JP2644827B2 - Overload protection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload protection device, and more particularly to an overload protection device suitable for preventing burning of a motor winding when a bimetal break occurs.

[Conventional technology]

Generally, overload protection devices are used as means for protecting electric motors from overheating and burning, for example, in electric compressors such as refrigerators, air conditioners, and dehumidifiers, and in products that widely use electric motors.

First, an example of a conventional overload protection device is shown in FIG. 9 and FIG.
This will be described 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 line BB of FIG. As shown in the figure, in a space surrounded by a bottomed cylindrical case 1 made of a heat-resistant insulating material such as a synthetic resin and a lid 2, a disk-shaped bimetal 5 to which movable contacts 3 and 4 are fixed is placed on the bottom surface of the case 1. A first fixed terminal in which a fixed contact 7, 8 is fixed at a position facing the movable contacts 3, 4 while being pressed against a head 6 a of the shaft 6 fixedly penetrated by 1 a by a spring 13 so as to be capable of reversing. 9 and 10 are fixed through the bottom surface 1b of the case 1
A heater terminal 11 relating to a second fixed terminal is fixed through an arbitrary bottom surface 1b between the heater terminal 11 and the fixed terminal 9, and a heater wire 12 is connected between the heater terminal 11 and the fixed terminal 9 by welding or the like. The case 1 is arranged on the bottom surface 1b side of the case 1 so as to heat the bimetal 5.

As shown in FIG. 7 described later, the overload protection device P 'having such a configuration includes a parallel circuit of a starting winding 17 and a main winding 18 of a motor M in which a starting device S is connected in series, that is, a motor winding. Used to connect in series to a wire.

If any abnormality occurs in the motor M and a large restraining current flows, the self-heating of the bimetal 5 and the heater wire 12 increases, and the moment the bimetal 5 reaches the operating temperature, the bimetal 5 itself reverses rapidly and moves. The contacts 3 and 4 are separated from the fixed contacts 7 and 8, and the energization of the electric motor M is cut off.

After the power supply is cut off, the bimetal 5 and the heater wire 12 start cooling, and at the moment when the bimetal 5 reaches the reversion return temperature, the bimetal 5 performs the reverse operation reverse to the above operation, returns to the original position, and returns to the movable contact. The motors M are energized again when the fixed contacts 3 and 4 come into contact with the fixed contacts 7 and 8.

After the return, if the restrained state of the electric motor M is released, the electric motor M operates normally, and the reverse 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.

FIG. 11 is a longitudinal sectional view of another conventional overload protection device, and FIG.
FIG. 12 is an electric circuit diagram of the apparatus of FIG. 11 and FIG. 8 described later. In the figures, those having the same reference numerals as those in FIGS. 9 and 10 indicate equivalent parts.

In the overload protection device P ′ ₁ shown in FIG. 11, a disk-shaped bimetal 5 to which movable contacts 3 and 4 are fixed is penetrated and fixed to the bottom surface 1 a of the case 1 in a space surrounded by the case 1 and the lid 2. Fixed terminals 9 and 10 having fixed contacts 7 and 8 fixed at positions facing the movable contacts 3 and 4 are fixed to the bottom 6a of the case 1 while being pressed against the head 6a of the shaft 6 by a spring 13 so as to be capable of reversing. Is fixed through.

Overload protector P _'1 with such a configuration, as shown in FIG. 12, a parallel circuit or a motor winding of the starting winding 17 and primary winding 18 of the electric motor M connected to starting device S in series Used in series.

When some abnormality occurs in the electric motor M and a large restraining current flows, the amount of self-heating of the bimetal 5 increases, and the moment the operating temperature is reached, the bimetal 5 rapidly reverses. At the same time, the movable contacts 3, 4 are separated from the fixed contacts 7, 8, and the energization of the electric motor M is cut off.

After the power is turned off, the bimetal 5 starts cooling and, when the temperature reaches the reversion return temperature, performs the reversal motion reverse to the above operation and returns to the original position. At the same time, movable contacts 3 and 4 are fixed contacts
The electric motor M comes into contact again with the contacts 7, 8 and is energized again. At this time,
If the restrained state is released, the electric motor M operates normally, the current flowing through the bimetal 5 decreases, and the reversing motion of the bimetal 5 stops.

