JPS618518A - Burning safety device - Google Patents

Abstract

PURPOSE:To enable the detection of oxygen deficiency by a flame rod in a full primary air type burner by a method wherein a solenoid valve is operated to be closed when the difference between a memory output valve by a comparison circuit and a stationary output value is less than zero. CONSTITUTION:A flame rod 3 is provided as a flame detecting element above a flame hole 1 of a full primary air type burner 2 having a gauze for the flame hole 1. A memory circuit 4 stores the output value from the flame rod 3, a comparison circuit 5 is provided for comparing the output value obtained constantly from the flame rod with the flame rod output value of the memory circuit 4. When the value of the comparison circuit 5 is less than zero, a solenoid valve 6 is closed by a driving circuit 7. In case that the equivalance value a1 of a mixing gas is set less than zero, when the equivalance ratio becomes a2 exceeding one after an oxygen concentration is decreased due to the long operation time, the Bunsen flame is formed after changed from the full primary surface flame. At this time, the difference between the stored flame electric current value a1 and the stationary output a2 is indicated as a minus value, accordingly, the maintaining of full primary surface burning is judged as difficult, the solenoid valve 6 is closed by the driving circuit 7, therefore, the safety of burning can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a technique for preventing incomplete combustion in an all-primary air combustion apparatus using a flame detection element.

Conventional configuration and its problems An example of a combustion safety device using a flame detection element for an all-primary air type combustion device is disclosed in Japanese Patent Application Laid-open No. 129116/1983. This consists of a main burner and a pilot burner as an all-primary air type gas burner that burns air from a combustion blower as primary air, and each combustion surface has a separate flame lot t"1m, The flame current value of the main burner and the flame current value of the pilot burner are detected, and these flame current values are respectively input to a comparator via a current-voltage converter and an amplifier, and the output of this comparator is used to control combustion. The amplification factor of the amplifier is set in accordance with the change characteristics of the flame current value during weak combustion, and intermittent switching to weak operation during strong operation is provided.This invention Now, when detecting oxygen deficiency, a pilot burner is always required to compare the potential difference between the main burner and the pilot burner.
Configuration and control become complicated. Furthermore, oxygen deficiency detection during strong combustion requires a forced switch to weak combustion, and is performed independently of indoor temperature adjustment, which poses problems such as poor usability. Furthermore, in the case of gases with a high combustion rate, the potential difference between the main burner and the pilot burner has little variation, making it difficult to detect oxygen deficiency.

OBJECTS OF THE INVENTION The present invention solves these conventional problems, and aims to provide a technique for preventing incomplete combustion using only the main burner by using a flame detection element for all primary combustion devices.

Structure of the Invention In order to achieve this object, the present invention includes an all-primary air burner, a flame detection element facing the flame hole surface of the burner, and a memory circuit for storing an output value from the flame detection element. A comparison circuit is provided for comparing the output value of the flame detection element obtained on a steady basis with the output value of the flame detection element stored in the memory circuit, and the comparison circuit compares the output value stored by the comparison circuit with the steady output value. A drive circuit is provided that drives the solenoid valve to close when the difference becomes zero or less.

In the case where a flame detection element and a typical flame rod are used, the relationship between the flame current value and the equivalence ratio will be briefly described using FIG. 2.

The horizontal axis shows the equivalence ratio χ, and the vertical axis shows the flame current value I. When the equivalence ratio is around 1, the flame current value If
has a convex relationship with the highest value.

