JPH08105624A - Exhaust air block detection device - Google Patents

Abstract

PURPOSE: To make it possible to stabilize electromotive force irrespective of related dimensions and protect from misjudgment during cold starting time by installing a thermal capacity body whose projection area in the vent hole direction is specific-sized to an opening area of a thermal capacity flow out vent hole to a hot junction of a thermocouple which generates electromotive force with exhaust gas heating. CONSTITUTION: A secondary thermocouple 1, which is an exhaust air block detection device, starts overflowing of exhaust air from a vent hole 3 installed to the side wall of a combustion chamber 16 when an exhaust air flow passage of a heat exchanger 29 is blocked with a combustion product and detects the overflowing exhaust gas and generates electromotive force. A hot junction support part, which forms the secondary thermocouple 11, is formed with two dissimilar metals of chromel and constantan respectively and a welded jointed part forms a hot junction. A cylinder-shaped thermal capacity body 4, whose projection area in the vent direction ranges from 1 to 1/3 against the opening area of the vent hole 3, is installed to the secondary thermocouple 11 so as to enclose the hot junction. Therefore, it is necessary to install a thermal capacity body 4 whose size is, preferably, 4mm in diameter and 5mm in length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust blockage detecting device, and more particularly to an exhaust blockage detecting device for detecting exhaust blockage based on an electromotive force level of a thermocouple.

[0002]

2. Description of the Related Art Conventionally, a through hole for letting out a part of exhaust gas is provided in a side wall of a combustion chamber, a hot junction of a thermocouple is exposed to this through hole, and an exhaust gas passage is blocked by a combustion product or the like. In this case, there is known an exhaust gas clogging detection device that generates an electromotive force in a thermocouple by exhaust gas flowing out from a through hole, detects a clogging tendency based on this electromotive force level, and stops combustion before incomplete combustion occurs. ing.

[0003]

However, in such an exhaust blockage detecting device, there is a problem in that the relative position between the thermocouple and the through hole must be manufactured with high accuracy. This is because the outflow amount of the exhaust gas flowing out from the through hole on the side wall of the combustion chamber is not uniform over the entire through hole and increases as the temperature increases above the opening, and the temperature of the exhaust gas also increases as the temperature increases above the opening. This is because the electromotive force characteristics of the thermocouple are likely to change when the positional relationship between the pair of hot junctions deviates from the proper position. This is also because the exhaust gas outflow distribution of the through holes is not uniform, and the heating area of the thermocouple due to the exhaust gas changes when the amount of contact of the thermocouple in the through holes changes. For example, as shown in FIG. 4, the exhaust blockage detection device disclosed in Japanese Utility Model Publication No. 4-24281 adjusts the amount of protrusion of the hot junction support portions 5 and 6 supporting the hot junction 2 from the side edge of the through hole 3. However, the advantage is that the electromotive force generated can be adjusted to an appropriate value by changing the heat receiving length of the hot junction support portions 5 and 6. However, on the contrary to this advantage, the generated electromotive force changes even if the positional relationship is slightly deviated. Further, when repairing a heat exchanger or the like, if the thermocouple 1 is detached from the combustion chamber 16 and then reassembled to move out of the proper relation position, there is a concern that the electromotive force characteristics may change.

Therefore, pay close attention to the production of the exhaust blockage detection device, and improve the processing accuracy of each part so that, for example, the position of the hot junction 2 of the thermocouple 1 is incorporated in the proper position of the through hole 3. However, it has been necessary to reduce variations in combined dimensions and manufacture within a delicate good range, and as a result, there is a problem in that it becomes expensive.

On the other hand, at the time of ignition (called cold start) in a state where the combustor is completely cold, there is a problem that the gas flow passage is extinguished due to an erroneous determination by the exhaust blockage detection device and the gas is likely to extinguish. . The reason for this is that the draft force of the combustion exhaust gas is still small at the early stage of ignition of the cold start, and the flow path resistance of the exhaust gas passing through the heat exchanger 29 is large, so that the through hole 3 provided in the side wall of the combustion chamber 16 is used.
This is because it is easy for the exhaust gas to flow out. Therefore, the thermocouple 1 has a problem in that the exhaust gas flowing out transiently is sensitively detected, and the exhaust gas is erroneously determined to be blocked and the fire is extinguished.

Further, as shown in FIG. 4B, the high temperature exhaust gas from the through hole 3 becomes local high temperature exhaust gas as the exhaust gas is blocked, and an exterior (front cover) provided on the front surface of the combustion chamber 16 is used. There was also a problem that the coated surface of the exterior was discolored by the high temperature, hitting the back surface of 40).

The exhaust gas obstruction detection device of the present invention solves the above-mentioned problems and enables stable electromotive force to be obtained even if there are some variations in related dimensions, and it is possible to extinguish a fire by making an erroneous determination at cold start. It is an object of the present invention to provide an exhaust blockage detection device that does not have the

[0008]

SUMMARY OF THE INVENTION An exhaust gas obstruction detection device of the present invention for solving the above problems includes a burner that burns a mixture of fuel gas and air, and an on-off valve that opens and closes a gas flow path to the burner. Used in a combustor including a heat exchanger that heats running water with combustion heat from the burner, and a combustion chamber formed between the heat exchanger and the burner, and forms a through hole in a sidewall of the combustion chamber. However, a thermocouple that generates an electromotive force by heating by the exhaust gas flowing out from the through hole when the exhaust of the heat exchanger is blocked is provided, and the on-off valve is closed based on the electromotive force level of the thermocouple to perform combustion. In the exhaust blockage detection device to be stopped, the hot junction of the thermocouple is provided with a heat capacity body having a projected area in the through hole direction of 1 to 1/3 with respect to the opening area of the through hole. Is the gist.

The exhaust blockage detecting device of the second invention is the exhaust blockage detecting device of the first invention, wherein the thermocouple of the thermocouple is set with respect to the distance between the hot junction of the thermocouple and the through hole surface. The gist is that a wide separation distance is provided between the cold junction and the side surface of the combustion chamber.

[0010]

In the exhaust gas obstruction detection device of the first aspect of the present invention having the above-mentioned structure, the heat capacity body having a projected area in the direction of the through hole of 1 to 1/3 with respect to the opening area of the through hole is used as the thermocouple. Provide at the hot junction of. That is, the increase in electromotive force can be delayed by the amount of heat absorbed by the heat capacity body at the initial stage of ignition. Therefore, even if there is a transitional outflow of exhaust gas from the through hole at the initial stage of ignition, electromotive force is not generated sensitively, and there is no extinguishing in which combustion is stopped due to a false determination as abnormal. Further, the heat capacity body is provided with a size of 1/3 of the opening area of the through hole, so that the exhaust gas temperature of the entire through hole is averaged and transmitted to the hot junction of the thermocouple. Therefore, even if the relational dimension position between the hot junction of the thermocouple and the through hole is slightly shifted, the amount of heat absorbed by the heat capacity body does not change, and the electromotive force generated by the thermocouple does not vary. That is, mass productivity in manufacturing can be improved.

Further, the exhaust blockage detecting device of the second invention is
The distance from the cold junction of the thermocouple to the side surface of the combustion chamber is set larger than the distance from the hot junction of the thermocouple to the through hole surface.
That is, since the cold junction of the thermocouple is provided away from the side surface of the high temperature combustion chamber, and the hot junction of the thermocouple is provided close to the through hole surface, it is difficult for one cold junction to transfer heat from the high temperature combustion chamber. The other hot junction is reliably heated by the exhaust gas flowing out from the through hole. Therefore, when the exhaust gas is blocked, the temperature difference between both contacts becomes large, and a high electromotive force can be obtained. That is, it is possible to improve the sensitivity of the exhaust blockage detection device as a sensor.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the structure and operation of the present invention described above, preferred embodiments of a water heater equipped with the exhaust blockage detecting device of the present invention will be described below. Water heater
As shown in FIG. 1, a burner 28 that burns a mixture of fuel gas and primary air, a heat exchanger 2 that transfers combustion heat to running water.
9. A combustion chamber 16 that is sandwiched between the heat exchanger 29 and the burner 28 to form a combustion space is provided.