It is to be noted that Japanese Unexamined Utility Model Publication No. 60-183349, Japanese Unexamined Utility Model Application Publication No. 59-72641, and the like are known as devices of this type.

[Problems to be solved by the invention]

In the above prior art, for example, if there is some abnormality in the electric motor and the restrained state continues, the bimetal will repeat the operation and return, and eventually the bimetal will be broken by fatigue and develop contact welding. .

As a result, the motor windings generate heat and burn out. Also, a large restraining current is continuously supplied to the overload protection device, and the temperature of the bimetal rises above the heat-resistant temperature of the case and the lid, and there is a risk of burning around the bimetal.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and when the bimetal is broken due to fatigue or when contact welding occurs, the circuit is permanently interrupted, and the motor winding is removed. It is an object of the present invention to provide an overload protection device capable of preventing not only burning of the overload protection device but also that of the overload protection device.

[Means for solving the problem]

In order to achieve the above object, the configuration of the overload protection device according to the present invention includes a disk-shaped bimetal to which a movable contact is fixed in a space surrounded by a case and a lid, and the bimetal is fixed to a bottom surface of the case. A fixed terminal to which the fixed contact is fixed is fixedly penetrated to the bottom surface of the case at a position opposed to the movable contact at a position opposite to the movable contact, the pressing terminal being supported on the head side of the set shaft via a spring so as to be freely reversible. In an overload protection device in which a terminal is connected in series to a motor winding via a connection portion, a head of the shaft and the shaft are integrally formed, and a terminal is provided between the head of the shaft and the bimetal. The fusible body includes a solution, and the fusible body is configured to be deformed or melted when the temperature inside the case rises, and to move the pivotal position of the bimetal.

Note that, additionally, the overload protection device according to the present invention includes:
The melting operation temperature of the fusible material is 10 ° C to 100 ° C below the bimetal operating temperature with the load of the bimetal and spring applied.
If it is set to be within the range of plus (° C), the function is sufficiently exhibited.

[Action]

When the bimetal is fatigued, it develops into a fracture, and the bimetal inversion operation interval is shortened. Thereby, the energization time of the heater and the bimetal increases, and the temperature in the case increases. If contact welding occurs in this state, the temperature in the case further increases. At this time, when the temperature rise in the case reaches the melting temperature of the fusible body, the bimetal is pushed up toward the head of the shaft by the elastic action of the spring, and the movable contact is separated from the fixed contact.

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

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 8.

FIG. 1 is a longitudinal sectional view of an overload protection device according to one embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG.
FIGS. 2A and 2B are perspective views for explaining main parts of FIG.
FIG. 4 is a longitudinal sectional view showing a normal operation of the apparatus of FIG. 1,
FIG. 5 is an enlarged plan view of a main part showing the state of the bimetal of FIG. 1 when it is broken, and FIGS. 6 (a), (b) and (c) show the operation of the apparatus of FIG. 1 when the bimetal is broken. FIG. 7 is a longitudinal sectional view, and FIG. 7 is an electric circuit diagram of the apparatus shown in FIGS.

In the figure, those having the same reference numerals as those in FIGS.

The difference between the embodiment of FIGS. 1 and 2 and the prior art of FIGS. 9 and 10 is that the head of the shaft 6 is formed integrally with the low expansion surface side (lid 2 side) 5a of the bimetal 5 and the shaft 6. Between the part 6a and the soluble body 14
Is to intervene.

The fusible body 14 shown in FIGS. 1, 3, and 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 effect becomes more significant as the melting temperature of the fusible body 14 becomes closer to the reversal operation temperature of the bimetal 5 with the load of the bimetal 5 and the spring 13 added.

The inventors have confirmed that the following effects can be obtained by selecting the melting point of the fusible material in which the melting temperature falls within a temperature difference range of 10 ° C. to 100 ° C. plus the inversion operation temperature of the bimetal 5.

As shown in FIG. 3 (a), even if the shaft 6 is inserted through the cylindrical fusible member 14 as shown in FIG. 3 (a), as shown in FIG. Outsert molding may be formed integrally with the head 6a. In addition, the washer 14 may be provided in the soft fusible member 14 and is not affected by its structure or shape, so that an inexpensive and easy-to-assemble method can be adopted.

