JPH01320723A - overload protection device - Google Patents

Abstract

PURPOSE:To prevent burnings of a motor winding and a device at the time of a bimetal failure by interposing a fuse-element between the heat of an axis for fixing the bimetal and the bimetal so as to shift the axis supporting position at the time of a temperature rise inside a case. CONSTITUTION:When a bimetal 5 is fatigued, it develops into rupture, and interval between the inserting operation is shortened. Hereby, current application time between the heater 12 and the bimetal 5 increases and elevates the temperature inside the case 1. When contact welding occurs in this condition, the temperature inside the case rises further. When the temperature rise at this time reaches the fusing temperature of a fuse-element 14, by the elastic action of a spring 13 the bimetal 5 is pushed up in the direction of the head 6a of an axis 6, and movable contacts 3 and 4 separate from fixed contacts 7 and 8. Thereafter, the fuse-element 14 solidifies at the position whore the bimetal 5 is pushed up by the spring 13, and is maintained at that position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overload protection device, and particularly to an overload protection device suitable for preventing burnout of motor windings when a bimetal rupture occurs.

[Conventional technology]

Generally, overload protection devices are used in a wide range of products that use electric motors, including electric compressors such as refrigerators, air conditioners, and dehumidifiers, as a means to protect the electric motor from overheating and burnout.

First, an example of a conventional overload protection device is shown in Figures 9 and 1.
This will be explained with reference to FIG.

FIG. 9 is a longitudinal sectional view of a conventional overload protection device, and FIG. 10 is a sectional view taken along the line BB in FIG. As shown in the figure, a disc-shaped bimetal 5 to which movable contacts 3 and 4 are fixed is placed in a space surrounded by a bottomed cylindrical case 1 made of a heat-resistant insulating material such as synthetic resin and a lid 2, on the bottom surface of the case 1. A first fixed terminal is pressed by a spring 13 to the head 6a of a shaft 6 which is fixed through the shaft 1a, and is pivotably supported in a freely reversible manner, and fixed contacts 7 and 8 are fixed at positions facing the movable contacts 3 and 4. 9 and 10 are fixed through the bottom surface 1b inside the case 1, and any bottom surface 1 between the fixed terminal 9 and the fixed terminal 10 is fixed.
In b, a heater terminal 11 related to a second fixed terminal is fixed through the case 1, and a heater wire 12 is connected by welding or the like between this heater terminal 11 and the fixed terminal 9, and the bimetal 5 is heated. It was placed on the bottom lb side.

The overload protection device y having such a configuration includes a motor M having a starter device 8 connected in series, as shown in Figure 7, which will be described later.
The starting winding 17 and main winding 18 of the motor are connected in parallel and in series in a circuit, that is, a motor winding.

When some kind of abnormality occurs in the electric motor M and a large restraint current flows, the self-heating of the bimetal 5 and the heater wire 12 increases, and the moment the bimetal 5 reaches its operating temperature, the bimetal 5 itself rapidly reverses motion and becomes movable. The contacts 3 and 4 are separated from the fixed contacts 7 and 8, and the electric motor M is de-energized.

After the current is cut off, the bimetal 5 and the heater wire 12 start cooling, and at the moment when the reversal return temperature is reached, the bimetal 5 performs a reversal operation that is the opposite of the above operation, returns to its original position, and the movable contact 3 and 4 contact the fixed contact 7°8 and the electric motor M
is energized again.

After the return, if the restraint state of the electric motor M is released,
The electric motor M operates normally, and the reversal movement of the bimetal 5 stops here.

Next, another example of the conventional overload protection device will be described with reference to FIGS. 11 and 12.

FIG. 11 is a longitudinal sectional view of another conventional overload protection device, and FIG. 12 is an electric circuit diagram of the device shown in FIG. 11 and FIG. 8, which will be described later. In the figure, the same reference numerals as in the previous figures 9 and 10 indicate the same parts.

The overload protection device P1 shown in FIG. 11 consists of a case 1 and a lid 2.
A disk-shaped bimetal 5 to which the movable contacts 3 and 4 are fixed is pushed by a spring 13 to the head 6'a of a shaft 6 fixed to the bottom surface 1a of the case 1, so that it can be rotated freely. Fixed terminals 9 and 1 are pivotably supported by the fixed terminals 9 and 1 and fixed contacts 7 and 8 are fixed at positions facing the movable contacts 3 and 4.
0 is fixed through the bottom surface 1a of the case 1.

As shown in FIG. 12, the overload protection device P1 having such a configuration includes a parallel circuit of the starting winding 17 and the main winding 18 of the motor M in which the starting device S is connected in series, that is, the motor winding. Used by connecting in series.

When some kind of abnormality occurs in the electric motor M and a large restraint current flows, the amount of self-heating of the bimetal 5 increases, and the moment the bimetal 5 reaches its operating temperature, the bimetal 5 undergoes a rapid reverse movement.

At the same time, the movable contacts 3, 4 separate from the fixed contacts 7.8, and the electric motor M is de-energized.

After the electricity is cut off, the bimetal 5 starts cooling and at the moment it reaches the inversion return temperature, it performs an inversion movement that is the opposite of the above operation and returns to its original position. At the same time, the movable contacts 3, 4 come into contact with the fixed contacts 7, 8, and the electric motor M is energized again. At this time, if the restraint state is released, the electric motor M will operate normally,
The current flowing through the bimetal 5 decreases and the reverse movement of the bimetal 5 stops.

Incidentally, related devices of this type include, for example, Japanese Utility Model Application Publication No. 183349/1983 and Japanese Utility Model Application No. 7264/1989.
Publication No. 1 etc. are known.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, for example, if there is some abnormality in the electric motor and the locked state continues, the bimetal will repeatedly operate and return, and eventually the bimetal will fatigue and break, leading to contact welding. .

As a result, the motor windings generate heat and burn out. Further, a large restraining current is continuously applied to the overload protection device, and the temperature of the bimetal rises above the heat-resistant temperature of the case and the lid, which may cause burnout of the area around the bimetal.

The present invention was made in order to solve the above-mentioned problems of the prior art, and when the bimetal fatigues and breaks, or when contact welding occurs, the circuit is permanently interrupted and the motor windings are It is an object of the present invention to provide an overload protection device that can prevent burnout of the overload protection device as well as burnout of the overload protection device.

[Means to solve the problem]

In order to achieve the above object, the overload protection device according to the present invention has a configuration in which a disc-shaped bimetal having a movable contact fixed thereon is provided in a space surrounded by a cylindrical case with a bottom, and this bimetal is attached to the case. A shaft fixed to the bottom surface is rotatably supported via a spring on the head side thereof, and a fixed terminal having a fixed contact fixed thereto is penetrated and fixed to the bottom surface of the case at a position facing the movable contact. In addition, in the overload protection device in which the fixed terminal is connected in series to the motor winding via the connection part, a fusible material is interposed between the head of the shaft and the bimetal to prevent temperature rise inside the case. Sometimes, the fusible body is deformed or melted to move the pivot position of the bimetal.

Additionally, in the overload protection device according to the present invention, the melting operating temperature of the fusible body is 10°C to 10°C lower than the bimetal operating temperature when the bimetal and the spring load are applied.
If it is set within the range of 0°C plus, it will fully demonstrate its function.

[Effect]

When the bimetal fatigues, it develops into fracture, and the interval between reversal operations of the bimetal becomes shorter. This increases the energization time of the heater and bimetal, raising the temperature inside the case. Furthermore, if contact welding occurs in this state, the temperature inside the case will further rise. At this time, when the temperature rise inside the case reaches the melting temperature of the fusible material, the bimetal is pushed up toward the head of the shaft by the elastic action of the spring, and the movable contact separates from the fixed contact.

Thereafter, the soluble material of the bimetal solidifies at the position pushed up by the spring, and is held in that position. As a result, re-energization of the motor windings does not occur, and it is possible to prevent not only the motor windings from burning out but also the overload protection device from burning out.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 8.

FIG. 1 is a longitudinal sectional view of an overload protection device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIGS. FIG. 4 is a vertical sectional view showing the device in FIG. 1 in normal operation; FIG. 5 is an enlarged view of the main part in FIG. 1 when the bimetal is broken. Plan view, Figures 6(a) and (b).

(c) is a longitudinal cross-sectional view showing the operation of the device shown in FIG. 1 when the bimetal breaks, and FIG. 7 is an electric circuit diagram of the devices shown in FIGS. 1 and 9.

In the drawings, parts with the same symbols as those in Figs. 9 and 10 are the same parts as in the prior art, so their explanation will be omitted.

The difference between the embodiment shown in FIGS. 1 and 2 and the prior art shown in FIGS. 9 and 10 is that the low expansion surface side (lid 2 side) of the bimetal 5 5
The fusible body 14 is interposed between the shaft 6 and the head 6a of the shaft 6.

The fusible body 14 shown in FIG. 1.3.4 may be, for example, a low melting point metal material such as tin, or a synthetic resin material such as a thermosensitive pellet.

The closer the melting temperature of the fusible body 14 is to the reversal operation temperature of the bimetal 5 with the load of the bimetal 5 and the spring 13 applied, the more effective the effect will be.

The inventors have confirmed that the effects described below can be obtained by selecting the melting point of the fusible material such that the melting temperature ranges from 10° C. to 100° C. above the reversal operating temperature of the bimetal 5. - Even if the shaft 6 is inserted through the cylindrical fusible body 14 as shown in FIG. 3(a), the fusible body 14 cannot be inserted into the shaft 6 as shown in FIG. The head 6a may be integrally externally molded.Also, a washer 15 may be provided in the case of the soft fusible body 14, and the structure and shape of the washer 15 are not affected, so this method is inexpensive and easy to assemble. can be adopted.

The shaft support hole 5b of the bimetal 5 to which the movable contact 3.4 shown in FIGS. It is formed to a diameter slightly larger than the diameter.

Further, as shown in FIG. 5, slits 5c provided radially from the shaft support hole 5b are formed to disperse stress generated in the shaft support hole 5b when the bimetal 5 is reversed.

In the overload protection device P having such a configuration, as shown in FIG. 7, the bimetal 5, the heater wire 12, and the electric motor M are connected in series. Thereby, the overload protection device P is connected in series to the parallel circuit of the starting winding 17 and the main winding 18 of the motor M to which the starting device S is connected in series, that is, to the motor winding.

When some kind of abnormality occurs in the electric motor M and a large restraint current flows, the amount of self-heating of the bimetal 5 and the heater wire 12 increases, and the moment the bimetal 5 reaches the reversal operating temperature, the bimetal 5 itself suddenly undergoes a reversal movement. , as shown in FIG. 4, the movable contact 3.4 separates from the fixed contact 7.8, and the current to the motor M is cut off.

After the current is cut off, the bimetal 5 and the heater wire 12 start cooling, and at the moment when the reversal return temperature is reached, the bimetal 5 performs a reversal operation that is the opposite of the above operation, returns to its original position, and the movable contact 3 and 4 contact the fixed contact 7°8 and the electric motor M
is energized again.

After recovery, if the restraint state of electric motor M is released, electric +
tNM operates normally and the reversal movement of the bimetal 5 stops here.

However, while the restraint state continued and the bimetal 5 was repeatedly performing reverse movements of movement and return, the bimetal 5 became fatigued and broke as shown at 113 and F in Fig. 5. Then, due to a change in the reversal operation temperature and reversal return temperature of the bimetal 5, or a decrease in the amount of reversal operation, the interval between the reversal operations is shortened.

As a result, the energization rate of the restrained current flowing through the bimetal 5 and the heater wire 12 increases, and the temperature inside the case 1 increases.

At this time, when the temperature of the fusible body 14 interposed in the head of the shaft 6 reaches a temperature near the melting point of the fusible body, the fusible body 14
cannot resist the elasticity of the spring 13 and is compressed and deformed. The bimetal 5 is moved in the direction of the head 6a of the shaft 6 by the amount of compressive deformation of the fusible body 14 due to the elastic action of the spring 13.

When this positional movement reaches a position where the movable contacts 3, 4 and the fixed contacts 7.8 cannot contact each other, as shown in FIG. 6(a), the circuit is broken. Furthermore, since the bimetal 5 remains pushed up by the spring 13, it goes without saying that the open circuit state continues.

Furthermore, if we assume that contact welding has occurred during this process, in the state where the bimetal 5 is broken, the characteristics of the bimetal 5 itself will change significantly, and the side where the movable contact 3 is fixed and the movable contact 4 The operating force on the side that is stuck becomes unbalanced. Therefore, contact welding occurs concentratedly on the one contact side that directly switches and closes the load. When contact welding occurs, the restraining current becomes continuous, and the temperature inside the case 1 rises rapidly. At this time, the fusible body 14 melts instantly, and the bimetal 5 starts to move in the direction of the head 6a of the shaft 6 due to the elasticity of the spring 13.

For example, as shown in FIG. 6(b), if the movable contact 3 side is welded, the bimetal 5 that fixed the movable contact 4, which is not welded, breaks and moves independently, breaking the circuit. .

At this time, if a shearing force acts on the welding point of the movable contact 3 and overcomes the elasticity of the spring 13, the movable contact 3 side also breaks the circuit, and the bimetal 5 is in a horizontal state as shown in FIG. 6(C). is maintained.

Further, in this embodiment, even if the bimetal 5 moves in the direction of the lid 2, the movement is regulated by the head 6a of the shaft 6, and the bimetal 5 separates from the shaft 6 and the fixed contacts 7, 8 or the heater 12 There is no risk of short-circuit accidents such as contact with the lid 2, or secondary disasters such as poor insulation due to contact with the lid 2.

As mentioned above, various materials are suitable for the soluble material.
Since the temperature range for use is not limited, it is possible to provide an overload protection device having a wide range of temperature characteristics.

Furthermore, since work such as soldering is not required during assembly, it is possible to obtain a device with a stable operating temperature.

As described above, according to the non-implemented example, the circuit is completely cut off before the bimetal is fatigued and damaged and contacts weld, and the burnout of the overload protection device as well as the motor windings is completely prevented. An overload protection device can be provided to prevent overload.

In addition, in this embodiment, even if contact welding occurs, it is possible to forcibly remove it, and a highly reliable overload protection device can be provided.

Next, FIG. 8 is a longitudinal sectional view of an overload protection device according to another embodiment of the present invention.

In FIG. 8, the same reference numerals as those in FIG. 11 are the same parts as in the prior art, so the explanation thereof will be omitted.

Further, parts equivalent to those in the embodiment shown in FIGS. 1 and 2 are designated by the same reference numerals.

The embodiment shown in FIG. 8 differs from the prior art shown in FIGS. 11 and 12 in that a fusible body 14 and a washer 15 are added. The difference from the embodiments shown in FIGS. 1 and 2 is that there is no heater wire.

In the overload protection device P having such a configuration, as shown in FIG. 12, the bimetal 5 and the electric motor M are connected in series.

The operation of the bimetal 5 of the overload protection device P1 when some abnormality occurs in the electric motor M is the same as in the previous embodiment.

If the bimetal 5 fatigues and breaks while the bimetal 5 is repeatedly performing reverse movements of operation and return while the above-mentioned restraint state continues, the same phenomenon as in the previous embodiment will occur.

As a result, the energization rate of the bimetal 5 increases, the temperature inside the case 1 increases, and the fusible body 14 operates in the same manner as in the previous embodiment.

Therefore, according to the embodiment shown in FIG. 8, effects exactly the same as those of the previous embodiment shown in FIGS. 1.2 can be achieved.

Further, unlike the previous embodiment, due to the function of the washer 15, the fusible body 14 does not wear out due to the reversal movement of the shaft support hole 5b of the bimetal 5, and the operation and return temperature are stabilized for a long period of time, which is a unique effect. .

〔Effect of the invention〕

As described above, according to the present invention, when the bimetal fatigues and breaks, or when contact welding occurs, the circuit is permanently interrupted, and the overload protection device prevents burnout of the motor windings as well as It is possible to provide an overload protection device that can prevent burnout.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an overload protection device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIGS. FIG. 4 is a vertical sectional view showing the device in FIG. 1 in normal operation; FIG. 5 is an enlarged view of the main part in FIG. 1 when the bimetal is broken. 6 (a) l (b). (c) is a longitudinal sectional view showing the operation of the device in FIG. 1 when the bimetal breaks, and FIG. 7 is the device in FIGS. 1 and 9. 8 is a longitudinal sectional view of an overload protection device according to another embodiment of the present invention, FIG. 9 is a longitudinal sectional view of a conventional overload protection device, and FIG. 10 is a longitudinal sectional view of a conventional overload protection device. A sectional view taken along the line B-B in Figure 9,
FIG. 11 is a longitudinal sectional view of another conventional overload protection device, and FIG. 12 is an electrical circuit diagram of the devices shown in FIGS. 11 and 8. Case 2...Lid 3.4...Movable contact 5...Bimetal 6...
・Shaft 6a...Head 7.8...Fixed contact 9,10...Fixed terminal 13...Spring
14... Fusible Agent 5P Burial Officer Katsutoshi Ogawa 9＼Advisor 4 Yoto = Mamoru 6th Ward Sun Station Practice b"(S")

Claims (1)

[Claims] 1. A disk-shaped bimetal with a movable contact fixed is provided in a space surrounded by a cylindrical case with a bottom, and this bimetal has a spring attached to the head side of a shaft fixed to the bottom of the case. A fixed terminal is rotatably supported through the case and has a fixed contact fixed thereto at a position opposite to the movable contact, and is fixed through the bottom of the case, and the fixed terminal connects to the motor windings through the connection part. The overload protection device is connected in series to the bimetal, and the overload protection device includes a fusible body interposed between the head of the shaft and the bimetal, and the fusible body deforms or melts when the temperature inside the case rises. An overload protection device characterized in that the overload protection device is configured to move the pivot position of the bimetal. 2. The overload protection device according to claim 1, characterized in that the fusible body is made of a metal material whose melting temperature is 10 to 100 degrees Celsius above the reversal temperature of the bimetal. . 3. Overload protection according to claim 1, characterized in that the fusible body is made of a synthetic resin material whose melting temperature is 10 to 100 degrees Celsius above the reversal temperature of the bimetal. Device. 4. An overload protection device according to any one of claims 1 to 3, characterized in that the fusible body is formed into a cylindrical shape, and a shaft is inserted into the hole. 5. An overload protection device according to any one of claims 1 to 3, characterized in that a fusible material is externally molded around the shaft and integrated with the shaft. 6. An overload protection device according to any one of claims 1 to 5, characterized in that a washer is provided between the fusible body and the bimetal.