JPS6020024A - Safety combustion device - Google Patents

Abstract

PURPOSE:To prevent errorneous operation of a safety device caused by initial action thereof by a method wherein a gas sensor element is arranged downstream of a heat exchanger and a normal value of heating temperature of the sensor element is set less than such a temperature as peak output value generated under ignition of burner is reached to an operating level of a safety means. CONSTITUTION:A gas sensor element S is arranged downstream of a fin 020 at a position corresponding to a central part of the fin 020 with a socket 11. A thermo-coupler element 10 is arranged at a position where it is heated by a pilot burner 012 and is applied for use in sensing a lost fire and arranged at a power supply for driving a solenoid valve 04 acting as safety means. The normal value of heating temperature of the gas sensing element S is set at a value less than a temperature where the output peak value of the gas sensor element kept at a room temperature under ignition of the burner is reached to the operating level of the safety means 04. Thereby, it is possible to prevent an errorneous operation of the safety device caused by the initial action.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention 1] The present invention relates to an improvement of a combustion safety device for detecting incomplete combustion in combustion equipment having a heat exchanger, such as a small household stove. More specifically, the present invention is an apparatus that detects misfire in this type of combustion equipment using a thermoelectric element, and uses the electromotive force obtained from the thermoelectric element at the time of ignition as a power source to detect incomplete combustion using a gas detection element. Regarding.

[Terminology J The characteristics of the device of the present invention vary depending on the thermal time constant of the gas detection element. Therefore, the method for measuring the "thermal time constant" of the gas detection element is determined as follows.

(1) Incorporate the device into the combustion equipment to be used and leave the whole thing at room temperature.

(2) Ignite the burner, heat the element with exhaust gas, and establish a temperature increase pattern.

Note that for equipment that has a pilot burner in addition to the main burner, both should be ignited at the same time if possible.

(3) Calculate the steady heating temperature (Tf) of the element and the difference (ΔT) between the steady heating temperature and the room temperature, and calculate the time until the temperature (Ts) of the element becomes Ts=Tf-e''·ΔT. 1/2 of this time is defined as a thermal time constant.

The characteristics of the device are affected not only by the temperature increase rate of the element but also by the temperature decrease rate. However, since the temperature decreasing rate is determined in accordance with the temperature increasing rate, the thermal time constant is defined using the temperature increasing rate. Furthermore, since the influence on the characteristics of the device is determined by the temperature increase/decrease pattern around the steady heating temperature (Ts), the thermal time constant is defined by giving weight to temperature changes around the steady heating temperature (Ts).

Next, "pulse noise" refers to a phenomenon in which, when the burner is re-ignited at short intervals of, for example, one commonality, the output of the gas detection element increases abnormally immediately after the re-ignition. Pulse noise is
This occurs when the gas detection element is sensitive to a large amount of incomplete combustion components, such as CO gas, generated from the burner immediately after ignition. Pulse noise is a phenomenon that widely occurs in various types of combustion equipment.

Conventional technology] Burner misfire is detected by a thermoelectric element, and incomplete combustion is detected by S.
It is known from Utility Model Application Publication No. 58-704'6 that detection is performed using a gas detection element such as nO2. This technology reduces power consumption by heating the element with exhaust gas, and uses the electromotive force from the thermoelectric element as a power source, eliminating the need for an external power source.

It is also known from JP-A-56-80584 to detect incomplete combustion in a water heater using a gas detection element of this type. There, a gas detection element and a sintered body of TeT 102, Cr 20B, Co 304, etc. are used, and the element is heated to 600 to 900''C by exhaust gas to detect CO produced by incomplete combustion. .

As a characteristic of a gas detection element using a metal oxide semiconductor such as SnO2 or TiO3, the sensitivity to fl) Co increases as the temperature decreases, but the response speed decreases as the temperature decreases.

(2) When an element that has been left for a long time is heated again, the resistance value of the element temporarily decreases (hereinafter this phenomenon is referred to as "initial action").

It is known.

[Problems to be solved by the invention] The problems to be solved by the present invention are as follows: ++1 Preventing malfunction of safety devices due to initial action, (2) Decreasing the thermal time constant of the gas detection element to shorten the dead time until detection of incomplete combustion becomes possible. (3) Eliminate pulse noise caused by turning the burner on and off; (4) Find a location for installing the gas detection element suitable for solving these problems.

The reason why the dead time has become a problem is that the thermal time constant of the gas detection element is large, and the time required to detect incomplete combustion after ignition of the burner is often 10 minutes or more.

Pulse noise is a phenomenon discovered by the inventors.When the burner is re-ignited after a short interval (for example, one minute), the output of the element increases in a pulse-like manner.If this phenomenon is left unchecked, the safety device will be activated every time the burner is ignited. will malfunction. This phenomenon occurs only when the burner is re-ignited after the burner has been extinguished and before the gas detection element has completely cooled down, and is different from the initial action that occurs when the burner is left unused for a long period of time.

A secondary issue regarding the installation location of the gas detection element is:
Sometimes it is possible to find a position where the exhaust gas is mixed uniformly and there is no uneven mixing of the exhaust gas from the primary air and the exhaust gas from the secondary air. To solve the problem of uneven mixture of exhaust gas, it is necessary to prevent malfunctions of safety devices caused by partial molecular mixture Bunsen burners and petroleum fuel burners, find the appropriate installation position of gas detection elements, and minimize malfunctions caused by pulse noise. purpose.

