JPS6238871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermoelectromotive force element and a gas ignition safety device, and a first object of the invention is to provide a thermoelectromotive force element with a large thermoelectromotive force, long life, and high reliability; A second object of the invention is to provide a gas ignition safety device that includes the thermoelectromotive force element described above and has excellent performance.

As thermoelectromotive force elements, metal thermocouples such as copper-constantan, alumel-chromel, platinum-platinum rhodium, and semiconductor thermoelectric bodies such as Bi-Te and Bi-Sb have been known. By the way, the thermal electromotive force is only several +μV/℃ for metal thermocouples, and only about 100 to 300μV/℃ for semiconductor thermocouples.
In a stable temperature range (temperature range in which it does not melt or chemically oxidize), the electromotive force can only be on the order of 10 mV at most. Furthermore, among oxides, carbides, nitrides, and silicides that have high thermal stability, the thermoelectromotive rate is low, on the order of several μV/° C., except for oxides and silicides. The thermoelectromotive coefficient of silicides is ~200 μV/°C, and that of oxides is several hundred μV/°C, so these devices can be used to display gas pilots,
Alternatively, in order to issue an alarm or control a valve after detecting the extinguishment of a gas appliance, the electromotive force is small, so it is necessary to flow current through the circuit to increase the width.
In particular, when batteries are used as a power source, they have to be replaced frequently, making them impractical.

On the other hand, there have been two conventional methods for pilot flame display. One method involves inserting a platinum wire into the flame to act as a pilot flame, and guiding the light to the display using an optical fiber. In this case, the advantage is that there are no moving parts, but the disadvantages are that the light intensity is low and it is expensive. Another method is to insert a metal thermocouple such as chromel-constantan into the flame and use the electromotive force to operate a voltmeter. Although it is cheaper than the former, it has moving parts, the mounting position becomes a problem, and it is necessary to prevent moisture from entering the display part.

The main part of the present invention is composed of cuprous bromide alone or cuprous bromide plus cuprous iodide, and has a large specific region with a thermoelectrification rate of several mV/℃. , and provides a thermoelectromotive force element that can arbitrarily change the temperature transferred to its specific region and the melting point of its essential parts,
Furthermore, by providing a gas ignition safety device that includes the thermoelectromotive force element as a main part, the present invention attempts to eliminate the above-mentioned conventional drawbacks.Examples will be described below with reference to the drawings.

First, the structure of a thermoelectromotive force element, which is a first embodiment of the present invention, will be explained with reference to FIG. In the figure, 1 shows cuprous bromide (CuBr) and cuprous iodide (Cul) with a purity of 99.5% or higher heated in nitrogen or rare gas to near the melting point and treated until free halogen is eliminated. crush things,
The thermoelectromotive element body is molded using CuBr alone or a mixture of CuBr and Cu. 2 and 2' are thin layers of graphite molded on both sides of the element body 1 integrally with the body. This thin layer was made of graphite because CuBr and Cul are P-type semiconductors, and graphite is excellent as a material that does not create a potential barrier at the contact area, is thermally stable, and is inexpensive. It is. 3 is one graphite thin layer 2
The high-temperature side electrode is placed in contact with the container, and here it also functions as a container. The high-temperature side electrode 3 is made of a metal material that has excellent corrosion resistance at high temperatures because a protrusion 3' protruding from one end face enters the flame. Specifically, stainless steel containing 16% or more of chromium is suitable as it meets the above conditions. The open end of the high-temperature side electrode 3 is bent and presses the copper cap 4 through an insulating ring 5. 6 is a high temperature side lead connected to the high temperature side electrode 3 by spot welding. 7 is a lead on the low temperature side and is welded to the copper cap 4 with solder 8. Note that the portion of the high temperature side electrode 3 near the graphite thin layer 2, including the graphite thin layer 2 and the protrusions 3', constitutes the high temperature side electrode in a broad sense, while the graphite thin layer 2', the copper cap 4, the solder 8, etc. also constitutes a low temperature side electrode in a broad sense.

Next, the characteristics of the thermoelectromotive force element having the following configuration will be explained. FIG. 2a shows the state of thermoelectromotive force generation with respect to the temperature difference between the high-temperature electrode and the low-temperature electrode when the high-temperature electrode is heated. In the figure, curve A is a molded product made of CuBr alone, curve B is a product molded with a mixture of 95% CuBr and 5% Cul, and curve C is a product molded with a mixture of 90% CuBr and 10% CuBr. The main body of the samples used for this measurement had a diameter of 7.0 mmφ and a length of 15 mm.
mm, and the thickness of the graphite layer is 0.5 mm. The high temperature side electrode has a truncated conical shape with an inner diameter of 7.0 mm at the tip and 8.0 mm at the open end. The temperature of the low-temperature electrode is indicated by a broken line t in FIG. 1a. With CuBr alone, the electromotive force suddenly rises when the temperature difference is around 120℃, but when the temperature difference is around 200℃, the thermoelectromotive force reaches about 700mV and increases even if the temperature difference is increased beyond that. is small. 310 for CuBr95%
A rapid increase occurs with a temperature difference of ℃, and in the case of CuBr90%, a rise in thermoelectromotive force occurs with a temperature difference of 360℃. When the temperature of each high-temperature side electrode was heated to a temperature equivalent to the melting point (described later) of the material forming the main body, the thermoelectromotive force reached 750 mV.

FIG. 1b shows the temperature characteristics of conductivity measured for the three types of samples. This electrical conductivity substantially corresponds to the electrical conductivity of the element main body. Note that each curve in the figure is given the same reference numeral as in FIG. 1a to correspond to each curve.

Now, as can be seen from the temperature characteristics shown in Figure 1b, the rapid rise in thermoelectromotive force in Figure 1a occurs at a temperature around which conduction reaches its characteristic region, and the thermoelectromotive force is It was about 5 mV/°C.
Furthermore, the decrease in thermal electromotive force observed in the case of CuBr alone occurs in the temperature range where ionic conduction becomes dominant. Highly accurate temperature detection becomes possible by utilizing the region where the thermoelectromotive force rapidly increases. When trying to control temperature by obtaining a constant thermoelectromotive force, as is clear from Figure 2a, CuBr
For example, when CuBr is added, the temperature of the high-temperature side electrode where a thermoelectromotive force of 500 mV can be obtained is 250 °C when CuBr is used alone, and 470 °C when CuBr is 90% and Cul is 10%.
The temperature to be controlled can be increased, such as ℃.

Next, Figure 3 shows the change in melting point when Cul is added to CuBr. As is clear from the figure, the melting point increases by adding Cul. When a thermoelectromotive force element is used as a pilot flame display, it is quite possible that the temperature of the element body near the high-temperature side electrode reaches 500°C.
In such a case, if the element body is made of CuBr alone, there is a concern that part of the body will melt, but if the body is made of a material containing 5 to 10% Cu, such concerns can be avoided. is wiped away. Adding Cul to CuBr slows down its own response speed, but when the high-temperature side electrode is placed in a high temperature and detects the temperature, such as when used for a pilot flame display, the main body near the high-temperature side electrode The rate of temperature rise in The response delay becomes negligible. On the other hand, when used to detect abnormalities such as extinguishing a gas stove, CuBr alone is used because the amount of heat per unit volume of the stove flame is lower than that of the pilot flame, and the detection temperature range is low. By using a structure with a main body part, the main body part itself can have a faster response.

Next, we conducted an experiment to investigate the effect of heat dissipation on the thermoelectromotive force characteristics on the low-temperature side of the main body, and will discuss this.

First, as shown in Figure 4 a, CuBr95%/Cul5%
A hot plate 10 with a built-in heater 9 is brought into contact with the upper surface of the carbon thin layer 2 provided on one side of the element body 1 made by molding a mixture of A heat dissipation plate 11 (made of a copper plate with a diameter of 10 cm and a thickness of 2 cm) is brought into contact with the lower surface of the carbon thin layer 2' provided on the other side, and a low temperature side lead 7 is connected to the side surface to improve heat dissipation on the low temperature side. An excellent sample was prepared.
In the figure, 12 and 12' are thermocouples provided to measure the temperature in the thin carbon layers 2 and 2'.

In addition, as shown in FIG. 4b, sample 2 was prepared, which included a main body 1 molded from a mixture having the same composition as in a. Most of the structure is the same as in FIG. However, in this case, the copper cap 4 forming the low-temperature side electrode is located somewhat deeper than the opening of the container (the high-temperature side electrode 3 also serves as this, as in the case in Figure 1); The section is sealed with a glass hermetic lid 14 having a terminal 13 in the center. And copper cap 4 and terminal 13
are electrically and thermally connected by a compression spring 15.

With this structure, heat radiation from the low-temperature side electrode made of the copper cap 4 or the like to the outside air is suppressed. The thermocouple 11 is provided to measure the temperature of the surface of the high temperature side electrode 3 on which the protrusion 3' is provided, and the other thermocouple 12 is provided to measure the temperature of the terminal 13.

Further, as sample C, the same one as shown in FIG. 1 was prepared. The material composition of the body 1 is the same as in FIGS. 4a, b. The thermocouple was placed in the same state as in FIG. 4b.

Now, for each of the three types of samples A, B, and C prepared as described above, the high-temperature side electrode was heated, and the thermoelectromotive force and temperature of the low-temperature side electrode at that time were measured. The results are shown in FIG. Here, the solid line in the figure shows the thermoelectromotive force, and the broken line shows the temperature of the low temperature side electrode.
Further, the symbols attached to each curve correspond to the above-mentioned samples.
As is clear from the figure, in the case of sample RO, which has a structure that suppresses heat dissipation from the low-temperature side electrode, the temperature of the low-temperature side electrode is naturally higher than the other two; There is no sudden rise in thermoelectromotive force as seen in A and C. From this, it is understood that it is necessary to have a structure that allows sufficient heat dissipation at the low temperature side electrode. As shown in the figure, there is almost no difference between sample C and sample A. This shows that the structure shown in FIG. 1 has the same effect on heat radiation from the low-temperature side electrode as the one provided with a heat sink like sample A. This kind of heat dissipation effect is achieved by copper cap 4 as shown in Figure 1.
This is because the solder 8 is applied over a wide area on the surface, and the solder 8 is also in contact with the outside air over a wide area. In order to dissipate heat from the low-temperature side electrode, the structure is not limited to that shown in FIG. 1, of course.

Next, FIG. 5 shows the results of a repeated life test of heating for 2 hours and leaving for 2 hours for each of the three types of samples A, B, and C. The symbols attached to each curve correspond to samples A, B, and C, respectively. As is clear from this figure, sample C stably maintains its excellent thermoelectric properties over a long period of time. Although sample A has a structure that allows for heat dissipation from the low-temperature side electrode, the reason why the thermoelectromotive force gradually decreases as shown by curve A in the figure is because the structure of the electrode part is temporary. This seems to be due to the fact that

Next, a gas ignition safety device which is a second embodiment of the present invention will be explained using FIG.

In the figure, 21 is a thermo-electromotive force element provided by the first invention, and 22 is a transistor whose base and emitter are connected to both terminals of the thermo-electromotive force element 21. 23 is a light emitting diode whose minus terminal is connected to the collector of the transistor 22, and the other end is connected to the minus terminal of the battery 24 via a variable resistor 25. The other terminal of the battery 24 is connected to the emitter of the transistor 22.

Next, the operation of this device will be described. The thermoelectromotive force element 21 is arranged so that the protrusion (corresponding to FIG. 1 3') protruding from the end face of the high temperature side electrode of the thermoelectromotive force element 21 is located in the flame of the pilot flame of the gas combustor.
When the pilot flame is not lit, no thermal electromotive force is generated between both terminals of the electromotive force element 21, and therefore, in this state, the transistor 22 is non-conductive and the light emitting diode 23 is not lit. When the pilot flame is lit and the protrusion of the high-temperature side electrode is heated, a thermoelectromotive force is generated and a current flows to the base of the transistor 22, so that the transistor 22 becomes conductive and the light emitting diode 23 lights up. When the pilot flame is extinguished, no base current flows and the light-emitting diode turns off as described above.

In the above configuration, the thermoelectromotive force element generates a large thermoelectromotive force when heated by the pilot flame, so
There is no need to increase the thermoelectromotive force to drive the transistor, so there are fewer parts that make up this device, and of course there is no need for a power source to increase the width, making the entire device extremely simple and inexpensive. can. Since the thermoelectromotive force element, which can be said to form the heart of this device, has excellent life characteristics, this device maintains its function stably for a long time. Furthermore, as the thermoelectromotive force suddenly rises, the light emitting diode suddenly increases in brightness, so the display can be easily seen from a distance. Furthermore, since the current flowing through the light emitting diode is regulated by the variable resistor and no current from the battery flows into the primary side of the transistor, power consumption is extremely low.

In the above embodiment, a light emitting diode was provided to display the light of the pilot flame, but instead of the light emitting diode, for example, a control relay may be provided, and its operation can light up an indicator light or sound a buzzer to warn the driver. You can do it like this. Furthermore, a solenoid valve may be provided to automatically supply and stop the gas. Of course, a light emitting diode and a control relay or solenoid valve may also be provided together. Control relays or solenoid valves, etc. are transistor collectors,
By configuring the device to operate when the emitter is disconnected, battery consumption can be kept low.