Similarly to FIG. 2, FIG. 3 also shows the equivalence ratio on the horizontal axis and the flame current value on the vertical axis. According to the above configuration, when a flame rod is used as a flame detection element and the equivalence ratio is set to 1 or less as shown in al, the indoor oxygen concentration decreases according to the operating time, so that the oxygen concentration is substantially reduced up to a certain oxygen concentration. Generally speaking, the equivalence ratio will not increase, but the flame current value will increase. Therefore, since the difference between the flame current value a1 stored when the equivalence ratio is set at al and the steady output value a3 shows a positive value, it is considered normal combustion, and combustion continues. However, when the operating time becomes long and the oxygen concentration drops significantly, and the equivalence ratio exceeds 1 and reaches a3, the total primary combustion is not maintained.
A Bunsen flame will now form. At this time, since the difference between the steady output value a3 and the stored flame current value 83 shows a negative value, it is regarded as abnormal combustion, and the stain magnetic valve is closed by the drive circuit, and combustion is stopped. . On the other hand, when the equivalence ratio exceeds 1 at the start of operation, this corresponds to a bl state, that is, a primary air shortage due to restarting immediately after oxygen starvation or damper blockage, etc. In this case, the equivalence ratio increases with operation time and the flame current Since the value b2 decreases, the steady output value b2
Since the difference between the stored flame current value b1 and the stored flame current value b1 takes a negative value, combustion stops instantaneously. In this way, not only oxygen deficiency from all primary combustion states where the equivalence ratio is 1 or less, but also
Oxygen deficiency can also be detected in a high primary combustion state where the equivalence ratio is 1 or more.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. A frame rod 3 is provided above the flame hole 1 of the all-primary air burner 2 whose flame hole 1 is made of wire mesh.
a memory circuit 4 that stores the output value from the frame rod, a comparison circuit 5 that compares the output value from the frame rod that is constantly obtained with the output value of the frame rod stored in the memory circuit 4, and a solenoid valve 6. The drive circuit 7 is configured to close the solenoid valve 6 if the value of the comparison circuit 5 is less than zero, and the blower 8 is configured to close the solenoid valve 6.
It is located below.

According to the above configuration, the equivalence ratio of the air-fuel mixture is set to al in FIG.
As shown in Figure 2, when set to 1 or less, the indoor oxygen concentration decreases depending on the operating time, so the equivalence ratio substantially increases up to a certain oxygen concentration, that is, until the equivalence ratio approaches 1, and the flame current increases. The value also increases. However, the equivalence ratio is 8
Frame current value a1 stored when set at 1
Since the difference between the flame current value a2 and the constant output flame current value a2 shows a positive value, it is determined that full primary surface combustion is being performed, and combustion is continued. However, as the operating time became longer, the oxygen concentration decreased significantly, and the equivalence ratio exceeded 1.
When a2 is reached, all primary surface bumps fail and a Bunsen flame is formed. Since the difference between the flame current value a1 stored at this time and the steady output value a3 shows a negative value, it is determined that the combustion state is such that the total primary surface combustion is not maintained, and the drive circuit causes stains on the solenoid valve. is closed and combustion safety is ensured.

On the other hand, when the equivalence ratio during operation exceeds 1, this corresponds to a BL state, specifically, a primary air shortage due to restarting immediately after oxygen starvation or blockage of the damper, etc. In this case, the equivalence ratio increases as the operation time increases. Since the flame current value b2 continues to decrease, the flame current value b1 stored as the steady output value b2
Since the difference between the two values is a negative value, the combustion immediately stops from the above process.

In this way, by comparing the magnitude relationship between the flame current value at the beginning of operation and the flame current value during operation, the equivalence ratio of the air-fuel mixture at that time of operation can be determined, and this can be used to determine the oxygen concentration in the chamber. can be estimated and combustion can be controlled.

Effects of the invention (1) The magnitude relationship between the flame current value at the beginning of operation and the flame current value during operation is constantly compared and it is determined whether the light amount ratio exceeds 1, so complete primary combustion is guaranteed. At the same time, oxygen deficiency can be detected based on the flame current value even in all primary air burners.

@) In principle, changes in the equivalence ratio can be detected indirectly, so incomplete combustion due to insufficient primary air volume, such as damper blockage, can be detected.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a combustion safety device that is an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the relationship between the equivalence ratio and the flame current value, and Fig. 3 is the equivalence ratio and flame current in the device of the present invention. It is a characteristic diagram of values. 1...flame hole, 2...all primary air burner, 3...flame detection element, 4...memory circuit, 5... ... Comparison circuit, 6 ... Solenoid valve, 7 ... Drive circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3: f no φ

Claims (1)

[Claims] an all-primary air burner, a flame detection element facing the flame hole surface of the burner, a memory circuit that stores an output value from the flame detection element, and an output value of the flame detection element that is constantly obtained. and a comparison circuit that compares the output value of the flame detection element stored in the storage circuit, and when the difference between the output value stored by the comparison circuit and the steady output value becomes zero or less, the electromagnetic A combustion safety device with a drive circuit that drives the valve to close.