JPS6244371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal switch that utilizes the temperature characteristics of bimetals and is used for automatic control and safety measures of refrigerators, air conditioners, or other electrical equipment.

For example, in this type of thermal switch used to prevent overload of compressors in refrigerators and air conditioners, it is desirable that the minimum operating current is always maintained at a constant value, unaffected by the ambient temperature. .

However, this type of conventional thermal switch has a problem in that the minimum operating current changes significantly due to changes in ambient temperature.

Conversely, when the ambient temperature is significantly lower than the set temperature and the heat dissipation effect of the windings is large, such as when it is desired to limit the temperature rise of the motor windings to below a predetermined set temperature. In some cases, it may be desirable to maintain the minimum operating current high and to increase the slope of the minimum operating current characteristic with respect to the ambient temperature so that the minimum operating current becomes lower as the ambient temperature approaches the set temperature.

The present invention makes it possible to make the minimum operating current characteristics with respect to ambient temperature as uniform as possible by providing a sub thermal switch in parallel with the main thermal switch similar to the conventional one. The purpose of this invention is to provide a thermal switch whose characteristics can be freely changed, such as by increasing the slope of the curve, and will be specifically explained below with reference to the attached drawings.

1 to 4 show a first embodiment of the present invention, in which a housing 1 is partitioned into a main chamber 3 and a sub-chamber 4 by a heat insulating wall 2. As shown in FIG.

At the upper end of an adjusting screw 6 screwed from below into a screw hole 5 drilled in the center of the bottom plate of the main chamber 3, there is a main bimetal 7 in the shape of a downward dish, which is made of a resistor whose temperature increases by heating with electricity. is fixed.

The protruding lower surface of one end of the main bimetal 7 has a first
A movable contact 8 is provided vertically, and a second movable contact 9 and a third movable contact 10 are also provided vertically on the lower surface of the bifurcated protrusion at the other end.

A first fixed contact 11 is fixedly installed directly below the first movable contact 8 on the bottom plate of the main chamber 8. On the lower surface of the first fixed contact 11, a main bimetal 7 is provided adjacent to the lower surface of the main bimetal 7. One end of a first heater 12 for auxiliary heating of the bimetal 7 is connected.

The other end of the first heater 12 is connected to one end of the first connecting plate 13, and one power receiving piece 14 penetrating the bottom plate of the main chamber 3 and hanging downward is connected to the lower end of the first connecting plate 13. A second heater 15 is installed at the other end of the first connecting plate 13 that bends over the heat insulating wall 2 and climbs over the heat insulating wall 2.
is connected at one end.

The other end of the second heater 15 is installed in the auxiliary chamber 4 and is made of a low-temperature antibody whose temperature increases by heating with electricity. A fourth movable contact 17 fixedly connected to the free end of the fourth movable contact 16 faces a second fixed contact 18 .

The second fixed contact 18 is a second fixed contact that is bent so as to overcome the heat insulating wall 2 and fixed to the bottom plate of the main chamber 3.
It is fixed to one end of the connecting plate 19.

A third fixed contact 20 facing the third movable contact 10 is fixedly provided on the upper surface of the other end of the second connecting plate 19 .

A fourth fixed contact 21 is fixedly installed directly below the second movable contact 9 on the bottom plate of the main chamber 3, and the other one penetrating the bottom plate of the main chamber 3 and hanging down is attached to the lower surface of the fourth fixed contact 21. Power receiving pieces 14 are provided in series.

When the main bimetal 7 is at a low temperature, the movable contacts 8, 9, 10 and the fixed contact 11, which face each other,
21 and 20 are in close contact with each other, and when the sub-bimetal 16 is at a low temperature, the fourth movable contact 17 and the second fixed contact 18 are separated.

In the above configuration, the movable contacts 9 and 10 and the fixed contacts 20 and 21 form a normally closed switching contact that is opened and closed by the main bimetal 7, and the switching contacts, the main bimetal 7, and the first heater 12 The series circuit forms the main thermal switch.

Furthermore, with the movable contact 17 and the fixed contact 18,
A normally open switching contact that is opened and closed by the sub-bimetal 16 is formed, and a series circuit of this switching contact, the sub-bimetal 16, and the second heater 15 forms a sub-thermal switch for characteristic conversion.

The operation of the thermal switch of the present invention having the above structure will be explained below with reference to FIGS. 4 and 6.

