JPS63272314A - Switch apparatus for electric heater - 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] [Industrial Application Field] The present invention relates to a switch for opening and closing the power supply of a cooking device that uses an electric heater, such as a rice cooker that cooks by placing a pot on a heater. Regarding equipment. In particular, it relates to a cooker equipped with a temperature sensing element for detecting the temperature of the cooker itself and turning on/off the power supply.

[Description of prior art]

Conventionally, nine types of switch devices of this type have been provided, one example of which will be described with reference to FIGS. 4 and 5.

In this device, a temperature-sensitive magnetic body 1 having a single Curie point corresponding to the temperature to be detected is fixed to a heat receiving plate 2, and this temperature-sensitive magnetic body 1 is fixed to a heat receiving plate 2.
To do this, a permanent magnet 3 having a Curie point sufficiently higher than the temperature to be detected is fixed via a dish-shaped yoke 6 to a movable plate 5 which is biased away from the temperature-sensitive magnetic body 1 by an inner spring 4. They are facing each other. 7 is a non-magnetic thin plate for impact buffering.

These are the positions where the permanent magnet 3 attracts the temperature-sensitive magnetic body 1 when the temperature of the heat-sensitive body 11 is lower than the temperature of the temperature-sensitive magnetic body 1, that is, when the temperature-sensitive magnetic body 1 is a ferromagnetic material. Niashi, when the temperature rises.

That is, when the temperature-sensitive magnetic body 1 becomes a paramagnetic body, the permanent magnet 3 is separated from the temperature-sensitive magnetic body 1 by the biasing force of the inner spring 4 and is displaced to a predetermined position together with the movable plate 5. Therefore, the biasing force of the inner spring 4 is set to be smaller than the attractive force when the temperature-sensitive magnetic body 1 is a ferromagnetic material and is attracted to the permanent magnet 3.

Further, an operating rod 8 is connected to the movable plate 5, and the positional displacement of the movable plate 5 is transmitted to the outside of the case 9, so that temperature changes of the heated object can be detected by the positional displacement of the operating rod 8. . Such a switch device is used, for example, as a thermostat for an automatic rice cooker, and in this case, it can be used to cut off the power or stop the gas supply via a lever (not shown) connected to the lower end of the operating rod 8. It is structured to

In addition, this device has a mechanism for detecting the presence or absence of the object to be heated (inner pot) using a connecting lever 81, and this mechanism will be explained with reference to Figure 5 and Figures 3 (a) and (b). do.

Before heating (or when the temperature-sensitive magnetic material 1 is a ferromagnetic material), when the K inner pot is mounted (indicated by the solid line), the biasing force F12m of the outer spring 12 is weaker than the weight F85b of the inner pot (as shown). The movable part is stationary at the position shown in FIG. Here, by returning the movable plate 5 to the temperature-sensitive magnetic body 1 side via a lever 81 (see Fig. 3) connected to the lower part of the operating rod 8, the temperature-sensitive magnetic body 1 and the permanent magnet 3 are attracted to each other as shown in the figure. In this state, the power cutoff switch (fixed to the bottom of the cooker) (not shown) located at the bottom of the cooker is closed, and the heater 84 can be energized. Next, when the inner pot is removed from above the heater, the movable portion is raised by the biasing force F12a of the outer spring 12 until it overlaps the lever and the bottom surface of the outer case 13 (as shown by the dashed line). Here outer spring 12
The biasing force F12b is larger than the attractive force F1a between the temperature-sensitive magnetic body 1 and the permanent magnet 3 (F12b > F1a
) *The permanent magnet 3 separates from the temperature-sensitive magnetic body 1 via the biasing force F4a of the inner spring 4 and becomes the state shown in the dotted line in the figure.
By opening the switch 82 and cutting off the power to the heater 84, it is possible to detect the presence or absence of the heated object.

[Problem that the invention seeks to solve]

As mentioned earlier, the detection state (signal) of this switch device is determined by the interrelationship among the key temperature of the temperature-sensitive magnetic body 1, the attraction force (LA flux density) of the permanent magnet 3, and the biasing force of the inner spring 4. It's going to be successful.

Considering the variations in the characteristics of each device, there is a tendency for the operating temperature of the entire device to vary widely, which is undesirable in terms of design and manufacturing.

In addition, in order to detect the presence or absence of the inner pot, the biasing force F12a of the outer spring must be smaller than the own weight F85 of the inner pot 83, and the attractive force F1a between the temperature-sensitive magnetic body 1 and the permanent magnet 3
must be smaller than the above F12a, and must be sufficiently larger than the lever's own weight F81. In other words, eF1a is + F81 > F12a > F1a >
Must be within the relationship of Fal, approximately 150 in practical terms.
Must be between 250 gr and 250 gr. Furthermore, as mentioned above, the attractive force F1a also affects the operating temperature, so it is necessary to minimize variations in the magnetic density of the permanent magnets 3 and variations in the biasing force of the inner spring 4, so each component must be managed in a certain way. There is a problem in that it becomes necessary to check the condition or check the entire quantity, which significantly increases the cost.

Furthermore, as shown in FIG. 5, this device requires a large number of parts and mechanisms, resulting in a problem of high cost.

[Means for solving problems]

The present invention has been made in view of the above problems, and uses a coil spring made of a shape memory alloy in place of the temperature-sensitive magnetic material and permanent magnet as the temperature-sensing element used in the above-mentioned conventional switch device. This is what I used. More specifically,
A movable plate that can slide vertically is provided in a case made of a heat sensitive body, and a coil spring made of a shape memory alloy is interposed between the upper surface of the case and the movable plate to bias the movable plate downward. The convex portion provided on the inner wall of the case near the bottom of the case and the elastic peripheral edge of the movable plate are brought into frictional engagement, and the entire case is supported so as to be movable up and down within the case fixed to the heating element by means of a sling. .

One end is fixed to a movable plate, and the other end protrudes from a fixed case and has an operating rod connected to an on/off switch. Utilizing the property of this shape memory alloy to have a specific shape at a certain temperature, it has the same function as conventional temperature-sensitive magnetic materials and magnets, that is, it has two different functions on the movable plate at low temperatures and high temperatures. The opening switch is opened and closed by opening and closing the switch.

〔Example〕

As shown in FIG. 1, the heat sensitive body 11 (movable part) is.

Cover made of material with good thermal conductivity3. It is formed of a case 9, inside which a movable plate 5 and an operating rod 8 are connected to the lower part thereof, and between the cover 3 and the movable plate 5, a shape memory alloy 31 in the form of a bidirectional coil spring is connected to the movable plate. 5 is attached so as to bias it in a direction away from the cover. Further, the heat sensitive body 11 (movable part) is supported by a spring 12 in a fixed case 13 that is fixed to the side surface of the heater 84.

Next, the operation of this switch device will be explained.

Bidirectional coiled spring-like shape memory alloys generally have a transformation mechanism, changing their shape at a certain arbitrary temperature,
It is also known that the shape recovers as the temperature decreases, and that the shape changes rapidly near the operating temperature. Here, as shown in Figure 2, there may be a biasing force of F51a at low temperature + F31b at high temperature (operating temperature).

First, when the inner pot 83 is mounted on the heater 84 at room temperature, as shown in FIG. Because of this, it is stationary at the position shown in the figure,
The movable plate 5 has a biasing force F5ja of the shape memory alloy in the case 9.
Since the frictional force F5a between the protrusion 21 and the side surface of the movable plate 5 is smaller than the friction force F5a, the movable plate 59 is attached to the lower part of the lever 81 by the lever 81 connected via the operating rod 8. By pressing the power cutoff (opening/closing) switch 82, the switch 82 is in an open state.

Next, as already shown in FIG. 3, by pushing the lever 81 from the outside, the movable plate 5 is raised to a position where the protrusion 21 of the inner case 9 and the recess 22 on the side surface of the movable plate 5 are combined. Therefore, the lever 81 rises and separates from the switch 82, and the switch 82 becomes closed and starts energizing the heater 84.

If the inner pot 83 is removed from above the heater 84, the third
As shown in Figure d, the biasing force F12a of the outer spring 12 is
As a result, the movable portion 11 is raised until it comes into contact with the lever 81 and the bottom surface of the inner case 9. However, the outer spring 1
Since the biasing force F12b of No. 2 is larger than the frictional force F5a between the protrusion 21 of the inner case 9 and the recess 22 of the movable plate 5, the recess 22 of the movable plate 5 is.

The movable body 11 rises until it is separated from the protrusion 21 and reaches the state shown in FIG. 3e, and the movable part 5 descends. Therefore, the state shown in FIG. 3e is reached, the switch 82 is opened via the lever 81, and the power supply to the heater 84 is cut off. In this way, the presence or absence of the inner pot is detected and the heater 8 is automatically
Controls energization to 4.

In addition, when there is an inner pot 83 and the heater 84 is energized and the temperature inside the pot 83 rises to near the detection temperature, the shape memory alloy has a biasing force F31b and I F51b
Since this is larger than the frictional force F5a of the recess 22, the recess 22 of the movable plate 5 begins to separate from the protrusion 21, and as the movable plate 5 descends, the switch 82 is opened by the lever 81 via the operating rod 8, and the heater is turned off. 84 is cut off. (As shown in Figure 3C) From the above, the dead weight of the inner pot 83 is F81. Let Fal be the weight of the lever 81, etc.

F81 > Fl 2b > F5a > Fal-(
1) and F31b > F5a > Fsl ...
・・・・・・・・・・・・The mechanism design must satisfy the relationship (2), but in equation (1), the biasing force (relative to the biasing force of the mechanism for detecting the presence or absence of the inner pot) There are no factors that cause variations in temperature detection, and everything is left to the mechanism design. Further, in equation (2), the urging force (relationship of urging force that determines the operating temperature) is the urging force F51a + F51b of the shape memory alloy, and it is easy to establish the relationship of equation (1). In other words, the temperature detection function and the function of determining the presence or absence of the inner pot can be designed independently and easily.

〔effect〕

As described above, according to the present invention, the number of parts is reduced and the cost is reduced by using a shape memory alloy for the temperature detection element, compared to the conventional switch device that combines a temperature-sensitive magnetic material and a permanent magnet. It is possible to provide a switch device that can automatically detect the presence or absence of an inner pot that is independent of the temperature detection function.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a switch device according to the present invention. FIG. 2 is an exploded perspective view of a switch device according to the present invention. FIG. Relationship diagram FIG. 4 is a longitudinal sectional view of a conventional switch device. FIG. 5 is a diagram showing the operating position relationship of a conventional switch device. In the figure, 1 = temperature-sensitive magnetic material, 2: lid, 3: cover. 4: Inner sedge ring, 5: Movable plate, 8: Operating rod, 9 Ni case, 11: Heat sensitive body (movable part), 12 Ni spring, 13
: Fixed case, 21: Protrusion, 22: Recess (elastic periphery), 31: Shape memory alloy (coil spring), 81 Nilever, 82: Open/close switch, 83: Inner pot, 84: Heater. Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A movable body supported by a fixed case fixed to the heater by placing the object to be heated and biased upwardly by a spring so as to be able to move vertically is displaced against the biasing force. The presence or absence of the object to be heated is detected by a detection mechanism provided within the movable body, and the temperature of the object to be heated is detected by a temperature sensing element provided within the movable body, and the case is fixed. In a switch device for an electric heating device that opens and closes energization to a heater, the movable body includes a case with a heat sensitive element as a cover, a movable plate that slides in the case toward the cover, and a combination of the cover and the movable plate. The movable plate includes a coil spring that is interposed between the coil springs and biases the movable plate in a direction away from the cover, and a convex portion that is provided on the inner wall of the case and that frictionally engages the peripheral elastic portion of the movable plate near the bottom of the case. , the detection mechanism comprises an operating rod having one end fixed to the movable plate and the other end protruding from the fixed case and connected to an open/close switch, and the temperature sensing element is a coil spring made of a shape memory alloy. A switch device for an electric heating device characterized by the following. 2. The biasing force of the coil spring made of the shape memory alloy at room temperature is F_3_1_a, and the biasing force at high temperature is F_3.
_1_b, the biasing force of the spring is F_1_2_b,
When the weight of the object to be heated is F_8_3, the frictional resistance force of the convex portion is F_5_a, and the weight of the open/close switch lever connected to the operating rod is F_8_1, the following two formulas F
Claim 1 characterized in that the relationship satisfies _8_3>F_1_2_b>F_5_a>F_8_1 and F_3_1_b>F_5_a>F_3_1_a.
A switch device for an electric heating device as described in .