present invention. FIG. 2 is an enlarged vertical cross-sectional view showing a main part of a spring used in the overload protection device according to the embodiment of the present invention. FIG. 5 is a diagram illustrating in detail the structure of the adjusting screw used in the overload protection device according to the embodiment of the present invention.

The adjusting screw 6 is composed of a head portion 6a and a screw portion 6b, which are connected to each other by a heat-fusible metal 19. More specifically, the adjusting screw 6 is shown in FIG. 5 (a) or (b).
As illustrated in FIG. 2, the protrusion of the screw portion 6b is inserted into the hole of the head portion 6a, and then fixed to the bottom surface of the case 1 with the heat-fusible metal 19. The spring 20 has a shape as shown in FIG. 2, and one end of the spring 20 is fully compressed or compressed.

While being in a state close to the above, it is fixed by the heat-fusible material 21, the other end is in contact with the bimetal 5, and the bimetal 5 is constantly pressed against the head 6a of the adjusting screw 6 by the spring 20 to be held. 3, 4 are in contact with the fixed contacts 7, 8 and are closed.

The overload protection device 14 configured as described above
Are connected as shown in FIG.

In this overload protection device 14, for example, the heat-fusible material 21 may be a solder containing tin and lead as main components. The heat-fusible material 21 may have the same melting point as the same material as the heat-fusible metal 19 and may have the same melting point, or may use a component slightly lower than the melting point of the heat-fusible metal 19, or may have a slightly higher temperature. You may use a component. Further, the heat-fusible material 21 may be a chemical temperature-sensitive agent, and the combination thereof is arbitrary.

Next, the opening / closing operation of the bimetal will be described with reference to FIGS. 3 and 4. FIG. 3 is a vertical cross-sectional view showing a state in which the overload protection device according to the embodiment of the present invention is performing an automatic return operation. FIG. 4 is a vertical sectional view showing a final failure state of the overload protection device according to the embodiment of the present invention.

When an overcurrent flows through a load connected in series, the heater wire 12 heats the bimetal 5 as in the conventional example, and during the automatic recovery operation, the bimetal 5 reaches a predetermined temperature as in the conventional example. When it reaches, the bimetal 5 will be inverted and
As shown in, the movable contacts 3 and 4 are rapidly separated from the fixed contacts 7 and 8 to interrupt the circuit. Then, if the bimetal 5 repeatedly opens and closes and the movable contacts 3 and 4 are welded to each other to reach an abnormally high temperature, the heat-fusible metal 19 fixing the head portion 6a of the adjusting screw 6 is removed. To melt.

At the same time, the heat-fusible material fixing the spring 20 melts, and the pressing force increases. As a result, in the final failure mode, as shown in FIG. 4, the pushing force of the spring 20 overcomes the contact welding force and pushes up the head 6a of the adjusting screw 6 and the bimetal 5 to cut off the circuit. The spring 20 must have sufficient elastic force so that the screw head 6a and the bimetal 5 do not come into contact with the respective parts to be closed again after cooling.

In this way, the spring force other than the portion fixed by the heat-fusible material 21 acts on the normal automatic return operation (bimetal reversal movement) of the overload protection measure, and during abnormal operation (head movement). And the pushing-up operation of the bimetal, the spring force of the portion fixed by the heat-fusible material 21 is also added to act, and both stability of operation characteristics and safety are obtained in a well-balanced manner.

With respect to the structure of the present invention, the characteristics of the large current load can be opened and closed without changing the conventional structure other than the spring part and only by changing the structure of the spring. It is possible to obtain the overload protection device 14 having the same size as the conventional one, which can cut off the circuit in the event of an abnormality. Therefore,
The present invention can be applied to all overload protection devices for connecting products such as dehumidifiers and refrigerators to various electric motors such as air conditioners.

Further, it is not necessary to increase the initial load by the spring, and in addition, the joint surface area of the head and the screw portion is increased in consideration of the fact that the heat-soluble metal is distorted as the initial load increases. It is not necessary to improve the strength. As a result, a more safe overload protection device with a faster circuit interruption speed in the event of abnormal operation without causing the aforementioned operation delay due to an increase in the viscosity of the heat-fusible metal in proportion to the joint area You can do it.

[Second Embodiment] A second embodiment according to the present invention will be described below with reference to FIG. FIG. 6 is a view showing a main part of a bimetal pushing-up mechanism in which a spring structure is stacked as a first spring and a second spring.