The temperature of the main bimetal 7 is increased by electrical heating caused by an electric current passing through itself, heating by the heater 12, and heat from the ambient temperature such as the atmosphere inside the chamber of a refrigerator, and when the main bimetal 7 reaches the set temperature. , the movable contacts 8, 9, and 10 open simultaneously.

Further, the temperature of the sub-bimetal 16 is raised by its own current heating, heating by the heater 15, and heat from the ambient temperature, and when the sub-bimetal 16 reaches a temperature lower than the set temperature of the main bimetal 7, the movable contact 17 is set to close.

In FIG. 6, the diagonal line m indicates the minimum operating current characteristic of only the main thermal switch constituted by the main bimetal 7 and the first heater 12 with respect to the ambient temperature. In other words, the diagonal line m indicates the main thermal switch when the ambient temperature is a certain temperature in a thermal switch with the same configuration as the conventional thermal switch in which the characteristic conversion section consisting of the sub-bimetal 16 and the second heater 15 has been removed. Indicates the minimum current value ⁱ² required for the switch to operate.

The diagonal line n indicates the minimum operating current characteristic with respect to the ambient temperature when it is assumed that the movable contact 17 is always closed in the configuration of the present invention in which a characteristic converter is added to the main thermal switch.

On the temperature axis, _t1 is the temperature of the sub-bimetal 16 when the movable contact 17 of the characteristic converter opens when the temperature falls, _t2 is the temperature of the sub-bimetal 16 when the movable contact 17 closes when the temperature rises, _t3 is the movable contacts 8, 9, 1 of the main thermal switch when the temperature decreases.
The temperature of the main bimetal 7 when 0 closes, and t ₄
indicate the temperature of the main bimetal 7 when the movable contacts 8, 9, and 10 open when the temperature rises.

Furthermore, from this figure, it can be seen that when the ambient temperature is t ₄ °C or higher, the main bimetal 7 opens the movable contacts 8, 9, and 10 even if no current i ₂ flows through the main bimetal 7, but this temperature t ₄ When used in a refrigerator or the like, the temperature is set much higher than room temperature, so the ambient temperature never actually reaches this temperature _t4 .

Points A ₀ , A ₁ , A ₂ , A ₃ , and X on the diagonal line m and points B ₀ , B ₁ , B ₂ , B ₃ , and X on the diagonal line n have a temperature of 0°C, t ₁ °C, respectively. These points correspond to t ₂ ℃, t ₃ ℃, and t ₄ ℃.

As shown in FIG. 4, the thermal switch of the present invention, a controlled circuit 22 and a main switch 23
are connected in series to the power supply terminals 24, 24, and the main switch 23 is closed.

Since the characteristic converter is open until the ambient temperature of the characteristic converter rises to t ₂ °C, the controlled circuit 2
All current passing through 2 passes through the main thermal switch.

Therefore, during this period, the thermal switch of the present invention is entirely controlled by the main thermal switch, and its minimum operating current characteristic is as shown by the diagonal line m in FIG.
It becomes like A ₀ →A ₁ →A ₂ .

When the ambient temperature reaches t ₂ °C, the characteristic converter closes and the current passing through the controlled circuit 22 is divided into the main bimetal 7 and the characteristic converter, so the amount of heat generated by the main bimetal 7 decreases. In this state, in order to operate the main bimetal 7 and open the movable contacts 8, 9, and 10, it is necessary to flow a larger current to the controlled circuit 22 by the amount shunted to the characteristic conversion section. The minimum operating current characteristic of the inventive thermal switch shifts to the diagonal line n above the diagonal line m, and is A ₂
→B ₂ →B ₃ ...→X.

Therefore, when the ambient temperature is t ₂ °C or higher, the operation is activated when a current higher than the diagonal line n flows between the power receiving pieces 14 , 14 . That is, movable contacts 8, 9, 10
opens.

If the ambient temperature drops from the high temperature side to t ₂ °C with all movable contacts 8, 9, 10, and 17 closed, the secondary bimetal 16 is heated by the current heating and heater 15, so at this point In this case, the movable contact 17 has not yet opened and the ambient temperature is t ₁ °C.
The movable contact 17 opens only after it has descended to this point. Therefore, the minimum operating current characteristic when the ambient temperature drops from t ₂ °C to t ₁ °C at this time passes along the diagonal line n,
B ₂ →B ₁ .

When the ambient temperature reaches t ₁ °C and the movable contact 17 opens, the thermal switch of the present invention returns to its initial state, and the minimum operating current characteristic shifts to the diagonal line m side,
B ₁ →A ₁ →A ₀ .

As mentioned above, the minimum operating current characteristic of the Marsal switch of the present invention is A ₀ →A ₁ →A ₂ →B ₂ →B ₃ →X→B ₃
→B ₂ →B ₁ →A ₁ →A ₀ , the characteristic includes a loop, and can be made more uniform overall than the conventional characteristic with the diagonal line m. That is, even if the ambient temperature increases, the minimum operating current can be maintained high, and the device can operate in response to overloads without being greatly affected by the ambient temperature.

The characteristics of the thermal switch of the present invention can be varied in various ways by adjusting the adjusting screw 6 and by changing the resistance values of the first heater 12 and the second heater 15.

FIG. 5 shows a second embodiment of the present invention.
In place of the normally open auxiliary bimetal 16 in the first embodiment, a normally closed auxiliary bimetal 25 is used. The other members are completely the same as those in the first embodiment, are given the same reference numerals in the drawings, and detailed explanations are omitted.

In the case of this second embodiment, the minimum operating current characteristics are:
B ₀ →B ₁ →B ₂ →A ₂ →A ₃ →X→A ₃ →A ₂ →A ₁ →B ₁ →B ₀
Therefore, contrary to the case of the first embodiment, the slope of the characteristic becomes large.

Utilizing such a characteristic of a steep slope, it can be effectively used as a thermal switch for maintaining the temperature rise of the winding portion of the motor below a set temperature.

As is clear from the above, according to the present invention, by providing a sub thermal switch in parallel with a main thermal switch similar to the conventional one, the minimum operating current characteristics with respect to ambient temperature can be made as uniform as possible, or On the contrary, it is meaningful to be able to freely change the characteristics, such as increasing the slope of the characteristic curve as much as possible.

[Brief explanation of the drawing]

1 is a plan view of the first embodiment of the thermal switch of the present invention with the top cover removed, FIG. 2 is a vertical sectional view taken along the line X--X in FIG. 1, and FIG. 3 is a - Y-line longitudinal cross-sectional view, FIG. 4 is the first embodiment of the present invention.
FIG. 5 is an equivalent circuit diagram of the second embodiment of the present invention, and FIG. 6 is a chart showing the minimum operating current characteristics of the thermal switch of the present invention. 1...Housing, 2...Insulating wall, 3...Main room, 4...Subroom,
7... Main bimetal, 9, 10, 20, 21... Opening/closing contact opened/closed by the main bimetal, 12,
15... Auxiliary heater, 16, 25... Sub-bimetal, 17, 18... Opening/closing contact opened/closed by the sub-bimetal.

Claims (1)

[Scope of Claims] 1. A main thermal switch formed by connecting in series a main bimetal whose temperature is raised by electrical heating and a switching contact which is opened and closed by the main bimetal, which is heated by electrical heating, and A secondary thermal switch for characteristic conversion, which is formed by connecting in series a secondary bimetal whose operating temperature is lower than that of the primary bimetal, and a switching contact opened and closed by the secondary bimetal, is connected in parallel to the primary bimetal, and is connected in series to open/close the switching contact of the primary thermal switch. A thermal switch characterized in that the temperature characteristics of the main thermal switch are changed by connecting it in series to the contacts. 2. The thermal switch according to claim 1, wherein the main thermal switch is provided with a heater for auxiliary heating of the main bimetal, which is connected in series with the main bimetal. 3. Claim 1 or 2, wherein the secondary thermal switch is provided with a heater for auxiliary heating of the secondary bimetal, which is connected in series with the secondary bimetal.
Thermal switch described in section. 4 A main thermal switch consisting of a main bimetal whose temperature is raised by electrical heating and a switching contact opened and closed by the main bimetal are connected in series in the main room, and is thermally isolated from the main room. A sub-thermal switch for characteristic conversion is provided in the sub-chamber, which is formed by connecting in series a sub-bimetal whose temperature is raised by electrical heating and whose operating temperature is lower than that of the main bimetal, and an opening/closing contact opened/closed by the sub-bimetal. A thermal switch characterized in that the temperature characteristics of the main thermal switch are changed by connecting the sub thermal switch in parallel to the main bimetal and in series with the opening/closing contact of the main thermal switch.