JPS6235212B2 - - 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 provides a sub-thermal switch in parallel with a heater for heating a main thermal switch similar to the conventional one, so that the minimum operating current characteristics with respect to ambient temperature can be made as uniform as possible, or vice versa. The purpose is to provide a thermal switch whose characteristics can be freely changed, such as increasing the slope of the characteristic curve as much as possible. explain.

1 to 4 show a first embodiment of the present invention, in which a housing 1 has a heat insulating wall 2 and a main room 3.
It is divided into sub-room 4.

The center of the downward dish-shaped main bimetal 7 of the normally closed main thermal switch is fixed to the upper end of the adjustment screw 6 screwed into the screw hole 5 drilled in the center of the bottom plate of the main chamber 3 from below. ing.

A pair of first movable contacts 8, 8 are vertically provided on the lower surface of the protrusion at both diametrical ends of the main bimetal 7.

A first fixed contact 9 is fixedly installed directly below one of the movable contacts 8 on the bottom plate of the main chamber 3, and a first fixed contact 9 that is close to and parallel to the lower surface of the main bimetal 7 is provided on the lower surface of the first fixed contact 9. One end of the heater 10 is connected.

The other end of the first heater 10 is connected to one end of the first connecting plate 11, and one power receiving piece 12 penetrating the bottom plate of the main chamber 3 and hanging downward is connected to the lower end of the first connecting plate 11. A second heater 13 is installed at the other end of the first connecting plate 11 that bends and hangs over the heat insulating wall 2.
is connected at one end.

The other end of the second heater 13 is connected to a sub-bimetal 14 which is in the form of a horizontal plate in a normally open sub-thermal switch installed in the sub-chamber 4 and whose operating temperature is lower than that of the main bimetal 7, that is, whose opening/closing temperature is lower. A second movable contact 15 connected to the base end and fixed to the free end of the sub-bimetal 14 faces and is in close contact with the second fixed contact 10.

The second fixed contact 16 bends over the heat insulating wall 2 and crosses over the second connecting plate 17 fixed to the bottom plate of the main chamber 3.
is fixed to one end of the

A third fixed contact 18 facing the other first movable contact 8 is fixedly installed on the upper surface of the other end of the second connecting plate 17, and a third fixed contact 18 that extends downwardly through the bottom plate of the main chamber 3 is also provided on the lower surface of the other end. The other power receiving piece 12 is connected in series.

When the main bimetal 7 is at a low temperature, the movable contacts 8, 8 and the fixed contacts 9, 18, which face each other, are in close contact with each other, and when the sub-bimetal 14 is at a low temperature, the second movable contact 15 and the second fixed contact 16 are spaced apart. .

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 raised by electrical heating caused by a current passing through itself, heating by the heater 10, and heat due to 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 are opened at the same time.

Further, the temperature of the sub-bimetal 14 is raised by its own current heating, heating by the heater 13, and heat from the ambient temperature, and when the sub-bimetal 14 reaches a temperature lower than the set temperature of the main bimetal 7, the movable contact 15 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 10 with respect to the ambient temperature. In other words, this diagonal line m indicates the main thermal temperature 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 14 and the second heater 13 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, assuming that the movable contact 15 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, t ₁ is the temperature of the sub-bimetal 14 when the movable contact 15 of the characteristic conversion section opens when the temperature falls, and t ₂ is the temperature of the sub-bimetal 14 when the movable contact 15 closes when the temperature rises. , t ₃ is the temperature of the main bimetal 7 when the movable contact 8 of the main thermal switch closes when the temperature falls, and t ₄ is the temperature of the main bimetal 7 when the movable contact 8 opens when the temperature rises.
temperature is shown respectively.

Furthermore, from this figure, it can be seen that when the ambient temperature is t ₄ °C or higher, the _eight movable contacts are opened by the main bimetal 7 even if no current i ² flows through the refrigerator. When using for example, the temperature is set much higher than room temperature, so in reality,
The ambient temperature never 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, 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 19 and a main switch 20
are connected in series to the power supply terminals 12, 12, and the main switch 20 is closed.

Since the characteristic converter is open until the ambient temperature of the characteristic converter rises to t ₂ °C, the controlled circuit 1
All current passing through 9 passes through main bimetal 7 and heater 10.

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 19 is divided between the heater 10 and the characteristic converter.
The amount of heating of the main bimetal 7 decreases, and the amount of heat generated by the main bimetal 7 decreases accordingly. In order to operate the main bimetal 7 and move the movable contact 8 in this state,
Since it is necessary to flow a larger current to the controlled circuit 19 by the amount of the heating amount of the heater 10 reduced, that is, by the amount of current shunted to the characteristic conversion section, the minimum operating current characteristic of the thermal switch of the present invention is indicated by the diagonal line m.
Moving upwards on the diagonal line n, A ₂ →B ₂ →B ₃ ...
...→It becomes like 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 12 , 12 . That is, the movable contact 8 opens.

With all movable contacts 8 and 15 closed,
If the ambient temperature drops from the high temperature side to t ₂ °C,
Since the auxiliary bimetal 14 is heated by the electrical heating and the heater 13, the movable contact 15 does not open yet at this point, and the movable contact 15 does not open until the ambient temperature drops to _t1 °C. 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, and becomes B ₂ →B ₁ .

When the ambient temperature reaches t ₁ °C and the movable contact 15 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 ₂ →A ₁ →A ₂ .

As described above, the minimum operating current characteristics of the thermal switch of the present invention are 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 10 and the second heater 13.

FIG. 5 shows a second embodiment of the present invention.
In place of the normally open auxiliary bimetal 14 in the first embodiment, a normally closed auxiliary bimetal 22 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, the minimum operating current characteristics with respect to the ambient temperature can be made as uniform as possible by providing the sub thermal switch in parallel with the heater for heating the main thermal switch, similar to the conventional one. It is meaningful to be able to freely change the characteristics so as to increase the slope of the characteristic curve or, on the contrary, to increase 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...
... Subchamber, 5 ... Screw hole, 6 ... Adjustment screw, 7 ... Main bimetal, 8 ... Movable contact, 9 ... Fixed contact,
10... Heater, 11... Connection plate, 12... Power receiving piece, 13... Heater, 14... Sub-bimetal, 15... Movable contact, 16... Fixed contact, 17
... Connection plate, 18 ... Fixed contact, 19 ... Controlled circuit, 20 ... Main switch, 21 ... Power terminal, 22 ... Sub-bimetal, m, n ... Diagonal lines.

Claims (1)

[Scope of Claims] 1. In a main thermal switch formed by connecting a bimetal and a heater in series, a sub-thermal switch for characteristic conversion whose operating temperature is lower than that of the bimetal is connected in series and in parallel with the heater. A thermal switch characterized in that the temperature characteristics of the main thermal switch can be changed by connecting it in the following manner. 2 A main thermal switch consisting of a bimetal and a heater connected in series is provided in the main chamber, and a characteristic conversion whose operating temperature is lower than that of the bimetal of the main thermal switch is installed in an auxiliary chamber thermally isolated from the main chamber. The temperature characteristics of the main thermal switch are converted by connecting the sub-thermal switch in series to the main thermal switch and in parallel with the heater. Thermal switch.