FIG. 8 shows a modification of the gas ignition safety device shown in FIG. Basically, it has the same configuration as shown in FIG. 7, but in this case, the thermoelectromotive element 21 is connected to a Darlington circuit composed of two transistors 22' and 22''. As in the case shown in the figure, the current flowing to the primary side of the transistor is suppressed, so battery consumption is extremely low.

Note that explanations of elements common to each drawing have been omitted.

As described above, the thermoelectromotive force element obtained by the first invention has a large thermoelectromotive force, and by mixing cuprous bromide and cuprous iodide in an appropriate ratio, It is possible to arbitrarily change the temperature in a specific region where thermoelectromotive force rises rapidly. Therefore, if you want to detect temperature accurately in a certain temperature range, or if you want to detect a larger thermoelectromotive force in a certain temperature range. It can be easily dealt with when trying to obtain.

In addition, with a simple structure that only suppresses the temperature rise of the low-temperature side electrode, it is possible to not only increase the temperature difference with the high-temperature side electrode and extract a larger thermoelectromotive force, but also to suppress the thermoelectromotive force over a long period of time with good reproducibility. It can be taken out and can be highly reliable.

On the other hand, the gas ignition safety device obtained by the second invention is equipped with the excellent performance of the thermoelectromotive force element, and can accurately detect gas ignition and extinguishment.
Furthermore, there is no need to increase the thermoelectromotive force of the above-mentioned elements to drive an indicator light or buzzer that warns when the gas is on or off, or to issue an automatic command to stop the gas supply, which simplifies the configuration of the device. It has many excellent advantages, such as being able to be made at low cost.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a thermoelectromotive force element according to an embodiment of the present invention, FIG. 2a is a curve diagram showing the thermoelectromotive force of the thermoelectromotive force element, and FIG. FIG. 3 is a curve diagram showing the temperature characteristics of the electrical conductivity of the material forming the main part, FIG. 3 is a curve chart showing the change in melting point with respect to the composition of the material forming the main part, and FIGS. 5 is a front view and a cross-sectional view of a sample made to examine the heat dissipation effect of the low-temperature side electrode that makes up the device. FIG. 5 is a curve diagram showing the thermoelectromotive force characteristics of the thermoelectromotive force element and the sample. A curve diagram showing the life characteristics of the above thermoelectromotive force element and the above sample, Fig. 7 is a circuit diagram of a gas ignition safety device which is a second embodiment of the present invention, and Fig. 8 is a modification of the above gas ignition safety device. It is a circuit diagram. 1...Element body, 2, 2'...Carbon thin layer,
3...High temperature side electrode, 4...Copper cap, 6...High temperature side lead, 7...Low temperature side lead, 12, 12'
... Thermocouple, 21 ... Thermoelectromotive force element, 22,2
2', 22''...Transistor, 23...Light emitting diode, 24...Battery.

Claims (1)

[Scope of Claims] 1. A molded body containing cuprous bromide adjusted to be free of halogen, and a high-temperature side electrode and a low-temperature side electrode that are crimped to both sides of this molded body through graphite layers, respectively. A thermoelectromotive force element having 2. The thermoelectromotive element according to claim 1, wherein the molded body contains cuprous iodide adjusted to be free of halogen. 3. The high-temperature side electrode is integrated with the cylindrical body to form a container with one end open, and the end surface of the low-temperature side electrode housed in the container together with the molded body is connected to the open end of the container through a heat-resistant insulating ring made of ceramics. 2. The thermoelectromotive force element according to claim 1, further comprising a solder layer pressed by a bent portion formed in the insulating ring and bonded to the low-temperature side electrode on the inside of the insulating ring. 4. The thermoelectromotive element according to claim 1 or 3, wherein the high temperature electrode is made of stainless steel containing 16% or more of chromium. 5 Claim 1 in which the low temperature side electrode is made of copper
The thermoelectromotive force element according to item 1 or 3. 6 A molded body containing cuprous bromide adjusted to be free of halogen, a high-temperature side electrode provided on both sides of this molded body through graphite layers, and located in a high-temperature atmosphere, and a low-temperature atmosphere. A thermoelectromotive force element having a low-temperature side electrode located at the input circuit of the transistor is inserted into the input circuit of the transistor, and at least one of a display device that indicates whether the gas is turned on or off and a control device that controls the supply of the gas is inserted into the output circuit of the transistor. A gas ignition safety device characterized by being inserted. 7. The gas ignition safety device according to claim 6, wherein the molded body contains cuprous iodide adjusted to be free of halogen. 8. The gas ignition safety device according to claim 6, which uses a light emitting diode as the display device.