As shown in FIG. 6, together with the conventional spring 13, a second spring 20 which is fully compressed or compressed to a state close to that is fixed to the bottom surface of the case 1 with a heat-fusible material 21 and stacked. Even if used, the same effect can be obtained.

[Embodiment 3] A third embodiment of the present invention will be described below with reference to FIG. FIG. 7 shows that the structure of the spring is stacked as a first spring and a second spring, and
FIG. 5 is a view showing a main part of a push-up mechanism of a bimetal whose spring is a shape memory alloy.

As shown in FIG. 7, the same effect as described above can be obtained by stacking the conventional spring 13 and the second shape memory spring 22 made of a shape memory alloy compressed to a state of being fully compressed or a state close to that.

As described above, even when the shape memory spring 22 is used, a good balance between normal operation and abnormal operation can be obtained as described above.

[Embodiment 4 to Embodiment 7] Another embodiment of the present invention will be described below with reference to FIGS. 8 to 11.

In the present invention, any overload protection device configured to support a bimetal via a spring can be used. That is, according to the present invention, any overload protection device can be applied regardless of its structure as long as it is configured to move its position when the temperature becomes higher than the operating temperature of the bimetal.

FIG. 8 is a vertical sectional view of an overload protection device in which the present invention is applied to the overload protection device disclosed in Japanese Patent Laid-Open No. 1-320723. FIG. 9 shows Japanese Patent Laid-Open No. 2-24445
It is a longitudinal cross-sectional view of an overload protection device to which the present invention is applied to the overload protection device disclosed in Japanese Patent No. 29. FIG. 10 is a vertical cross-sectional view of an overload protection device in which the present invention is applied to the overload protection device disclosed in Japanese Utility Model Laid-Open No. 2-128338.
FIG. 11 is a vertical sectional view of an overload protection device in which the present invention is applied to the overload protection device disclosed in Japanese Utility Model Laid-Open No. 2-128339.

As described above, the present invention can be widely applied to the overload protection device according to the prior art, and its usage range is not limited. Therefore, by adopting the present invention, each of the problems can be solved at once, and the way to put various overload protection devices into practical use can be easily and easily opened.

[0102]

As described above, according to the present invention, the structure for rapidly and permanently cutting off the electric circuit at a predetermined operating temperature and maintaining the high reliability during normal use is simple and inexpensive, and is particularly large. An overload protection device for current can be provided.

[Brief description of drawings]

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

FIG. 2 is an enlarged vertical sectional view showing a main part of a spring used in the overload protection device according to the embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view showing a state in which the overload protection device according to the embodiment of the present invention is performing an automatic return operation.

FIG. 4 is a vertical cross-sectional view showing a final failure state of the overload protection device according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating in detail the structure of an adjusting screw used in the overload protection device according to the embodiment of the present invention.

FIG. 6 is a diagram showing a main part of a bimetal pushing-up mechanism in which a spring structure is stacked as a first spring and a second spring.

FIG. 7 is a view showing a main part of a bimetal pushing-up mechanism in which a spring structure is stacked as a first spring and a second spring, and the second spring is a shape memory alloy.

FIG. 8 is a vertical cross-sectional view of an overload protection device in which the present invention is applied to the overload protection device disclosed in JP-A-1-320723.

FIG. 9 is a vertical cross-sectional view of an overload protection device in which the present invention is applied to the overload protection device disclosed in JP-A-2-244529.

FIG. 10 is a vertical sectional view of an overload protection device in which the present invention is applied to the overload protection device disclosed in Japanese Utility Model Laid-Open No. 2-128338.

FIG. 11 is a vertical sectional view of an overload protection device in which the present invention is applied to the overload protection device disclosed in Japanese Utility Model Laid-Open No. 2-128339.

FIG. 12 is a vertical sectional view showing an overload protection device described in Japanese Utility Model Publication No. 59-72641.

FIG. 13 is a plan view taken along the line BB in FIG.

FIG. 14 is a circuit diagram showing an electrical connection relationship when an overload protection device 14 ′, which is an overload protection device having a heater, is used in an electric motor.

FIG. 15 is a vertical sectional view showing an overload protection device described in Japanese Utility Model Laid-Open No. 183349/1985.

FIG. 16 is a circuit diagram showing an electrical connection relationship when an overload protection device 14 ″ which is an overload protection device without a heater is used for an electric motor.

FIG. 17 is a top view of the bimetal 5 partially broken.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Case 1a ... External bottom surface 1b ... Internal bottom surface 2 ... Lid 3,4 ... Movable contact 5 ... Bimetal 5a ... Support hole 6 ... Adjusting screw 6a ... Head 6b ... Screw part 7, 8 ... Fixed contact 9, 10 ... fixed terminal 11 ... heater terminal 12 ... heater wire 13 ... spring 14 '... overload protection device 15 ... motor 16 ... starting device 17 ... starting winding 18 ... main winding 19 ... heat fusible metal 20 ... Spring 21 ... Thermo-fusible material 22 ... Shape memory spring

Claims (7)

[Claims] 1. A bottomed cylindrical case, a disk-shaped bimetal, an adjusting screw, and a spring, wherein the adjusting screw penetrates a bottom surface of the bottomed cylindrical case, The cylindrical case includes a pair of fixed contacts, the disc-shaped bimetal has a pair of movable contacts fixed to a position facing the fixed contacts, and in a state of being in contact with one end of the spring, Supported by an adjusting screw, the spring is attached so that the central axis direction and the adjusting screw direction are aligned with each other, and the disc-shaped bimetal is pressed and held in the head direction of the adjusting screw, In an overload protection device configured to move the support position of the disc-shaped bimetal by the elastic force of the spring when the temperature becomes higher than the operating temperature of the disc-shaped bimetal, A part of the compression spring is compressed to the full compression or a state close to the compression, and a part where the adjustment screw penetrates the bottom surface of the bottomed cylindrical case and a part of the compressed spring that extends over the penetration part. An overload protection device, characterized in that it is fixed with a heat-fusible material having a melting point higher than the operating temperature of the bimetal. 2. A bottomed cylindrical case, a disk-shaped bimetal, an adjusting screw, a first spring, and a second spring, wherein the adjusting screw is the bottomed cylindrical case. The bottomed cylindrical case has a pair of fixed contacts, the disc-shaped bimetal has a pair of movable contacts fixed at a position facing the fixed contacts, and The adjustment screw is supported in a state of being in contact with one end of the first spring, the first spring is attached so that the central axis direction thereof coincides with the adjustment screw direction, and the head portion of the adjustment screw. The disc-shaped bimetal is pressed and held in a direction, and the second spring is attached so that the central axis direction and the adjusting screw direction are aligned with each other, and the second spring is heated to a temperature higher than the operating temperature of the disc-shaped bimetal. When the In an overload protection device configured such that a supporting position of a hook-shaped bimetal is moved by an elastic force of the first spring, the second spring is a direction in which a spring force of the first spring acts. In addition, the first compression spring and the second compression spring are arranged in a stacked state, and the adjustment screw penetrates the bottom surface of the bottomed cylindrical case. And the compressed second spring extending over the penetrating portion are fixed by a heat-fusible material having a melting point higher than the operating temperature of the disc-shaped bimetal. . 3. The overload protection device according to claim 1, wherein an alloy containing tin and lead as main components is used as the heat-fusible material. 4. The overload protection device according to claim 1, wherein a thermosensing agent made of a chemical substance is used as the heat-soluble material. 5. A bottomed cylindrical case, a disk-shaped bimetal, an adjusting screw, a first spring, and a second spring, wherein the adjusting screw is the bottomed cylindrical case. The bottomed cylindrical case has a pair of fixed contacts, the disc-shaped bimetal has a pair of movable contacts fixed at a position facing the fixed contacts, and The adjustment screw is supported in a state of being in contact with one end of the first spring, the first spring is attached so that the central axis direction thereof coincides with the adjustment screw direction, and the head portion of the adjustment screw. The disc-shaped bimetal is pressed and held in the direction, and the second spring is attached so that the central axis direction and the adjusting screw direction match, and when the temperature becomes higher than the operating temperature of the bimetal. , The disk-shaped vime In an overload protection device configured such that the support position of the tal is moved by the elastic force of the first spring, the second spring has a total force in the acting direction of the spring force of the first spring. Compressed or compressed to a state close to it, and further, the first spring and the second spring are stacked and arranged, and the second spring has an extension memory higher than the operating temperature of the disc-shaped bimetal. An overload protection device comprising a shape memory alloy having a temperature. 6. The overload protection device according to claim 5, wherein a non-ferrous or ferrous unidirectional material is used for the shape memory alloy. 7. The non-ferrous shape memory alloy is Ni-T.
i alloy and Cu alloy, and the iron-based shape memory alloy is
7. A stainless steel or a Cr alloy, which is characterized in that
The described overload protection device.