A second invention of the present application aims to further shorten dead time and reduce malfunctions due to pulse noise.

In addition to the first invention, the third invention of the present application aims to prevent malfunctions caused by pulse noise.

[Structure of the Invention] The first invention of the present application uses a thermoelectric element to detect a burner misfire in a combustion device that heats a burner, a heat exchanger, and a fluid, and detects gas sensitivity due to exhaust gas from the burner. A gas detection element that uses changes in the resistance value of a metal oxide semiconductor is heated to a temperature that allows detection of CO gas, and incomplete combustion is detected using the electromotive force obtained from the thermoelectric element when the burner is ignited as a power source. In the device in which the safety means is activated in the event of misfire or incomplete combustion of the burner, the gas detection element is installed at a position downstream of or inside the heat exchanger where ambient air does not mix, and the gas detection element is heated. The combustion safety device is characterized in that the steady-state value of the temperature is set to be lower than the temperature at which the peak value of the output at the time of burner ignition of the gas detection element left at room temperature reaches the operating level of the safety means.

The second invention of the present application further reduces the thermal time constant of the gas detection element to 120 seconds or less, shortens the dead time of the element when the burner is ignited, and promotes cooling of the element after the burner is extinguished to prevent gases caused by pulse noise. This is to reduce the output of the detection element.

A third invention of the present application provides a pulse noise malfunction prevention means in addition to the first invention.

In many combustion devices, combustion is performed using not only primary air but also a combination of primary air and secondary air. If there is uneven mixing between the exhaust gas from the primary air and the exhaust gas from the secondary air, the accuracy of detecting incomplete combustion will decrease. However, if a gas detection element is installed downstream or inside the heat exchanger, the exhaust gas will be completely mixed during the process of passing through the heat exchanger, and the problem of uneven mixing will be solved.

The exhaust gas is cooled by the heat exchanger, and the heating temperature of the element is also lowered. Since the sensitivity to CO gas increases at low temperatures, the element can be placed at a temperature suitable for detecting CO gas.

In the present invention, since the electromotive force from the thermoelectric element is used as the power source,
It is not possible to heat-clean the gas detection element or cut off the output from the element until the initial action is completed (usually for 3 to 5 minutes). Rather than eliminating the phenomenon of initial action from the gas detection element, it will last a long time if the safety means does not malfunction due to the initial action. After examining the relationship between the initial action and the heating temperature of the element, we found that f+)
It was found that the lower the heating temperature, the smaller the peak of the element's output during the initial action. (2) Lowering the heating temperature lengthens the time the initial action lasts. Sensitivity to CO gas increases at low temperatures. When the heating temperature of the element is lowered, the peak of the initial action decreases, the sensitivity to CO gas increases, and the influence of the initial action becomes significantly smaller. Therefore, by focusing on the peak of the output of the element at the time of the initial action, the steady υ thermal temperature of the element can be determined so that the safety means will not malfunction even due to the peak of the output.

In this way, the period of the initial action becomes significantly longer by one. During this time, a danger arises if the element is not sensitive to CO gas. However, if the element is heated close to the steady heating temperature during the initial action, then C
It was confirmed that O gas could be detected.

It has been found that when the gas detection element is heated by exhaust gas from a burner, the thermal time constant of the element becomes extremely long.

This thermal time constant mainly depends on the protective cover used for the device. For example, 100 mm made of stainless steel wire with a wire diameter of approximately 100 μ
Mesh (Even if the mesh is determined by the number of wires included in the length of 1 inch, the peak of the output at the initial action will hardly change.The response to CO gas will be significantly slower at low temperatures, so when the element is heated When the constant becomes large, the dead time when igniting the burner increases significantly.To reduce the dead time, reduce the heat capacity of the element, especially the heat capacity of the cover, and the heat conduction from the metal oxide semiconductor, and increase the thermal time constant. Make sure that the time is 120 seconds or less.

The heating temperature and thermal time constant of the gas detection element change the output during /N6 noise. The rust noise is caused by the generation of a large amount of incomplete combustion components (often cases where the CO gas concentration in the exhaust gas is 500 pprn or more) immediately after the burner is ignited. If the element is sufficiently cooled at the time of pulse noise, the response of the element to CO gas is slow at low temperatures, and pulse noise does not occur. By lowering the heating temperature of the element and setting the thermal time constant to 120 seconds or less, the influence of pulse noise can be reduced.

If the burner is re-ignited almost simultaneously with extinguishing, malfunctions due to pulse noise cannot be prevented no matter the element heating temperature or thermal time constant.

However, the time when pulse noise becomes a problem is 1 to 3 after ignition.
Since the duration is about seconds, it is easy to prohibit the operation of the security means during this time even if the power supply capacity is limited. easy C
By providing a '-R timer or the like and prohibiting the operation of the safety means while the timer or the like is in operation, malfunctions due to pulse noise can be eliminated.

[Example 1 Next, embodiments will be described, focusing on preferred embodiments.

In FIGS. 1 and 2, (02) is a water heater as an example of a combustion device, but any other combustion-like device may be used as long as it is equipped with a heat exchanger. The water heater (02) is equipped with a Bunsen burner (010) Q via a normally closed solenoid valve (o4), a diaphragm valve (06), and a damper for primary air intake (o8). Instead of the Bunsen burner (010), other burners, such as oil-fueled burners, may be used. A branch pipe is provided downstream of the solenoid valve (04) and a pilot burner (012) is provided. The solenoid valve (04) is manually opened by pressing the cock (014) for igniting the pilot burner (012).
14) operates an ignition mechanism (not shown) to ignite pilot burner (012)K.

By rotating the water supply cock (016), the water supply pipe ((1
Fin (020) as a heat exchanger with embedded 18)
At the same time, a change in the water pressure of the water supply pipe (018) is detected and the diaphragm valve (o6) is opened, and the Bunze 7
(010) is ignited. Pilot burner (012
) kith and only the Bunsen burner (010) as the main burner may be used. Since the structure and function of this water heater (o2) are already well known, detailed explanation will be omitted.

In the wake of the fin (020) (upper part in the figure), the fin ('
020) at a position corresponding to the center of the socket (11).
A gas detection element (S) is provided using the following. The temperature of the exhaust gas at this position is approximately 60° C. when only the pilot burner (012) is ignited, and approximately 270° C. when the Bunsen burner (olo) is also ignited. Gas detection element (
At the rear of S), there is an exhaust gas outlet (022) and a hood (02
4, l is provided. The installation position of the gas detection element (S) is
When increasing the heating temperature, for example, a part of the fin (020) is hollowed out to form the inside of the fin (020) or the side circumference of the fin (020). This position is also completely equivalent to the inside of the fin (020) in the original sense in terms of uneven mixing of exhaust gas or temperature of exhaust gas, so such a position is also called the inside of the heat exchanger. I'll decide. In other words, the inside of the heat exchanger means a position where the exhaust gas is uniformly mixed behind the front surface of the heat exchanger, focusing on the flow of the exhaust gas. lowering the temperature of exhaust gas,
Alternatively, when there is no space between the fins (020) and the exhaust gas outlet (022), a gas detection element (S) is provided behind the exhaust gas outlet (022). In this case, in order to prevent the ambient air from getting mixed in, the gas detection element (S) should be placed downstream (upper part of the diagram) of the central part of the exhaust gas outlet (022), or a chimney (not shown) may be provided so that the element (S) can be placed inside the exhaust gas outlet (022). It should be provided in

At the position heated by the pilot burner (012),
A thermoelectric element (lO) such as a thermopile is provided and used for detecting misfire and as a power source for driving the gas detection element (S) and the electromagnetic valve (04) as a safety measure. As a thermoelectric element (lO),
It is also possible to use a device that utilizes thermoelectromotive force at a semiconductor junction. In this example, two burners are used, and the burner associated with the thermoelectric element (10) is the pilot burner (0
In 12), the burner related to the gas detection element (S) is a Bunsen burner (010).

The structure of the gas detection element (S) is shown in FIG. This element (
S) is 1 part by weight of Pd in 1 part by weight of S n O21,O0
The element body (S2) is made by adding elements and sintering after molding.
It is said that A pair of coiled noble metal electrodes (S4) and (S6) are connected to the element body (S2), and each end of the noble metal electrodes (S4) and (56) is connected to the base (S8).
Four lead pins (S10a) fixed to.

(S10b), (S10c), (s10d')
Fixed to. In order to protect the element body (S2) from oil, dust, etc., a cover (S12) made of double gold copper made of 20 mesh stainless steel wires with a wire diameter of about 100 μm is provided. When this element (S) is installed in the position shown in Figures 1 and 2, the steady value of the heating temperature of the element body (S2) is approximately 50°C when only the pilot burner (012) is ignited, and the steady value of the heating temperature of the element body (S2) is approximately 50°C when only the pilot burner (012) is ignited, and IO) is also 185°C when ignited.
It became. (The temperature of the gas detection element (S) in this specification means the temperature of the element body (S2).) The thermal time constant during temperature rise was still 64 seconds. In this case, the room temperature is 2
It was 0°C. (Hereinafter, each measurement was performed at a room temperature of 20°C.) The characteristics of the element body (S2) depend on the type of metal oxide semiconductor (
Here S'n O3) and additive (here 1)
d). The type of semiconductor and additives change the characteristics of the element body (S2), but the effect is different from the element body (S2).
This is close to shifting the temperature dependence of S2) almost in parallel. Among each semiconductor, SnO2 operates at the lowest temperature, and when increasing the temperature by 30°C in In2O3, SnO2
The same characteristics can be obtained. For ZnO, it is better to increase the heating temperature by about 80°C than for SnO,2. Instead of P'd, P
t, Rh, Ir, Os.

A noble metal element such as Ru or Au may be added. Adding these things allows the element body (S2) to operate at a lower temperature. In the case of the example in which 1 part by weight of Pd was added, the same characteristics could be obtained at a temperature about 70° C. lower than in the case of not adding Pd or the like. These additives are gradually oxidized by heating and gradually reduced by contact with CO and the like. The existence of additives is quite complex. The amount added is preferably 0.1 to 5 parts by weight in terms of metal per 100 parts by weight of the metal oxide semiconductor. The material that operates at the lowest temperature is a material in which 1 part by weight of Pd and 0.1 part by weight of Au are added to 100 parts by weight of S n 02, which is about 20°C lower than that of the example. It worked with temperature.

Examples of preferred metal oxide semiconductors and additives are shown in Table 1.

Table 1 5n02 1. OPd, 140~2'00 185S
nOO, 5Pd 150-210190Sn02. OP
d 180-1901705nO20,2Pd 170
~240210S 11□1. OPt 150-210
190 Without SnO3 210~270 2501+12
03 None 240-300 280In20.1. O
Pd, 180-240220 without ZnO 280-3
50 330 *1 Indicates the number of parts by weight added in terms of metal to 100 parts by weight of metal oxide semiconductor.

The optimum heating temperature for the gas detection element (S) varies depending on the material. When installing the element (S), change the position and heat dissipation conditions.
By selecting a temperature suitable for each material, performance similar to that of the example can be obtained.

The temperature of the element body (S2) is
It is determined by heat conduction through (S12). Therefore, these are selected so that an appropriate steady heating temperature can be obtained.

The thermal time constant of the element body (S2) is mainly determined by cuckoo (S2).
12) The size is determined based on the air permeability and heat capacity. A preferable cover (Si2) is a gilt-copper type having a small heat capacity, 60 meshes or less, and a thermal time constant of the element (S) of 120 seconds or less. If there is no need to fear contamination by cold oil, dust, etc., the thermal time constant can be reduced by eliminating the heat loss by <-(Si2)'.

Note that the above description is based on the premise of an N-type metal oxide semiconductor such as S, n O2, and I n 203° ZnO. In addition to this, gas-sensitive metal oxide semiconductors include Cp.
P-type metal oxide semiconductors such as B 04 and NiO also exist. In a P-type semiconductor, contrary to an N-type semiconductor, the resistance value increases due to CO gas, and also due to initial action and pulse noise. However, since a gas detection element using a P-type semiconductor has not yet been put into practical use, a description thereof will be omitted below. When a P-type semiconductor is used, the ancillary circuit may be modified so that an increase in resistance value is output.

Fig. 4 shows a modified gas detection element (cf'I). This element (S') houses the element body (S2) in a through hole provided in an insulating substrate (S14) made of alumina or the like. A pair of noble metal electrodes (S4), (S6) and the element body (S2)
was supported. and 20 meshes of gilt bronze (S
12') to cover the through hole and protect the element body (S2).

In addition, the noble metal electrodes (S4) and (S6) are fixed to the substrate (S14) using an inorganic adhesive, etc., and the ends are connected to lead pins (8).
18).

Connect to (520). Furthermore, a pair of through holes (S20a
).

(S20b) etc., so that the element (S') can be fixed to the socket (11) at equal pressure with bolts, nuts, etc.

A circuit of the embodiment is shown in FIG. 5(A).

As the thermal lightning element (10), about 10 thermocouples such as chromel-alumel are connected in series, and an electromotive force of about 200 mV is obtained when the pilot burner (012) is ignited. The thermoelectric element (10) includes a germanium transistor (12) as part of pulse noise malfunction prevention means.
The series piece of the gas detection element (S) and the load resistor (RL) is connected through. Germanium transistor for control (
14) and a solenoid valve (04) are provided in series, and the base of the germanium transistor (14) is connected between the gas detection element (S) and the load resistor (RL). and the load resistance (
Adjust the resistance value of RL) until the CO concentration in the exhaust gas is 500.
p p m (based on capacitance ppm, the same applies hereinafter).

), the transistor (14) turns off and the solenoid valve (04)
closes.

A three-point switch (16) is provided that opens and closes in conjunction with the water supply cock (016) (actually, in conjunction with the on/off of the Bunsen burner (010)). switch (16)
Through the capacitor (18) of about 500μF and 8O
Connect a resistor (20) of about KΩ and turn on a Bunsen burner (
Simultaneously with the ignition of 010), the capacitor (18) is charged with a time constant of about 15 seconds. During the charging period of the capacitor (18), the germanium transistor (12) is turned off, and the solenoid valve (04) is turned off regardless of the output of the gas detection element (S).
to be opened. In addition, at the same time as the Bunsen burner (010) is extinguished, the switch (16) is switched and the capacitor (
18) is quickly discharged. In this way, a pulse noise malfunction prevention means is constructed.

What is necessary to prevent pulse noise malfunction is to turn off the solenoid valve (0
4) to prevent it from closing. Therefore, 20 seconds is sufficient for the pulse noise malfunction prevention means to act. In case the Bunsen burner (010) is frequently turned on and off, it is preferable to return to the initial state (when extinguished) at the same time as the Bunsen burner (010) is extinguished.

Another example of a circuit equipped with pulse noise malfunction prevention means is shown in the fifth section.
Shown in Figure (B). In this circuit, a delay circuit consisting of a resistance chamber) and a capacitor (+8) is provided on the output side of the gas detection element (S), and the output of the gas detection element (S) is delayed for several seconds. This is what I tried to convey to you.

In addition, as shown in FIGS. 6(A) and 6(B), a Bunsen burner (
010) may be detected and the thermal time constant of the heat sensitive element (22) may be used to prevent malfunction. In this case, when extinguishing the Bunsen burner (010), the heat-sensitive element (in order to promote cooling, the heat radiator (26) is extinguished by the crank mechanism (24) linked to the water supply cock (016)). It is preferable to contact the heat sensitive element (22) at the same time.