The burner 28 is provided with a primary thermocouple 30 for detecting an combustion state by generating an electromotive force by heating by a combustion flame, and a secondary thermocouple 1 for detecting exhaust blockage is provided in the combustion chamber 16
It is provided so as to face the through hole 3 provided on the side wall of the and is electrically connected to the controller 23 that monitors the detected electromotive force. The controller 23 includes a primary thermocouple 30 and a secondary thermocouple 1.
If it is determined that the combined electromotive force is equal to or less than a predetermined value, and if it is determined to be abnormal, a valve closing command is issued to the on-off valves 24 and 25 of the gas flow path electrically connected to the controller 23 to stop combustion. .

When the interior of the primary thermocouple 30 becomes an oxygen-deficient atmosphere due to combustion exhaust gas, the combustion flame heating the primary thermocouple 30 starts to lift (fly) and the generated electromotive force is reduced. On the other hand, in the secondary thermocouple 1 which is the exhaust blockage detecting device, when the exhaust flow path of the heat exchanger 29 is blocked by the combustion products, the exhaust gas begins to overflow from the through hole 3 provided in the side wall of the combustion chamber 16. , Detects this overflowed exhaust gas and generates electromotive force. Further, the secondary thermocouple 1 is connected to the primary thermocouple 30 in reverse polarity so as to generate a counter electromotive force, and the generated electromotive force rises as the exhaust passage of the heat exchanger 29 is closed, The combined electromotive force of the primary thermocouple 30 and the secondary thermocouple 1 is reduced. Therefore, the combustion controller 2
Numeral 3 not only detects the oxygen deficiency state, the misfire and the disappearance of the combustion flame from the combined electromotive force value, but also detects the closed state of the heat exchanger 29.
Valves 4 and 25 are closed to prevent incomplete combustion.

As shown in FIG. 2D, the hot junction support portions 5 and 6 forming the secondary thermocouple 1 are made of different metals such as chromel and constantan, and the welded connection portions are the hot junction 2. To form. At the other end, connecting wires 9 and 10, which are respectively coated copper wires, are welded, and these connecting portions form cold junctions 7 and 8. The hot junction support 5 is the hot junction support 6
Therefore, the cold junction 7 is provided at a higher position and longer, and the cold junction 7 is provided at a position farther from the hot junction 2 than the cold junction 8. The cold junctions 7 and 8 are covered by the glass tube 11,
It is electrically insulated. The outer circumference is crimped and integrated by a fixing member 12 so that the hot junction support portions 5 and 6 are positioned in parallel (FIG. 2 (A)). The side wall of the combustion chamber 16 is provided with a mounting plate 15 for mounting the secondary thermocouple 1.
An attachment hole 17 larger than the through hole 3 is provided so as to communicate with the combustion chamber 16. The secondary thermocouple 1 is provided laterally so as to horizontally separate the cold junctions 7 and 8 from the hot junction 2, and between the secondary thermocouple 1 and the mounting plate 15, the through hole 3 is opened depending on the gas species. One end of the through hole changing plate 19 whose area is selected and used is sandwiched and fixed by a mounting screw 14. The other end of the through hole changing plate 19 closes the mounting hole 17 and is hooked on the back side of the edge of the mounting hole 17, and a through hole 3 smaller than the mounting hole 17 is provided at a position corresponding to the center of the mounting hole 17. The size of the through hole 3 selected according to the gas type is set such that, for example, LP gas has a length of 9 mm × width of 5 mm, and city gas has a width of 5 mm so as to detect exhaust blockage and appropriately stop combustion within a good combustion limit. 4C
The gas is provided with a size of 5 mm in length and 4 mm in width. Further, in the secondary thermocouple 1, the projected area in the direction of the through hole 3 is 1 to the opening area of the through hole 3 so as to wrap the hot junction 2.
A cylindrical heat capacity body 4 having a size of 1/3 is provided. If the size of the heat capacity body 4 is larger than that of the through hole 3, the heat radiation increases and it becomes difficult to heat the electromotive force of the secondary thermocouple 1 and the electromotive force is easily influenced by the room temperature. Become. In addition, with respect to the opening area of the through hole 3, the through hole 3
If the projected area in the direction is less than ⅓, the effect described later cannot be obtained. Therefore, it is preferable that the diameter is 4 mm and the length is 5.
A heat capacity body 4 having a size of mm is provided. In addition, the heat capacity body 4
Is wrapped around the hot junction 2 with a brass material having a large heat capacity and fixed to the hot junction 2 so as not to be displaced by caulking.

Next, the reason for providing the heat capacity body 4 on the hot junction 2 will be described in detail below. The first reason is to prevent the gas flow passage from being extinguished due to an erroneous determination in the initial stage of ignition. At the time of ignition (called cold start) when the water heater is completely cold, the draft force of the combustion exhaust gas is small even when the exhaust gas is not blocked, and the exhaust gas flow path that passes through the heat exchanger 29 is also present. Great resistance. Therefore, at the cold start, the exhaust gas transiently flows out from the through hole 3 until the temperature of the entire combustion chamber 16 rises. However, the heat capacity body 4
Absorbs the heat quantity of the exhaust gas flowing out transiently and delays the rise of the electromotive force generated in the hot junction 2. In other words, since the hot junction 2 of the secondary thermocouple 1 does not sensitively detect this transient exhaust gas, if exhaust plugging does not occur at cold start, it will not be erroneously determined as abnormal and combustion will stop. do not do. That is, disappearance does not occur. On the other hand, when the exhaust gas is blocked, the exhaust gas continues to flow out from the through hole 3 and the electromotive force rises, and it is determined to be abnormal, and the combustion is stopped.

The second reason is to reduce variations in generated electromotive force. The heat capacity body 4 is provided in the size of 1 to 1/3 of the area of the through hole 3, and even if the relative dimensional position with respect to the through hole 3 is slightly deviated, the total volume of exhaust gas flowing out from the through hole 3 is increased. Exposed. That is, the exhaust gas heat amount of the entire through hole 3 is absorbed, averaged, and transferred to the hot junction 2. Therefore, the electromotive force does not fluctuate even if the relative dimension positions are slightly displaced. Further, since the hot junction support portions 5 and 6 of the secondary thermocouple 1 are provided so that the projection of the through hole 3 in the opening direction is applied to the upper and lower edges of the through hole 3, the secondary thermocouple 1 is slightly displaced. Even if it does, the amount of protrusion of the portion facing the through hole 3 is practically unchanged. In particular, as shown in FIG. 3, if the hot junction support portions 5 and 6 are provided so as to project above and below the through hole 3, the influence is completely eliminated. Further, even if the amount of protrusion from the side edge with respect to the through hole 3 changes and the heating area due to exhaust gas changes, the increase or decrease in the amount of protrusion of the hot junction 2 support portion is much smaller than the heat capacity of the heat capacity body 4. . Therefore, the influence of the protruding amount of the hot junction support portion on the electromotive force can be ignored. That is, even if there is some variation in the related dimensions, the detection performance is stable, and the mass productivity in manufacturing can be improved.

The third reason is that the front cover 40
This is to prevent discoloration of When the exhaust gas is blocked, the exhaust gas flows out from the through hole 3 and concentrates on a part of the back surface of the front cover 40, and the paint surface of the front cover 40 may be discolored by the exhaust gas temperature. However, by providing the heat capacity body 4, heat in the exhaust gas is absorbed by the heat capacity body 4 in the early stage of combustion, and the exhaust gas outflow direction is dispersed by the heat capacity body 4 in the case of combustion. Therefore, the heat capacity body 4 prevents the hot exhaust gas from flowing through the front cover 4
The front cover 40 is prevented from discoloring by not locally contacting the back surface of 0 (FIG. 2B).

Next, the improvement of the sensitivity of the exhaust blockage detecting device as a sensor will be described in detail below. The secondary thermocouple 1
If the hot junction 2 and the cold junctions 7, 8 are kept at different temperatures, thermoelectromotive force is generated according to the temperature difference. That is, when the exhaust gas is blocked, a larger counter electromotive force can be generated as the temperature difference between the hot junction 2 and the cold junctions 7 and 8 increases. Therefore, the following is performed to increase the temperature difference. First, the upper hot junction support 5 is made longer than the lower hot junction support 6, and a distance is provided between the hot junction 2 and the cold junction 7. When the exhaust gas begins to be clogged with exhaust gas, the amount of the exhaust gas overflows upward from the through hole 3 and the temperature is high. Therefore, the upper hot junction support 5 and the cold junction 7 are likely to have a higher temperature than the lower hot junction support 6 and the cold junction 8. Therefore,
A longer temperature difference can be obtained between the hot junction 2 and the cold junction 7 by making the hot junction support 5 located above the length longer than the hot junction support 6 located below (FIG. 2D).

By providing this difference in length, another advantage can be obtained. Conventionally, as shown in FIG.
, Each of the hot junction supports 5, 6 made of different materials
In order to make a distinction at the time of welding, the hot junction 2 was provided so as to be displaced. For example, before the welding, the hot junction 2 is deviated in order to prevent the same material from being erroneously welded, and after the welding, to identify which material is in the plus or minus direction of the electromotive force. The hot junction support portions 5 and 6 are provided at the positions, and the hot junction support portions 5 and 6 are discriminated by the difference in shape. For this reason, the hot junction 2 approaches the bent portion 31 of the hot junction support portion 5 and welding is difficult at the corners, and welding is difficult. Further, since the melting margin due to welding is included, the length before and after welding is different. Therefore, the distinction between the hot junction support portion 5 and the hot junction support portion 6 was unclear with a slight difference in length. Moreover, if the heat capacity body 4 is provided so as to enclose the hot junction 2, it becomes impossible to determine after the welding. However, in this embodiment, as shown in FIG.
As shown in (d), the determination before and after welding of each of the hot junction support parts 5 and 6 is performed by lengthening the hot junction support part 5 and shifting the position of the cold junction 7 to determine the position of the cold junction 7. You can easily do it from the difference. Further, since the hot junction 2 is provided at the center position away from each of the bent portions 31, 31, the welding work is facilitated.

Further, in order to increase the temperature difference, the cold junctions 7 and 8 are provided apart from the combustion chamber 16. In other words, when the exhaust chamber begins to become clogged, the combustion chamber 16 begins to reach a high temperature, and at this time, the cold junction 7 secures an appropriate distance from the combustion chamber 16 so that the temperature of the cold junction 7 does not rise. For example, as shown in FIG. 2C and the conventional example in comparison with FIG. 4C, the hot junction support portions 5 and 6 between the cold junction and the hot junction are arranged in the combustion chamber 16 direction. By bending, the separation distance between the cold junctions 7 and 8 and the combustion chamber 16 is made larger than the separation distance between the hot junction 2 and the through hole surface (H0 dimension). That is, by increasing the separation distance between the cold junctions 7 and 8 and the combustion chamber 16, a large temperature difference is obtained when exhaust gas is blocked, and a large electromotive force is generated. That is, it is possible to improve the sensor sensitivity of the secondary thermocouple 1 as the exhaust blockage detection device.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it is needless to say that the present invention can be implemented in various modes without departing from the spirit of the present invention. Is. For example, in the present embodiment, the primary thermocouple 30 and the secondary thermocouple 1 are provided in series to monitor the combined electromotive force, but the electromotive force of each thermocouple may be monitored separately. . Further, it may be an exhaust blockage detection device that closes the gas flow path by closing the magnet type safety valve connected in series with the thermocouple by decreasing the electromotive force of the thermocouple.

The heat capacity body 4 is not limited to the cylindrical shape according to the embodiment, but may be a spherical shape or a rectangular shape in which the shape of the through hole is reduced. Further, it may have a shape in which a plate material / wire material is wound around the hot junction. Secondary thermocouple 1
The metal forming the is not limited to the combination of chromel and constantan according to the embodiment, and may be a combination of chromel and alumel, a combination of iron and constantan, or another combination such as copper and constantan. The material of the heat capacity body may be copper, lead, iron, aluminum, zinc, or an alloy thereof, as long as it has a heat capacity. In addition, the secondary thermocouple 1 is used in the embodiment (Fig.
As shown in (c)), the bending dimension H0 is not limited to be provided between the hot junction 2 and the cold junctions 7 and 8, and the secondary thermocouple 1 is obliquely attached to burn the cold junctions 7 and 8 with each other. A separation distance from the chamber 16 may be secured. In addition, in the present embodiment, the water heater in which the secondary thermocouple 1 is provided in the combustion chamber 16 below the heat exchanger 29 together with the primary thermocouple 30 that generates an electromotive force by facing the combustion flame of the burner has been described. Secondary thermocouple 1
It may be applied to another combustor in which only the primary thermocouple 30 is provided and the primary thermocouple 30 is not provided.

[0024]

As described above in detail, according to the exhaust gas clogging detection device of the present invention, fire extinguishing due to an erroneous determination is prevented at the time of cold start, so that the usability is improved, and the variation of the related dimensions of the thermocouple is prevented. Since the generated electromotive force difference is small, the yield in manufacturing is improved and mass productivity is improved, and further, the sensor sensitivity for exhaust gas clogging detection is improved, and high safety can be secured. Further, in the exhaust gas clogging detection device of the second invention, since a high electromotive force can be obtained in the thermocouple which is the sensor when the exhaust gas is blocked, the exhaust gas clogging is reliably detected,
The safety can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a water heater.

FIG. 2 is a schematic diagram of an exhaust blockage detection device according to an embodiment of the present invention.

FIG. 3 is a schematic view of an exhaust blockage detection device showing another embodiment of the present invention.

FIG. 4 is a schematic view of an exhaust blockage detection device according to a conventional example.

[Explanation of symbols]

 1 Secondary Thermocouple 2 Hot Junction 3 Through Hole 4 Heat Capacity 7 Cold Junction 8 Cold Junction 16 Combustion Chamber 19 Through Hole Change Plate

Claims (2)

[Claims] 1. A burner that burns a mixture of fuel gas and air, an on-off valve that opens and closes a gas flow path to the burner, a heat exchanger that heats running water with combustion heat from the burner, and the heat It is used in a combustor having an exchanger and a combustion chamber formed between the burners, forms a through hole in the side wall of the combustion chamber, and causes exhaust gas flowing out from the through hole when exhaust heat of the heat exchanger is blocked. A thermocouple that generates electromotive force by heating is provided, and in the exhaust blockage detection device that closes the on-off valve and stops combustion based on the electromotive force level of the thermocouple, the hot junction of the thermocouple is connected to the hot junction. An exhaust blockage detecting device comprising a heat capacity body having a size of the projected area in the through hole direction of 1 to 1/3 with respect to the opening area of the hole. 2. The separation distance between the cold junction of the thermocouple and the side surface of the combustion chamber is set wider than the separation distance between the hot junction of the thermocouple and the through hole surface. The exhaust blockage detection device according to 1.