The pivot holes 5b of the bimetal 5 to which the movable contacts 3 and 4 shown in FIGS. 1 and 5 are fixed can be inverted when pivotally supported on the shaft 6 and can be moved toward the lid 2 side. The diameter is slightly larger than the diameter.

Further, as shown in FIG. 5, the slits 5c provided radially from the shaft supporting hole 5b are
It is formed so as to disperse the stress generated in 5b.

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

If any abnormality occurs in the motor M and a large restraining 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 reversing operation temperature, the bimetal 5 itself rapidly reverses. As shown in FIG. 4, the movable contacts 3, 4 are separated from the fixed contacts 7, 8, and the energization of the electric motor M is cut off.

After the power supply is cut off, the bimetal 5 and the heater wire 12 start cooling, and at the moment when the bimetal 5 reaches the reversion return temperature, the bimetal 5 performs the reverse operation reverse to the above operation, returns to the original position, and returns to the movable contact. The motors M are energized again when the fixed contacts 3 and 4 come into contact with the fixed contacts 7 and 8.

After the return, if the restrained state of the motor M is released, the motor M operates normally, and the reversing motion of the bimetal 5 stops here.

However, while the constrained state is continuing and the bimetal 5 repeatedly performs the reversing motion of the operation and the return, the bimetal 5 is fatigued and breaks as shown by E and F in FIG. Then, the reversal operation interval of the bimetal 5 is shortened due to a change in the reversal operation temperature and the reversion return temperature of the bimetal 5 or a decrease in the reversal operation amount.

As a result, the duty ratio of the constraint current flowing through the bimetal 5 and the heater wire 12 increases, and the temperature in the case 1 increases.

At this time, when the temperature of the fusible body 14 interposed at the head of the shaft 6 reaches a temperature near the melting point of the fusible body,
Is deformed in compression without being able to resist the elasticity of the spring 13. The bimetal 5 moves in the direction of the head 6a of the shaft 6 by the elastic action of the spring 13 by the amount of compressive deformation of the fusible member 14.

As shown in FIG. 6 (a), when this position movement reaches a position where the movable contacts 3, 4 and the fixed contacts 7, 8 cannot contact each other, the circuit is interrupted. Further, it goes without saying that since the bimetal 5 is kept pushed up by the spring 13, the open state is continued.

Further, assuming that contact welding occurs during this process, when the bimetal 5 is broken, the characteristics itself of the bimetal 5 change significantly, and the movable contact 3
The operating force on the side where the movable contact 4 is fixed is imbalanced with the side where the movable contact 4 is fixed. Therefore, the contact welding is concentrated on one contact side which directly opens and closes the load. When contact welding occurs, the constrained current is continuously supplied, and the temperature in the case 1 rises rapidly. At this time, the fusible body 14 melts instantaneously, and the elasticity of the spring 13 causes the bimetal 5 to start moving in the direction of the head 6 a of the shaft 6.

For example, as shown in FIG. 6 (b), if the movable contact 3 side is welded, the bimetal 5 to which one of the non-welded movable contacts 4 is fixed moves independently with the break, thereby breaking the circuit. .

At this time, if a shear force acts on the welding point of the movable contact 3 and the elasticity of the spring 13 overcomes, the movable contact 3 side also cuts off the circuit, and the bimetal 5 is in a horizontal state as shown in FIG. Is held.

Further, in this embodiment, even if the bimetal 5 moves in the direction of the lid 2, the movement is regulated by the operation effect of the head 6 a of the shaft 6 formed integrally with the shaft 6, and the bimetal 5 is moved from the shaft 6. There is no short-circuit accident such as detachment and contact with the fixed contacts 7, 8 or the heater 12, or secondary disaster such as insulation failure due to contact with the lid 2.

As the material of the fusible material, various materials can be applied as described above, and the operating temperature range is not limited, so that there is an effect that an overload protection device having a wide range of temperature characteristics can be provided.

Further, since an operation such as soldering is not required at the time of assembly, there is an effect that a device having a stable operating temperature can be obtained.

As described above, according to the present embodiment, the bimetal is fatigued and damaged, and the circuit is completely cut off before contact welding occurs, so that not only the motor winding but also the overload protection device can be completely burnt. Overload protection device that can be prevented.

In this embodiment, even if contact welding occurs, it can be forcibly removed, 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.

8, the same reference numerals as those in FIG. 11 denote the same parts as those in the prior art, and a description thereof will be omitted.

In addition, the same parts as those in the embodiment of FIGS. 1 and 2 are denoted by the same reference numerals.

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

Such overload protector P ₁ configuration, as shown in FIG. 12, the bimetal 5 and a motor M are connected in series.

Actuation of the bimetal 5 in overload protector P ₁ when any abnormality occurs in the motor M is the same as the previous embodiment.

If the bimetal 5 is fatigued and breaks while the bimetal 5 repeatedly performs the reversing motion of the operation and the return, the same phenomenon as in the previous embodiment occurs.

As a result, the duty ratio of the bimetal 5 increases, and the case 1
The temperature inside is increased, and the fusible member 14 is operated in the same manner as in the previous embodiment.

Therefore, according to the embodiment shown in FIG. 8, the same effects as those of the embodiment shown in FIGS.

Also, unlike the previous embodiment, the function of the washer 15 prevents the fusible member 14 from being worn by the reversing operation of the shaft supporting hole 5b of the bimetal 5, and has a unique effect that the operation and return temperatures are stabilized for a long time. .

〔The invention's effect〕

As described above, according to the present invention, when the bimetal is broken due to fatigue or when contact welding occurs, the circuit is permanently interrupted, and the overload protection device as well as the motor winding is damaged. An overload protection device that can prevent burnout of a battery can be provided. Furthermore, the bimetal does not come off even when the fusible material melts due to the head formed integrally with the shaft. And since the fusible body is only provided between the head of the shaft and the bimetal, the work of fixing the head by soldering when the head of the shaft is separate is unnecessary, and the bimetal and the head by soldering are unnecessary. In this way, there is no variation in dimensions between the two, and a device with a stable operating temperature can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an overload protection device according to one embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIGS. FIG. 4 is a perspective view illustrating a main part of FIG. 1, FIG. 4 is a longitudinal sectional view showing a normal operation of the apparatus of FIG. 1, and FIG. 6 (a), (b) and (c) are longitudinal sectional views showing the operation of the apparatus shown in FIG. 1 when the bimetal is broken, and FIG.
1 and 9 are electric circuit diagrams, FIG. 8 is a longitudinal sectional view of an overload protection device according to another embodiment of the present invention, and FIG. 9 is a longitudinal section of a conventional overload protection device. Fig. 10
FIG. 9 is a sectional view taken along the line BB of FIG. 9, FIG. 11 is a longitudinal sectional view of another conventional overload protection device, and FIG. 12 is an electric circuit diagram of the device of FIGS. 11 and 8. . 1 ... Case 2, 2 ... Lid 3,4 ... Movable contact, 5 ... Bimetal 6 ... Shaft, 6a ... Head 7,8 ... Fixed contact, 9,10 ... Fixed terminal 13 ... Spring , 14 …… soluble

Claims (3)

(57) [Claims] 1. A disk-shaped bimetal to which a movable contact is fixed is provided in a space surrounded by a case and a lid, and the bimetal is reversible via a spring on a head side of a shaft fixed to a bottom surface of the case. A fixed terminal to which the pressing contact is supported and the fixed contact is fixed at a position facing the movable contact is fixedly penetrated to the bottom surface of the case, and the fixed terminal is connected in series to the motor winding through a connection portion. In such an overload protection device, the head of the shaft and the shaft are integrally formed, and a fusible body is provided between the head of the shaft and the bimetal. An overload protection device characterized in that the overload protection device is configured to be deformed or melted to move a bimetallic support position. 2. The overload protection device according to claim 1, wherein the fusible body is formed in a cylindrical shape, and a shaft is inserted into a hole on the inner diameter side of the cylindrical shape. 3. The overload protection device according to claim 1, wherein the fusible body is outsert molded on the head side of the shaft and integrated with the shaft.