Note that the illustration of the diaphragm valve (06) is omitted in FIG. 4(B).

Furthermore, as shown in Fig. 7, the ignition of the Bunsen burner (010) is detected using a photoconductive element (c) made of CdS or the like, and a timer made of a capacitor (barb and resistor 6') is charged. Germanium transistor (1
'j may be turned on.

Alternatively, as shown in FIGS. 8(A) and 8(B), a mechanical timer (TI) is provided which is energized in conjunction with the water supply cock (016), and a switch (TI) is provided during the return period of this timer. It is also possible to close the alarm to prevent malfunction.This timer (T1) is connected to the lever (016) by the cock (016).
Attach the three audiences and open the cock (016) to open the barrel (
34) energize the mainspring spring (not shown) housed in the
During the return period of the spring, the tongue (36) closes the switch (3).
0). Then, the escape wheel (38) and pallet stem (40) brake the mainspring spring and determine the time constant of the timer (TI).

The combustion safety device of the embodiment operates as follows.

The solenoid valve (04) is activated by pressing the ignition cock (014).
opens, and the pilot burner (012) is ignited by the rotation of the cock (014). When the electromotive force from the thermal element (lO) increases after ignition, the germanium transistor (14)
is turned on, and the solenoid valve (04) continues to open due to the electromotive force from the thermoelectric element (10). If the pilot burner (012) misfires, the electromotive force from the thermoelectric element (10) decreases and the solenoid valve (04) closes.

When you open the water supply cock (016), the water supply pipe (018)
At the same time, the diaphragm valve (06) senses the change in water pressure and opens, and the Bunsen burner (010) ignites.

The exhaust gas from the Bunsen burner (010) is
The mixture is mixed uniformly in the chamber 20) and cooled to about 270°C. The gas detection element (S) is heated to about 185° C. by this exhaust gas and brought to an operable temperature. If the CO concentration in the exhaust gas becomes 500 pprn or more due to a drop in the oxygen concentration in the room or a blockage in the damper (08), the resistance of the element (S) will change to M or L, and the germanium transistor (14) will turn off. , the solenoid valve (04) closes. Indoor oxygen concentration and CO in exhaust gas in this example
FIG. 9 shows the relationship between the concentration and the resistance value of the element (S).

If a device that has been left unused for a long period of time, for example, one month or more, is restarted, the resistance value of the gas electrode ratio element (S) will abnormally decrease when Bunsen no Des (010) is ignited, and an initial action will occur. Assuming that the steady-state heating temperature of the element (S) is 185°C, the resistance value of the element (S) at the time of initial action is at least twice the resistance value of the germanium transistor (14) at the off level. ) is closed.

Immediately after the Bunsen burner (010) is ignited, incomplete combustion power may fluctuate due to clogging of the damper (08), etc. In this example, the cover (
Since S12) is a 20-mesh wire mesh and the thermal time constant of the element (S) is 64 seconds, the Bunsen burner (010)
The element (S) is heated to about 160° C. about 70 seconds after ignition. At this time, the element (S) is sufficiently heated to a temperature at which it is sensitive to CO gas, and since the element (S) remains sensitive to CO gas even during the initial action, incomplete combustion is detected. The water heater shown in Figures 1 and 2 (02
) to block a part of the damper (08) so that the CO concentration in the exhaust gas was 11,000 pp, and the solenoid valve (04) closed 70 seconds after the Bunsen burner (010) was ignited.

When using a water heater (02) at home, the Bunsen burner (010) may be turned on and off frequently. This eliminates pulse noise from the output of the gas detection element (S). However, after the ignition of the Bunsen burner ■10)
For about seconds, charging of the capacitor (18) is not completed, so the germanium transistor (12) is not turned on. Even if the resistance value of the gas detection element (S) decreases due to pulse noise, the solenoid valve (04) does not close because the collector-emitter voltage of the germanium transistor (12) is large. Even if the Bunsen burner (010) is still frequently turned on and off, the capacitor (18) is instantly discharged each time the Bunsen burner (010) is extinguished, so that the influence of the previous charge does not remain.

The heating temperature and thermal time constant of the gas detection element (S) essentially influence the characteristics of the combustion safety device. Gas detection element (
As S), the material and structure of the example shown in FIG. 3 was used, and the mesh of the cover (S12) was changed to change the thermal time constant. Further, a part of the fin (020) of the water heater (02) was hollowed out so that the element (S) could be installed, and the heating temperature of the element (S) was changed. Instead of the circuit in Figure 5 (A), the gas detection element (S) is connected to a load resistance (RL) and 5V.
Using a circuit connected in series with a constant voltage power supply, the element (S) '7
) The resistance value (R3) was determined. The effects of the heating temperature and thermal time constant of the element (S) will be explained based on FIGS. 10 to 18.

FIG. 10 shows the relationship between the steady-state heating temperature of the gas detection element (S) and the detection sensitivity and response speed to incomplete firing. The detection sensitivity is determined by the resistance value ratio between the indoor oxygen concentration of 21% (during normal combustion) and 17% (during incomplete combustion). And detection sensitivity decreases exponentially with heating temperature. From the viewpoint of detection sensitivity, the lower the heating temperature of the element (S), the better.

Next, the opening degree of the damper (08) can be switched between two stages, and the normal combustion state and incomplete combustion state (C
The O concentration can be changed quickly between about 101,000 pp. At this time, time is determined until the resistance value of the element (S) decreases to a resistance value corresponding to a CO concentration of 500 ppm. This is shown as the response time in FIG. The response becomes exponentially faster with heating temperature. From the viewpoint of detection speed, it is preferable that the heating temperature of the element (S) is high.

In order to reduce the detection delay to incomplete combustion to 2 to 3 minutes or less, the heating temperature of the element (S) should be 140° C. or higher. Note that these conclusions have meaning regarding the specific material of the element body (S2).

Although the optimum heating temperature shifts when the material is changed, similar characteristics can still be obtained by shifting the temperature according to each material. The response speed in FIG. 10 is the response speed when incomplete combustion suddenly occurs. Normally, incomplete combustion gradually occurs as the indoor oxygen concentration decreases, so the response speed of the element (S) is improved more than it appears.

Another interesting point in FIG. 10 is that the temperature dependence of the resistance value of the element (S) during incomplete combustion is slightly positive. This property plays an important role in avoiding malfunctions during initial actions.

11th to 12th results for initial action
As shown in the figure. Figure 11 shows an element (S) that had been left at room temperature for 6 months (183 days), a cover (S 12) made of 20 meshes of double gold copper was attached, and a Bunsen burner (010) was ignited at time O. This figure shows the behavior at each steady-state heating temperature of the element (S). The vertical axis of the figure is the element (S
) and the resistance value (RsrD) at a CO concentration of 500 ppm.
The following malfunctions.

When the steady-state heating temperature of the element (S) is lowered, the peak of the output due to the [+] initial action becomes smaller, but (2) the period during which the initial action continues becomes longer.

That is, by lowering the heating temperature of the element (S), malfunctions due to initial actions can be prevented.

It should be noted that the time it takes for the output to reach its peak during the initial action is quite long, and even in the case of heating to 29°C, the time it takes to reach the peak is approximately 4 minutes. However, this is because the thermal time constant of the element (S) is as large as 64 seconds, so by removing the cover (512), the thermal time constant is reduced to 1.
When the time is set to about 0 seconds (dashed line in the figure), the output peaks at about 2 minutes.

FIG. 12 shows the relationship between the steady heating temperature (Ts) and the peak of the appearance at the time of initial action for each of the five elements (S) left for six months. The experimental method was the same as in the case of FIG. The vertical axis on the right side of the figure shows the maximum value of electrical conductivity of the element (S), and the vertical axis on the left side shows the minimum value of resistance value and Rsr.
The ratio with D (resistance value to 500 ppm of CO) is shown.

When the heating temperature (Ts) is lowered, the peak of electrical conductivity becomes smaller (2) Rs
rD becomes smaller.The two effects combine to reduce the possibility of malfunction.

For this element (S), malfunction due to initial action can be prevented by setting the steady heating temperature (Ts') to 200° C. or lower.

Table 2 shows the relationship between the output peak at the time of initial action (ratio of minimum resistance value R5 and resistance value R5TD with respect to CO500 ppm) and the standing period at room temperature.

Table 2 Idle period R5m1lv/R5TD R5m1n/R5
TD R3m11?5TD (day) (185℃)
(205°C) (250°C) 1 to 20 to 5 to 4 7 to 12 5 2.5 14 to 10 4 2.0 30,. 8 B 1.5 9062-1 18B 2 0.8 0°3 322 1.5 0.6 0.3 The degree of initial action increases with the standing period. The period of time that should be considered regarding the initial action is as follows: (1) In many cases, malfunctions due to the initial action can occur if the water heater is left unused for more than two weeks, so it is preferable to leave it for more than two weeks, and (2) about one month. (02) is often not used, so it is preferable to leave it for one month or more. (3) The longest possible period of leaving is usually 6 months without using the local boiler (02) from spring to autumn. In this case, 6 months is sufficient.

Note that the thermal time constant of the element (S) had almost no effect on the peak of the output at the time of the initial action.

The detection characteristics when the Bunsen burner (010) is incompletely burnt from the beginning will be examined with reference to FIGS. 13 and 14. In FIG. 13, the cover (512) of the element (S) in FIG. 3 is shown.
The temperature rise characteristics when only the mesh is deformed are shown. The figure shows the pilot burner (012) and Bunsen burner (
010) are applied almost simultaneously. Even with such an extremely rough cover (512), the heating temperature and time constant of the element (S) change. With other covers, such as covers made of sintered metal, the thermal time constant becomes extremely large. Table 3 shows the values of the steady-state heating temperature ('Ts) and thermal time constant of the element (S) based on FIG. 13.

Table 3 Cover mechanism Steady heating temperature Thermal time constant T s ('C: ) (Seconds) Without cover 2
83 11 20 210 64 40 207 90 60 ' 200 120 100 194 15,'0 A large thermal time constant delays the heating of the element (S) and causes a detection delay.

When heating the element (S) to 180℃±5℃, cover (
Table 4 shows the relationship between the mesh in S12) and the detection delay time. Please note that this element (S) has been in continuous use.
Initial action is small. The detection/delay here means that the resistance value of the element (S) after ignition is at the detection level (CO concentration 500 ppm) for the Bunsen burner (010), which is placed in a state where CO gas of about 11,000 ppm is generated from the beginning. corresponds to ).

Table 41 Mesh of cover Detection delay Thermal time constant (seconds) No cover 30 seconds 11 20 60 seconds 64 40 2 minutes 90 60 3 minutes 120 100 5 minutes 150 The detection delay increases with the thermal time constant, and the detection qh is reduced to 3
It can be seen that the thermal time constant must be 120 seconds or less in order to make it less than 1 minute.

Although the detection delay is shown here as an effect of the cover (512), this is due to the effect of the thermal time constant of the element (S) as an effect of the cover (S12).

For example, even if the thermal time constant is changed by increasing the heat conduction between the element body (S2) and the base (S8), almost the same detection delay will occur for the same thermal time constant.

Figure 14 shows the behavior of the initial action when combustion is incomplete from the beginning. The experimental method was the same as that in Table 4, except that the device (S) that had been left at room temperature for 6 months was used.

From the figure, it can be seen that (it) the element (S) is sensitive to CO gas even during the initial action process, and (2) the lower the heating temperature, the slower the detection.

In this case as well, the cover ('512) of the element (S) affects the detection time, and when heated to 180°C ± 5°C, the cover (S1
2) Without it, the time to detection is about 40 seconds, while with 20 mesh Kag-(512) it takes about 7 seconds.
0 seconds, 40 meshes takes 2 minutes and 30 seconds, 60 meshes takes about 3 minutes, and 100 meshes takes about 5 minutes.

Next, results related to pulse noise are shown in FIGS. 15 to 18. Figure 15 shows the gap of the element (S) < - (S12)
This shows the pulse noise output when 200 meshes. Here, the Bunsen no Kuna (010) is turned on and off in a cycle of 3 minutes on and 1 minute off. At that time, the applied voltage (VRL) to the load resistance (RL) and the element (S
) temperature (Ts') is shown.

As a result of the experiment, the things that govern the pulse noise output are (+) the steady heating temperature (Ts) of the element (S), and (2)
The cooling rate of the element (S) when extinguishing the Bunsen burner (010) was found to be two.

FIG. 16 shows the cooling characteristics of the element (S) after the Bunsen burner (010) is extinguished. It can be seen from the figure that the cooling rate of the element (S) varies greatly depending on the cover (S L2), that is, depending on the thermal time constant, and that the cooling rate corresponds well to the thermal time constant during temperature rise. The cooling rate can be determined based on the thermal time constant during temperature rise. Also, even if approximately 30 seconds have passed after extinguishing the Bunsen burner (010), 10
With a double gold steel cover (512) of 0 mesh (thermal time constant 150 seconds), the element (S) is only cooled by 30°C. The temperature of the element (S) at this time is 164° C., and the element (S) is maintained at a temperature at which it can be sensitive to CO.

The measurements shown in FIG. 16 were carried out simultaneously with the measurements shown in FIG. 13 and Table 3, and the steady heating temperature of each element (S) is shown in Table 3.

FIG. 17 shows the relationship between the cover (S12) of the element (S) and the pulse noise output at a steady heating temperature of 180° C.±5° C. The horizontal axis of the figure shows the time until re-ignition after extinguishing the Bunsen burner (010), and the vertical axis shows the ratio between R5TD and the minimum resistance value of the element (S) during pulse noise, and this ratio is 1 Malfunctions occur due to the above. From this result, (+) The element (S) cools down over time and the pulse noise output becomes smaller. (2) The smaller the thermal time constant, the smaller the pulse noise output. The thermal time constant is preferably 120 seconds or less. I know that I should.

FIG. 18 shows the relationship between the steady heating temperature (Ts) of the element (S) and the pulse noise output. The experimental method and the meanings of the axes in the diagram are exactly the same as in the case of FIG. 17. It can be seen from the figure that the lower the steady state heating temperature (Ts) of the element (S), the smaller the pulse noise output. This is because the lower the initial temperature, the lower the temperature of the element (S) at the time of pulse noise, and the delay in response to the co gas generated in pulses at the time of pulse noise. It can be seen that if the temperature of the element (S) is set to 200 DEG C. or lower, malfunctions due to pulse noise can be prevented except when the Bunsen burner (010) is turned on and off extremely frequently.

That is, preventing malfunctions caused by initial actions also has the effect of reducing malfunctions caused by pulse noise.

〔Effect of the invention〕

The invention of the present application solves practical problems in detecting incomplete combustion with a gas detection element using a gas-sensitive metal oxide semiconductor.

According to the first invention of the present application, an appropriate installation position of the gas detection element can be found, and malfunctions caused by initial actions can be prevented, and malfunctions caused by pulse noise can be reduced.

Next, in the second invention of the present application, in addition to the above effects, dead time can be shortened and malfunctions due to pulse noise can be further reduced.

In addition to the effects of the first invention, the third invention of the present application can eliminate malfunctions caused by pulse noise.

[Brief explanation of drawings]

Figure 1 is a partially cutaway front view of the embodiment, and Figure 2 is its
3 is a partially cutaway perspective view of a gas detection element, and FIG. 4 is a partially cutaway plan view of a modified gas detection element. FIG. 5(A) is a circuit diagram of the embodiment, and FIG. 5(B) is a circuit diagram of another modification. FIG. 6(A) is a circuit diagram of a modified example, and FIG. 6(B) is a sectional view of the main part of the device. FIG. 7 is a circuit diagram of still another modification. FIG. 8(A) is a circuit diagram of yet another modification, FIG. 8(B)
is a partial cutaway diagram of the main part. 9 to 18 are characteristic diagrams of the gas detection element, respectively. (02)・Water boiler, (04)・Solenoid valve, (010
)...Bunsen burner, (012)...pilot burner, (020)...fin, (lO) thermoelectric element, (S)
, (s')...Gas detection element, (RL,,)...Load resistance, (14)...Germanium transistor, Q8
), Nene, (+a) Capacitor, (4. Heat-sensitive element,
(28)・Photoconductive element, (T1)・・Mechanical timer. Patent applicant Figaro Giken Co., Ltd. No. 1 Fig. 9i2 Fig. 2 Fig. 3 Fig. 4 Fig. 5 (A) 121 Fig. 5 (B) Fig. 6 (B) 4 Fig. 6 (A) τ Fig. 7 figure! Figure 14 Figure 15 nme (min)

Claims (1)

[Claims] +1+ In a combustion device in which a burner and a heat exchanger heat a fluid together, a misfire in a burner is detected by a thermoelectric element, and a gas-sensitive metal oxide semiconductor is detected by exhaust gas from the burner. A gas detection element that uses a change in resistance value is heated to a temperature that allows detection of CO gas, and the electromotive force obtained from the thermoelectric element when the burner is ignited is used as a power source to detect incomplete combustion. In the device in which the safety means is activated during complete combustion, the gas detection element is installed at a position downstream of or inside the heat exchanger where ambient air does not enter, and the steady-state value of the heating temperature of the gas detection element is determined by A combustion safety device characterized in that the peak value of the output of a gas detection element left at room temperature at the time of burner ignition is set to a temperature below which the operating level of the safety means is reached. (2) The gas-sensitive metal oxide semiconductor has S n 0
2 and In20B, and the steady-state value of the heating temperature of the gas detection element is 120 to 80
The combustion safety device according to claim 1, characterized in that the temperature is within the range of 0°C. (3) The gas-sensitive metal oxide semiconductor has S n '0
2, and S n O2 contains Pt, Pd, Rh, and Ru. At least an element of the group consisting of Ir, Os, and Au is added, and the amount added is S n in terms of the additive metal.
o2. It is 0.1 to 5 parts by weight per 100 parts by weight, and the steady value of the heating temperature of the gas detection element is 120 to 250°.
Claim 2, characterized in that it falls within the scope of C.
Combustion safety device as described in section. (4) The additive element is Pd, and the amount added is 0 per 100 parts by weight of S n in terms of additive metal.
．． 4. The combustion safety device according to claim 3, wherein the amount is 5 to 2.0 parts by weight, and the steady-state heating temperature of the gas detection element is within the range of 140 to 210°C. (5) The period when the gas detection element is left at room temperature is short;
Claim 1 characterized in that both periods are two weeks.
Combustion safety device as described in section. (6) The combustion safety device according to claim 5, wherein the gas detection element is left at room temperature for at least one month. (7) The combustion safety device according to claim 6, wherein the gas detection element is left at room temperature for a period of six months or more. (8) In a combustion device that heats a fluid using a burner and a heat exchanger, a thermal lightning element detects a burner misfire, and detects a change in the resistance value of a gas-sensitive metal oxide semiconductor due to the exhaust gas from the burner. The gas detection element used is heated to a temperature that allows detection of brown CO gas, and when the burner is ignited, the electromotive force obtained from the thermal lightning element is used as a power source to detect incomplete combustion, ensuring safety in the event of a burner misfire or incomplete combustion. In the device in which the means is operated, the gas detection element is installed at a position downstream of or inside the heat exchanger where ambient air is not mixed in, and the steady value of the heating temperature of the gas detection element is left at room temperature. A combustion safety device, characterized in that the peak value of the output of the gas detection element at the time of burner ignition is below a temperature at which the operating level of the safety means is reached, and the thermal time constant of the gas detection element is 120 seconds or less. (9) The gas detection element includes a pair of electrode wires connected to a molded body of a gas-sensitive metal oxide semiconductor, the ends of the electrode wires being fixed to lead pins to support the molded body, and the molded body 9. The combustion safety device according to claim 8, wherein the lead pin is covered with a wire mesh having a coarseness of 60 mesh or more. (10) In a combustion equipment in which a burner and a heat exchanger heat a fluid together, a misfire in a burner is detected by a thermal lightning element, and the resistance value of a gas-sensitive metal oxide semiconductor is determined by exhaust gas from the burner. A gas detection element that uses CO gas is heated to a temperature that allows CO gas to be detected, and the electromotive force obtained from the thermoelectric element when the burner is ignited is used as a power source to detect incomplete combustion. In the device in which the safety means is activated, the gas detection element is installed downstream of or inside the heat exchanger at a position where ambient air is not mixed in, and the steady value of the heating temperature of the gas detection element is left at room temperature. The peak value of the output of the gas detection element when the burner is ignited is set to be below the temperature at which the safety means operates, and a pulse noise malfunction prevention means is provided that prohibits the operation of the safety means for a predetermined period after the burner ignites. A combustion safety device featuring: (11) The combustion safety device according to claim 10, wherein the predetermined period is 1 to 20 seconds.