JPH0330773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a thermocouple device for flame detection used in safety devices of gas appliances and the like.

<Conventional technology and its problems> During combustion, the thermoelectromotive force of the thermocouple keeps the solenoid valve open, and when the flame goes out and the thermoelectromotive force decreases, the solenoid valve closes to prevent raw gas from flowing out. Safety devices for gas appliances are well known. In this case, the thermocouple is placed near the burner so that it can detect the occurrence of a flame, but it must be kept away from spilled broth. Therefore, for example,
Like the burner described in Publication No. 120334,
Attempts have been made to use a burner with a sub-combustion chamber and to house not only the spark plug but also the thermocouple in the sub-combustion chamber.

<Problems to be solved by the invention> Generally, the temperature of the burner does not drop immediately after the flame is extinguished, so if a thermocouple is placed in the sub-combustion chamber, the flame will be extinguished and raw gas will continue to come out. Even in the event of an abnormal situation, the thermoelectromotive force of the thermocouple does not come down easily, causing a problem that the operation of the safety device is delayed.

The present invention has focused on these problems, and has been made with the object of obtaining a flame detection thermocouple device that can detect a decrease in temperature with high sensitivity and is suitable for use in the above-mentioned applications. .

<Means for Solving the Problems> In order to achieve the above object, the flame detection thermocouple device of the present invention has a first conductor, a second conductor, a third conductor, and a fourth conductor connected in series. to make the connection point between the second conductor and the third conductor a hot junction placed near the flame to be detected, and the connection point between the first conductor and the second conductor. and a connection point between the third conductor and the fourth conductor is arranged at a position away from the flame, and heat generation between the first conductor and the second conductor and between the third conductor and the fourth conductor is arranged. The electric power is configured so that the polarity is opposite to the thermoelectromotive force between the second conductor and the third conductor, and the sum of the thermoelectromotive force at each connection point quickly decreases when the flame is extinguished. .

<Function> FIG. 1 is an explanatory diagram of the principle of the thermocouple device of the present invention, where 1 is a first conductor, 2 is a second conductor, and 3 is a third conductor.
, 4 is a fourth conductor, and 5 is a hot junction.

As is well known, a thermocouple is constructed by combining two conductors with a remarkable Seebeck effect, and its thermoelectromotive force is a constant ( Seebeck coefficient). Therefore, in the thermocouple device of the present invention configured as described above, the Seebeck coefficient between the first conductor 1 and the second conductor 2 is α ₁₂ ,
The Seebeck coefficient between the conductor 2 and the third conductor 3 is α ₂₃ , the Seebeck coefficient between the third conductor 3 and the fourth conductor 4 is α ₃₄ , and the temperature of the hot junction 5 is α 23 .
T ₁ , the temperature at each connection point of the first conductor 1 and the second conductor 2 and the third conductor 3 and the fourth conductor 4, respectively.
When T ₂ is the temperature at the other end of the first conductor 1 and the fourth conductor ₄ , the thermoelectromotive force E is approximately expressed by the following equation.

E = α ₂₃ (T ₁ − T ₃ ) + (α ₁₂ + α ₃₄ ) (T ₂ − T ₃ )... Generally, T ₁ > T ₂ > T ₃ , so (T ₁ − T ₃ ) and (T ₂ −T ₃ ) is positive, and the thermoelectromotive force between the first conductor and the second conductor and between the third conductor and the fourth conductor is equal to the thermoelectromotive force between the second conductor and the third conductor. Setting the polarity to be opposite to the power means making α ₁₂ and α ₃₄ , which are the coefficients of the second term on the right side of this equation, negative. Therefore, the first term on the right side of the equation is positive and the second term is negative, and the temperature of the hot junction 5 has fallen to some extent from the steady state T ₁ ≫ T _{2 .}
When T ₂ is reached, if the temperature of each part and each coefficient have an appropriate relationship, E=α ₂₃ (T ₁ − T ₃ ) + (α ₁₂ + α ₃₄ ) (T ₂ − T ₃ )≦0. It becomes possible to be satisfied. In other words, even if the temperature of the hot junction 5 is relatively high, the overall thermoelectromotive force can be rapidly reduced, or depending on the conditions, it can be made negative, and a decrease in the temperature of the hot junction 5 can be quickly detected. It can be done.

<Example> Next, the illustrated example will be specifically described. The thermocouple device of the present invention was developed with the direct purpose of incorporating it into the sub-combustion chamber of the burner of a gas appliance, and this example also shows an example of this. The thermocouple device is not limited to use in gas appliances, and can of course be used to detect flames in burners for other uses.

In Figures 2 and 3, 11 is the body 11.
A burner 12 consisting of a and a burner cap 11b.
13 is a flame port formed on the circumferential surface of the burner 11, and 13 is an auxiliary combustion chamber provided at one location on the circumferential surface of the burner 11.
14 is a gas flow path to the sub-combustion chamber, 15 is a burner 11
It is a mixing pipe that supplies mixed gas to the burner 11.
The mixing tube 15 and the mixing tube 15 are appropriately fixed to the main body of the instrument by a support plate (not shown). 20 is attached to the burner 1 through a fixing fitting 21 with its tip facing the sub-combustion chamber 13.
1, in which a thermocouple device 22 according to the present invention and a spark plug 23 are held together by an insulator 24.

The thermocouple device 22 includes a first conductor 1, a second conductor 2, a third conductor 3, and a fourth conductor 4 in FIG.
Four types of conductors 22a, 22 respectively corresponding to
b, 22c, 22d, and conductors 22b and 22
The connection point with c becomes the hot junction 22e, and the sub-combustion chamber 1
3, and is heated by a gas flame supplied from the gas flow path 14, and lead wires 25 are connected to the conductors 22a and 22d, respectively. Further, the hot junction 22e has a thin and wide-area shape in order to increase heat receiving efficiency, secure necessary heat capacity, and reduce electrical resistance.

Now, for each of the above-mentioned conductors 22a to 22d, materials known for thermocouples can be used as appropriate, and four types of materials can be combined in consideration of the Seebeck coefficient. Two types of materials are used. That is, for example, conductor 2
Chromel is used for 2a and 22c, and conductors 22b and 2
The first conductor 22a and the third conductor 22c are made of the same material, and the second conductor 22b and the fourth conductor 22d are made of the same material other than the above, such as using alumel for the material 2d. has been done. Therefore, the operation explanatory diagram corresponding to FIG. 1 is as shown in FIG. 4, and in the above equation, α ₁₂ and α ₃₄ in the second term on the right side are replaced with (−α ₂₃ ), and E=α ₂₃ ( It can be expressed as T ₁ −T ₃ )−(α ₂₃ +α ₂₃ )(T ₂ −T ₃ )=α ₂₃ (T ₁ −2T ₂ +T ₃ )...

Generally, during normal combustion, T ₁ is a high temperature close to the flame temperature, so T ₁ ≫ T ₂ ≧ T ₃ , and the value in parentheses on the right side of the equation is positive, and the thermoelectromotive force E is a relatively large positive value. Thus, the electromagnetic valve of the safety device is sufficiently energized and held in the open state.

Next, if an abnormal extinguishing situation occurs in which the raw gas does not stop even though the flame has been extinguished due to some abnormality, T ₁ will be lower than during combustion, but the Combustion chamber 13
There is a hot junction 22e inside, and the raw gas exiting from the gas flow path 14 is also continuously heated by the burner 11, so T ₁ decreases more slowly than when the thermocouple is placed outside the burner. Then, the difference between T ₁ and T ₂ decreases and becomes T ₁ > T ₂ , so the value in the parentheses on the right side of the equation is not necessarily a large positive value, and T ₁ −2T ₂ +T ₃ ≦0... ... becomes a state in which it can be easily established. This condition is determined only by the temperature of each part, for example, T ₁ = 280℃, T ₂ = 180℃, T ₃ = 60℃
If so, the formula becomes 280−2×180+60=−20, and in this case, the thermoelectromotive force E
passes through zero and becomes negative. In this way, when the thermoelectromotive force E becomes negative, it means that there is always a state where it becomes zero before that, and this makes it possible to operate the safety device quickly and reliably. It is.

Figures 5 and 6 are graphs showing an example of changes in temperature and thermoelectromotive force at each part. In Figure 6, A shows the thermoelectromotive force of this example, and B shows the thermoelectromotive force of the conventional thermocouple. As in the example, the thermoelectromotive force when stored in the auxiliary combustion chamber is shown. As shown in the figure, T ₁ rises rapidly after ignition, but T ₂ and T ₃ rise slowly due to heat conduction, and eventually reach a steady state. Although the thermal electromotive force at this time is smaller in the embodiment than in the conventional one, there is no problem if the specifications of the electromagnetic valve of the safety device are adjusted to this. In addition, since E≦0 is quickly established when extinguishing a fire, if the specifications of the mixing tube are adjusted to this, the adsorption time at the time of ignition can be made faster than when using a conventional thermocouple.

Next, when a fire is extinguished, the temperature of each part drops as shown in the diagram, and in the conventional system, a thermoelectromotive force approximately proportional to T ₁ is obtained, so the voltage does not easily drop to the point where the safety device operates. On the other hand, in the example, the electromotive force decreases rapidly, and in the example shown in this figure, it becomes zero when the temperature of each part reaches approximately T ₁ = 300°C, T ₂ = 185°C, and T ₃ = 70°C. After that, it becomes a small negative value. Therefore, the safety device operates quickly, and the continued release of raw gas for a long period of time is reliably prevented.

In this way, in this embodiment, it is possible to reliably detect an abnormal extinguishing state in which the flame is extinguished and raw gas is flowing out.
It can be stored in one sub-combustion chamber 13. Therefore, there is no need to use a particularly corrosion-resistant material as a measure against boiling water, and the overall structure can be simplified by making the electrical unit 20 integrated with the ignition plug, making it possible to reduce costs. . In addition, since the thermocouple device 22 is protected by the burner 11, it is possible to prevent accidents such as accidental damage when cleaning the device.Furthermore, since the thermoelectromotive force decreases quickly when extinguishing a fire, it is possible to prevent the solenoid valve from being damaged. The switching voltage can be lowered than before, and costs can be reduced by downsizing the solenoid valve.

<Effects of the Invention> As is clear from the description of the above embodiments, the present invention provides a first conductor, a second conductor, a third conductor,
A fourth conductor is connected in series to connect the second conductor and the third conductor.
A thermocouple is constructed in which the connection point of the conductors is a hot junction, and the thermoelectromotive force between the first conductor and the second conductor and between the third conductor and the fourth conductor is The polarity is opposite to the thermoelectromotive force between the conductors, and the temperature drop at the hot junction can be detected with high sensitivity. Therefore, it is possible to reliably detect the extinguishment of a flame even if it is placed in a place where the temperature does not easily drop when extinguishing, such as the sub-combustion chamber of a stove burner as in the embodiment, and flame detection in various burners is possible. This makes it possible to obtain a thermocouple device suitable for various purposes.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a side sectional view of the main part of an embodiment of the gas appliance, Fig. 3 is a partially cutaway front view of the same, and Fig. 4 is an explanatory diagram of the operation of the same. , FIG. 5, and FIG. 6 are graphs showing examples of changes in temperature and thermoelectromotive force at various parts, respectively. 1, 22a...first conductor, 2,22b...second conductor, 3,22c...third conductor, 4,22
d... Fourth conductor, 5, 22e... Hot junction, 22
...Thermocouple device.

Claims (1)

[Claims] 1 First conductor, second conductor, third conductor, fourth conductor
conductors are connected in series so that the connection point between the second conductor and the third conductor is a hot junction placed near the flame to be detected, and the connection point between the first conductor and the second conductor is connected in series.
The connection point with the conductor and the connection point between the third conductor and the fourth conductor are arranged at a position away from the flame, and between the first conductor and the second conductor and between the third conductor and the fourth conductor.
By making the thermoelectromotive force between the conductors have the opposite polarity to the thermoelectromotive force between the second conductor and the third conductor, the sum of the thermoelectromotive forces at each connection point is quickly added when the flame is extinguished. 1. A thermocouple device for flame detection, characterized in that the thermocouple device is configured such that the temperature decreases to .