JPH012232A - overload protection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 that is suitable for preventing burnout of motor windings when contact welding occurs. It is.

[Conventional technology]

First, an example of a conventional overload protection device is shown in Figures 8 and 9.
This will be explained with reference to the figures.

FIG. 8 is a longitudinal sectional view of a conventional overload protection device.

FIG. 9 is a sectional view taken along the line B-B in FIG. 8.

As shown in the figure, a movable contact 3 is placed in a space surrounded by a bottomed cylindrical case 1 made of heat-resistant insulating material such as synthetic resin and a lid 2.
．． A disk-shaped bimetal 5 to which 4 is fixed is attached to case 1.
A first fixed terminal 9.10 is rotatably supported by a shaft 6 fixed to the bottom surface 1a of the case 1, and has a fixed contact 7.8 fixed at a position facing the movable contact 3.4. A heater terminal 11 related to the second fixed terminal is fixed through the bottom surface 1b of the second fixed terminal, and a heater terminal 11 related to the second fixed terminal is fixed through the bottom surface 1b between the fixed terminal 9 and the fixed terminal 10. A heater wire 12' was connected to the terminal 9 by welding or the like, and was placed on the bottom lb side of the case 1 so as to heat the bimetal 5.

The overload protection device P' having such a configuration is the fourth one described later.
As shown in the figure, an electric motor M with a starter S connected in series
The starter winding 17 and the main winding 18 are connected in series in a parallel circuit, that is, in 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 moves in reverse, The movable contact 3.4 separates from the fixed contact 7.8, and the electric motor M is de-energized.

After the power supply 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 operation described above, and returns to its original position. The movable contact 3.4 contacts the fixed contact point 7.8 and the 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 a conventional overload protection device will be described with reference to FIGS. 10 and 11.

FIG. 10 is a longitudinal sectional view of another conventional overload protection device, and FIG. 11 is an electrical circuit diagram of the device shown in FIG. In the figure,
The same reference numerals as in the previous Fig. 8.9 indicate equivalent parts.

The overload protection device shown in FIG. 10 has a shaft 6 fixed to the bottom surface 1a of the case 1 through a disc-shaped bimetal 5 to which a movable contact 3.4 is fixed, in a space surrounded by the case 1 and the lid 2. The movable contact 3.
A fixed terminal 9.10 having a fixed contact 7.8 fixed at a position opposite to the fixed terminal 9.1 is fixed to the bottom surface 1a of the case 1 through the fixed terminal 9.10.

As shown in FIG. 11, the overload protection device r having such a configuration includes a 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, 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 contact 3.4 separates from the fixed contact 7.8, and the electric motor M is de-energized.

After the current 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 contact 3.4 comes into contact with the fixed contact 7.8 and the 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 that the invention seeks to solve]

In the above-mentioned conventional technology, for example, if there is some kind of 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 to solve the problems of the prior art described above, and when the bimetal is fatigued and damaged and contacts weld, one circuit is completely cut off, and the motor windings are not burnt out. It is an object of the present invention to provide an overload protection device that can completely prevent burnout of the overload protection device.

[Means for solving problems]

In order to achieve the above object, the overload protection device according to the present invention has a structure in which a cylindrical case with a bottom is surrounded by a lid.
A disk-shaped bimetal having a movable contact fixed to it is rotatably supported by a shaft penetrating and fixed to the bottom of the case, and a first fixed terminal having a fixed contact fixed to a position facing the movable contact is attached to the case. Fixed through the bottom,
Further, in the overload protection device, a second fixed terminal is provided on the bottom surface of the case, and these first and second fixed terminal parts are connected in series to the motor winding via a connecting part,
A phase means is provided at the connection portion between the first fixed terminal and the second fixed terminal.More specifically, the second fixed terminal is a heater terminal, and the heater terminal and the first fixed terminal are connected to each other. A thin wire portion is provided in a part of the heater wire to be connected.

Additionally, the overload protection device according to the present invention focuses on the fact that when the contacts are welded, the temperature inside the case becomes higher than when the bimetal is in normal operation. A temperature phase having a humidity temperature of Qi is connected and arranged in series with a bimetal.

[Effect]

To describe the function of the above technical means, when contact welding occurs, one thin wire section provided in the heater wire generates heat and melts, or the temperature inside the case rises and the melting temperature of the temperature phase increases. By the function of the phase means, such as cutting off the current supply to the motor windings when the temperature reaches 1, it is possible to prevent not only the motor windings from burning out but also the overload protection device from burning out. An example will be explained with reference to FIGS. 1 to 7.

First, FIG. 1 is a longitudinal sectional view of an overload protection device according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line A-A in FIG. 1.
FIG. 3 is an enlarged view showing an example of the shape of the am section of the heater wire shown in FIG. 2, and FIG. 4 is an electrical circuit diagram of the device shown in FIG. 1.

In the drawings, parts with the same symbols as in Figs. 8 and 9 are the same parts as in the prior art, so their explanations will be omitted.

The difference between the embodiment shown in FIG. 1.2 and the prior art shown in FIG. 8.9 is that the first fixed terminal 9 and the second fixed terminal are fixedly provided through the bottom surface 1a of the case 1. This is because a thin wire portion 13 having a small cross-sectional area relating to the phasing means is provided in a part of the heater wire 12 connected between the heater terminal 11 and the heater terminal 11.

The thin wire portion 13 of the heater wire 12 is shown in FIGS. 3(a) to 3(c).
) is formed as shown. That is, Fig. 3 (a
) has a cut groove 14 formed therein, and
The one shown in FIG. 3(b) has a constricted portion 15, and the one shown in FIG. 3(c) has a collapsed portion 16, both of which have a small cross-sectional area.

In the overload protection device P having such a configuration, as shown in FIG. 4, the bimetal 5, the heater wire 12, and the electric motor M are connected in series. As a result, the overload protection device P
It is used by connecting in series to a parallel circuit of a starting winding 17 and a main winding 18 of a motor M to which a starting device S is connected in series, that is, a motor winding.

If some abnormality occurs in the electric motor M and a large restraint current flows, the self-9 of the bimetal 5 and the heater wire 12
! At the moment when the amount of heat increases and the bimetal 5 reaches the operating temperature, the bimetal 5 itself suddenly moves in reverse, causing the movable contact 3.
4 is separated from the fixed contact 7.8, and the current to the electric 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 3.4 contacts 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.

However, if the restrained state continues and the bimetal 5 fatigues and breaks while the bimetal 5 repeatedly performs reverse movements of movement and return, and contact welding occurs, the bimetal 5 becomes continuously energized. As a result, a large constraint current also continuously flows through the heater wire 12 connected in series to the bimetal 5. As a result, the entire heater wire 12 becomes hotter than when the bimetal 5 is in normal operation.

Since the thin wire portion 13 of the heater wire 12 has a small cross-sectional area and a large resistance value, it locally generates heat and reaches a higher temperature than other portions. The temperature reached at this time is determined by the thin wire portion 13.
If the temperature is set higher than the fusing temperature, the thin wire portion 13 will be fused and the electric motor M will be de-energized.

Therefore, according to this embodiment, the electric motor M will not be burnt out due to continuous energization, and the case of the overload protection device P will not be burnt out due to heat generated by continuous energization of the heater wire 12.

Further, since a highly safe overload protection device can be provided simply, inexpensively, and without making major changes to the conventional structure, its practical effects are significant.

Next, FIG. 5 is a partial cross-sectional view of an overload protection device according to another embodiment of the present invention, and FIG. 6 is a cross-sectional view taken along the line CC in FIG.
FIG. 7 is an electrical circuit diagram of the device of FIG.

In the drawings, the same reference numerals as those in Figs. 10 and 11 are the same parts as in the prior art, so the explanation thereof will be omitted. Also, the first
．． Components equivalent to those in the embodiment shown in FIG. 2 are designated by the same reference numerals.

The difference between the embodiment shown in Fig. 5.6 and the prior art shown in Fig. 10.11 or the embodiment shown in Fig. 1.2 is that case 1
A temperature phase 21 related to the phase means is provided between the terminal 20 related to the second fixed terminal provided penetratingly fixed to the bottom surface 1a of the 1st fixed terminal 9, and the temperature phase 21 related to the phase means.
The reason for this is that the fusing temperature is set higher than the temperature inside the case 1 during the reversal operation of the bimetal 5.

In the overload protection device P having such a configuration, as shown in FIG. 7, the bimetal 5, the temperature phase 21, and the electric motor M are connected in series.

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

The above-mentioned restraint state continues and the bimetal 5 operates,
If contact welding occurs while the reversal motion of return is being repeated, the bimetal 5 will be continuously energized.

As a result, the heat generation energy of the bimetal 5 increases and the temperature inside the case 1 rises, and when the temperature reaches the melting temperature of the temperature phase 21, the temperature phase 21 is melted and the electric motor M is de-energized.

Therefore, according to the embodiment shown in FIG. 5.6, the first embodiment described above.
Exactly the same effects as the embodiment shown in FIG. 2 are expected.

〔Effect of the invention〕

As described above, according to the present invention, when the bimetal is fatigued and damaged and contact welding occurs, the circuit is completely cut off, and the burnout of the overload protection device as well as the motor windings is completely prevented. It is possible to provide an overload protection device that can prevent

[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 FIG. 3 is a heater shown in FIG. 2. FIG. 4 is an enlarged view showing an example of the shape of a thin line portion, and FIG. 4 is an electrical circuit diagram of the device shown in FIG. 1. FIG.
FIG. 6 is a partial sectional view of an overload protection device according to another embodiment of the present invention; FIG. 6 is a sectional view taken along the line C-C in FIG. 5; FIG. 9 is a longitudinal sectional view of a conventional overload protection device, FIG. 9 is a sectional view taken along the line B-B in FIG. 8, and FIG. 1
FIG. 1 is an electrical circuit diagram of the device of FIG. 10. 1... Case, 2... Lid, 3.4... Movable contact,
5... Bimetal, 6... Shaft, 7.8... Fixed contact, 9.10... Fixed terminal, 11... Heater terminal,
12... Heater wire, 13... Cutting line portion, 14... Cut groove, 15... Constricted portion, 16... Crushed portion, 1
7... Starting winding, 18... Main winding, 20... Terminal, 21... Temperature phase. ! , Agent Patent Attorney Katsuo Ogawa -1/ ¥: 1 B Stem 2 Mouth 6/Shaft 13,8 Tianshoku Kyoiho 3 Figure \2, (b) No. 41!1 '45 Mouth 21-5已, the role of Fuyu dog. Stem q Figure Convex Stem 9th Day 10 Figure Stem 11 Figure

Claims (1)

[Scope of Claims] 1. In a space surrounding a bottomed cylindrical case with a lid, a disc-shaped bimetal having a movable contact fixed thereon is rotatably supported by a shaft fixed through the bottom of the case, and
a first fixed contact fixed to a position facing the movable contact;
A fixed terminal is fixed through the bottom surface of the case, and a second fixed terminal is provided on the bottom surface of the case, and these first,
In the overload protection device, the second fixed terminal portion is connected in series to the motor winding via the connection portion,
An overload protection device characterized in that a phase means is provided at a connection portion between the fixed terminal and the second fixed terminal. 2. In the product described in claim 1, the second fixed terminal is a heater terminal, the connection between the heater terminal and the first fixed terminal is a heater wire, and a part of the heater wire is a thin wire. An overload protection device characterized by having a section. 3. In the item described in claim 1, a temperature phase is provided at the connection portion between the first fixed terminal and the second fixed terminal, and the fusing temperature of this temperature phase is set higher than the reversal operating temperature of the bimetal. An overload protection device characterized by: