JPS6223215B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion safety device for a combustor, and more specifically, the present invention relates to a combustion safety device for a combustor. The present invention relates to a combustion safety device for a combustor having a combustion region in which a burner is operated to burn while maintaining the amount of air at a relatively high value of 1 or more or around 1.

Conventionally, a combustion safety device is known in which a thermocouple is provided as a sensor for detecting oxygen-deficient combustion in a burner, and combustion in the burner is stopped based on a detection signal from the sensor. If the burner is operated at a relatively high value near 1, the output characteristics shown in Figure 4 are shown, and poor combustion in the burner is unlikely to occur when the oxygen concentration in the indoor air decreases. excess rate 0.7
If the setting is set in the region where Bunsen combustion occurs, a lift-up phenomenon due to oxygen deficiency will occur when the oxygen concentration decreases to 16-18%, but if the primary air excess ratio is
If it is set to about 0.9, the lift-up phenomenon will not occur unless the oxygen concentration drops to about 15% below the permissible level, which is accompanied by the inconvenience of delaying the combustion stop of the burner in the event of oxygen deficiency.

In order to eliminate such inconveniences, the present invention provides a device that reduces the primary air excess ratio intermittently to make it easier to cause poor combustion in the burner, and to stop combustion in the burner early when the oxygen concentration decreases. The present invention will be described below with reference to the illustrated embodiments.

Figures 1 and 2 show hot air gas heaters,
The inlet 1a and the outlet 1 are installed in the heater main body 1, which has an inlet 1a on the back and a warm air outlet 1b on the front.
An inner case 2 is provided which communicates with the inner case 2.
A blower 3 and a combustion case 4 above the blower are housed inside, and a pair of main and sub burners 5 and 6 are disposed inside the combustion case 4, and when the blower 3 operates, air flows into the room from the suction port 1a. At the same time as air is sucked in, hot combustion air is sucked and exhausted from the exhaust port 4a at the top of the combustion case 4, and both are mixed in the inner case 2 and blown out as warm air into the room from the blowout port 1b. At this time, the mixing tube end of each burner 5, 6 is heated by the suction force of the blower 3 acting on the inside of each burner 5, 6 through each flame hole in its combustion surface 5a, 6a. The primary air for combustion is forcibly supplied from the primary air holes 5b and 6b.

Referring to FIG.
The governor 9 is configured to supply gas to the main burner 5 via a temperature control solenoid valve 10, and the solenoid valve 10 is controlled by a signal from a temperature control circuit 11 to be described later. It is possible to freely switch between weak combustion, in which only the auxiliary burner 6 is operated by closing the solenoid valve 10, and strong combustion, in which both the main and auxiliary burners 5 and 6 are operated by opening the solenoid valve 10. At the same time, the rotation of the blower 3 is also controlled to be strong or weak.

Then, by appropriately setting the opening degree of each of the primary airs 5b and 6b, the primary air excess ratio is 1.2 in the main burner 5.
The temperature should be maintained at about 0.9 using the secondary burner 6. Here, the primary excess air ratio of the main burner 5 is set to 1
The purpose of setting the above value is to reduce the NOx concentration in the exhaust gas as known from JP-A-57-192740, and setting it to 0.9 for the auxiliary burner 6 prevents combustion from becoming unstable when switching the strength. This is to ensure that. That is, the suction force of the primary air by the blower 3 changes depending on the internal pressure of the combustion casing 4, and when switching from weak to strong, the internal pressure of the combustion casing 4 increases from the level during weak combustion to the level during strong combustion. In the transient state up to this point, the excessive suction force caused by the strong rotation of the blower 3 caused the sub-burner 6 to
When switching from strong to weak, the primary excess air ratio temporarily increases due to the The primary air excess ratio is 0.5 to 0.5, which is necessary for stable combustion.
In order to keep it within the range of 1.4, we have estimated this increase/decrease range in advance and set it to about 0.9, which is in the middle.

FIG. 3 shows a control circuit including the temperature control circuit 11 described above, and the temperature control circuit 11 is connected to the main switch 1.
2 is connected to the output side of a constant voltage circuit 13 that is energized when the circuit 2 is closed, and a high-level strong combustion signal and a low-level weak combustion signal are output to the first output terminal 11a according to the deviation between the room temperature and the set temperature. A first relay _R1 for controlling the opening and closing of the temperature control solenoid valve 10, and a second relay _R2 for controlling the rotation of the blower 3.
The first output terminal 11a is connected to the base of a first transistor 14 which is commonly inserted in the current-carrying circuit with the first transistor 14, and when the strong combustion signal is output, the first transistor 14 is turned on and the first transistor 14 is turned on. Relay R ₁ , R ₂
is energized, and the relay switch r ₁ of the first relay R ₁ is energized.
is turned on and the solenoid valve 10 is opened, and
The relay switch _R2 of the second relay _R2 is switched to the strong rotation terminal a side of the drive motor 3a of the blower 3, and the blower 3 is rotated strongly, and according to the output of the weak combustion signal, the first transistor 14 is turned off, the energization of the first and second relays R ₁ and R ₂ is stopped, relay switch r ₁ is turned off and the solenoid valve 10 is closed, and relay switch r ₂ is moved to the weak rotation terminal b side. The switch was made so that the blower 3 was rotated at a low speed. In the drawing, reference numeral 15 indicates a fan switch which is closed in conjunction with the main switch 12, and reference numeral 16 indicates a bimetal switch parallel to this.

In addition, in the drawing, 17 and 18 indicate thermocouples which are defective combustion detection sensors provided facing the main burner 5 and the auxiliary burner 6. During strong combustion, the first thermocouple 17 facing the main burner 5 is used. and the second one facing the sub-burner 6.
When the electromotive force of any of the thermocouples 18 drops below the reference level, or during weak combustion, the first thermocouple 17
Regardless of the electromotive voltage of the second thermocouple 18, each electromagnetic safety valve 7 is closed when the electromotive voltage of the second thermocouple 18 falls below a reference level. To explain this in more detail, the electromotive force of the first and second thermocouples 17 and 18 is transmitted to the first comparator 21 for the first thermocouple 17 and the second thermocouple through amplifier circuits 19 and 20, respectively. 18 and the second comparator 22 for safety valve 7.
is the second transistor 2 in series with the solenoid.
The third transistor 25 on the input side of the comparator 24 that turns on and off the second transistor 23 is turned off, and the output from the comparator 24 becomes low level, so that the second transistor 23
The output terminal of the second comparator 22 is connected to the voltage application circuit 26 connected to the base of the third transistor 25, and the strong combustion signal from the temperature control circuit 11 is connected to the voltage application circuit 26 connected to the base of the third transistor 25. The output terminal of the first comparator 21 is connected to the output terminal of the first comparator 21 through the fourth transistor 27, which is turned on at First and second thermocouples 17, 18
When the electromotive voltage of any one of them falls below the reference value and correspondingly, the output of either of the first and second comparators 21, 22 becomes low level, the voltage application circuit 26 is grounded via its internal circuit. and the third transistor 2
5 is turned off and the electromagnetic safety valve 7 is closed, and during weak combustion, the fourth transistor 27 is turned off and the second
The third transistor 25 is controlled to be on/off only by the comparator 22, and when its output becomes low level, the electromagnetic safety valve 7 is closed.

Combustion safety measures are taken with the above configuration, but
When the primary excess air ratio is set to a value of 1 or more or a value close to 1, such as 0.9, as described above, poor combustion is less likely to occur even when the oxygen concentration in the indoor air decreases, and if left as it is, the oxygen concentration will not reach the allowable level. It becomes difficult to stop combustion before the temperature drops below.

Therefore, in the present invention, in the region where the primary air excess ratio is maintained at a relatively high value as described above and combustion is performed, the primary air excess ratio is intermittently reduced during the combustion operation to prevent poor combustion in the case of oxygen deficiency. Bunsen combustion, which is likely to occur, is caused to occur, so that combustion can be stopped early.

As a method to reduce the primary excess air ratio, 1
There are two methods: increasing the gas amount without changing the primary air supply amount, and decreasing the primary air supply amount without changing the gas amount. 3 was intermittently rotated weakly to reduce the amount of primary air supplied, so that the excess primary air ratio in the auxiliary burner 6 was intermittently reduced from about 0.9 to about 0.7.

At this time, the primary excess air ratio of the main burner 6 is also 1.2.
However, at this level, poor combustion will not occur unless the oxygen concentration falls below 15%, and the secondary burner 6 will function effectively as a countermeasure against oxygen deficiency.
It is.

The intermittent switching of the blower 3 to low rotation is controlled by the interval timer circuit 28.
To explain this in detail, the timer circuit 28 is operated by the ignition signal of the main burner 5 outputted to the second output terminal 11b of the temperature control circuit 11, and a timer IC 29 counts the number of oscillations of the built-in oscillation circuit. and a CR circuit for setting the oscillation period,
The timer IC 29 is connected to the energizing circuit of the second relay _R2 .
A fifth transistor 30 whose base is connected to the output terminal 29a of the CR circuit is connected to the capacitor 3.
1 and a first and second resistor 3 connected thereto in parallel with each other.
2 and 33, the second resistor 33 is connected to the collector side of the fifth transistor 30 via a diode 34, and according to the high level output from the output terminal 29a, the fifth transistor 30 is turned on, the second relay _R2 is energized via the fifth transistor 30 and the first transistor 14, and the blower 3 is strongly rotated. 30,
The oscillation period by the CR circuit is set to a relatively long period determined by the capacitor 31 and the first resistor 32, and after counting a certain number of times, for example 15 minutes, the output terminal 29a According to this low level output, the fifth transistor 30 is turned off and the second relay _R2 is stopped energizing, and the blower 3 is switched to low rotation. The oscillation period is determined by the capacitor 31 and the first and second resistors 32 and 33.
The time required to count a certain number of times is shortened to, for example, 1.5 minutes, and after 1.5 minutes, the output of the output terminal 29a is switched to high level again, and the above operation is thereafter performed. By repeating this, blower 3 was switched to low rotation for 1.5 minutes every 15 minutes.

Therefore, when the blower 3 is switched from strong rotation to weak rotation, the primary air excess ratio of the auxiliary burner 6 is reduced from 0.9 to, for example, about 0.7, and in this state, even if the oxygen concentration does not fall below 15%, If it has fallen to 16-18%, defective combustion occurs in the auxiliary burner 6, which is detected by the second thermocouple 18, and the electromagnetic safety valve 7 is closed to stop combustion.

In the illustrated example, the primary air excess ratio of the auxiliary burner 6 is maintained at a relatively high value of about 0.8 to 0.9 even during weak combustion. The rotation may be further reduced to intermittently reduce the primary excess air ratio, but when the combustion amount of the sub-burner 6 is small, there is no need to take special measures against oxygen deficiency in relation to the ventilation rate of the room. Therefore, in the illustrated embodiment, the blower 3 is intermittently switched to low rotation only during strong combustion.

As described above, according to the present invention, Bunsen combustion is performed by intermittently decreasing the primary air excess ratio during combustion operation while maintaining the primary air excess ratio at a relatively high value of 1 or more or around 1. If the oxygen concentration is low, poor combustion will occur in the Bunsen combustor, and the thermocouple output will rapidly decrease and reach below a certain standard. It has a safe effect.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional side view of an example of a combustor to which the present invention is applied, Fig. 2 is a front view cut along the - line in Fig. 1, Fig. 3 is a line diagram showing its control circuit, and Fig. 4 is a cross-sectional side view of an example of a combustor to which the present invention is applied. FIG. 3 is a diagram showing the output characteristics of a thermocouple. 5, 6... Burner, 17, 18... Thermocouple (sensor).

Claims (1)

[Claims] 1 Forcibly supply primary air for combustion to the burner 1
The combustor is a combustor that has a combustion region in which the burner is operated for combustion while maintaining the excess air ratio at a relatively high value of 1 or more or around 1, and is equipped with a thermocouple as a sensor for detecting poor combustion in the burner. In a device in which combustion is stopped when the output of the burner decreases below a certain reference value, the primary air excess ratio is intermittently reduced during the combustion operation of the burner to perform Bunsen combustion. A combustion safety device for a combustor featuring: