JPH0623609B2 - Combustion safety device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a combustion safety device for a gas heater and other gas combustion appliances.

(Prior Art) As a conventional device of this kind, a gas combustion appliance is provided with a detection element for detecting combustion failure of the burner, and when the detection output from the detection element falls below a predetermined judgment reference value, the burner is connected to the burner. It is known to stop the supply of gas to prevent combustion failure.

(Problems to be Solved by the Invention) When a thermocouple, for example, is used as the detection element, as shown in FIG. 1, the electromotive force of the thermocouple differs depending on the amount of combustion even if the oxygen concentration is the same. Further, as shown in FIG. 5, when the gas type is different, the degree of decrease in the electromotive force of the thermocouple with respect to the decrease in oxygen concentration is different.

However, according to the above-mentioned conventional device, the criterion value for stopping the supply of gas to the burner is constant regardless of the combustion amount or gas type of the gas combustion appliance, and therefore the burner is determined depending on the combustion amount or gas type. There is a disadvantage that the oxygen concentration is different when the gas supply is stopped.

According to Japanese Patent Laid-Open No. 62-91720, a plurality of determination reference values according to the combustion amount are stored in a ROM (read only memory) in advance, and the RO is appropriately set according to the combustion amount.
It is known that the determination reference value is called from M and the determination reference value is changed according to the increase or decrease of the combustion amount. In this one, the determination reference value according to the number of switching stages of the combustion amount is changed. It must be stored in ROM, and when applied to a combustor in which the combustion amount can be continuously switched, the number of judgment reference values to be stored becomes enormous, and it also corresponds to the change of gas type. However, since a judgment reference value must be set for each gas type, there is a problem in that a large capacity ROM must be used.

(Means for Solving the Problem) The present invention was devised to solve the above-mentioned inconvenience, and a gas combustion instrument in which the combustion amount can be freely changed by an electromagnetic proportional valve provided in the middle of the gas supply path. A detection element for detecting the combustion state of the burner is provided, and when the detection signal from the detection element falls below a predetermined determination reference value, the gas supply to the burner is stopped, and the determination reference value is set. A voltage dividing circuit is provided, and one of the voltage dividing resistance values of the voltage dividing circuit can be freely changed according to the gas type by operating the changeover switch. At the voltage dividing point of the voltage dividing circuit, a control signal to the electromagnetic proportional valve is provided. It is characterized by branching and inputting.

(Operation) Generate a judgment reference value according to the gas type by the voltage dividing circuit,
By arranging the judgment reference value to be changed by the control signal to the branched electromagnetic proportional valve, the judgment reference value can be changed according to the combustion amount and the gas type without providing a ROM or the like.

(Example) Next, the Example of this invention is described based on drawing.

FIG. 2 shows a circuit diagram of a combustion safety device. 1 is a burner of a gas combustion appliance, 2 and 3 are electromagnetic safety valves and electromagnetic proportional valves provided in a gas supply passage 4 to the burner 1, 5 Is a drive circuit for the solenoid proportional valve 3, and 6 is a proportional valve control circuit in which the output signal is variable due to the difference between the resistance value of a setter (not shown) and the room temperature. When the burner in which the solenoid safety valve 2 is open burns , The amplifier 7 by the control signal from the proportional valve control circuit 6
The collector current of the transistor 9 of the drive circuit 5 is controlled via 8 to control the current of the exciting coil 3a of the solenoid proportional valve 3 and the opening of the solenoid proportional valve 3 to control the burner. The combustion amount of 1 was controlled.

Reference numeral 10 is a thermocouple which is a detection element for detecting the combustion state exposed to the burner 1. The electromotive force from the thermocouple 10 is amplified to a predetermined level by an amplifier 16 and then one of the comparators 14 in the comparison circuit 11 is operated. Input to the terminal. On the other hand, in the comparison circuit 11, there is provided a voltage dividing circuit composed of the voltage dividing resistors 12a and 12b and the voltage dividing resistor 13 which are selectively switched by the change-over switch 22, and the control signal output from the amplifier 7 is supplied. It is connected via a resistor 19 so as to be branched to a voltage dividing point A of the voltage dividing circuit. Therefore, the changeover switch 22 is selected depending on the gas type.
Is switched to either of the voltage dividing resistors 12a and 12b, the potential of the voltage dividing point A, which is determined by the voltage dividing resistances 12a and 12b, changes according to the voltage change of the output part of the amplifier 7. And this partial pressure point A
Is connected to the other terminal of the comparator 14, and when the potential of one terminal to which the signal from the thermocouple 10 is input falls below the potential of the voltage dividing point A that changes with the control signal, the comparator 14 The combustion control circuit 15 is configured to output a signal, and the combustion control circuit 15 includes a comparator 14
When the signal from the electromagnetic safety valve 2 is received, the electromagnetic safety valve 2 is closed.

More specifically explaining this, the setter is operated to change the control signal from the proportional valve control circuit 6, and for example, the current of the exciting coil 3a of the electromagnetic proportional valve 3 is increased to increase the burner 1.
When the combustion amount of is increased, the voltage at the voltage dividing point A corresponding to the determination reference value is increased as shown in FIG. 3, and the current of the exciting coil 3a is decreased to decrease the combustion amount of the burner 1. When this is done, the voltage at the voltage dividing point A becomes small. That is,
In FIG. 4, when the magnitude of the combustion amount indicated by the solid line decreases, the voltage at the partial pressure point A, which is the judgment reference value indicated by the chain double-dashed line, also decreases, whereby the burner is kept at substantially the same oxygen concentration. Combustion of 1 can be stopped.

If the gas type is different, it is possible to obtain the determination reference value according to the gas type simply by switching the changeover switch 22.
In the figure, 17,18,20,21 indicate resistance.

(Effect of the invention) A judgment reference value corresponding to a gas type is generated by a voltage dividing circuit,
With a simple configuration that changes the judgment reference value by the control signal to the branched solenoid proportional valve, the oxygen concentration of the combustion air became a certain value or less without being affected by the size of the combustion amount and the type of gas. At that point, the burner can be deactivated.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the relationship between the electromotive force of a conventional thermocouple, the oxygen concentration and the generation of CO, FIG. 2 is a circuit diagram showing an example of the embodiment of the present invention, and FIG. 3 is an electromagnetic proportional valve. For explaining the relationship between the combustion amount and the judgment reference value that correlate with the current value of FIG. 4, FIG. 4 is a diagram showing the judgment reference value with a two-dot chain line in the relationship between the electromotive force of the thermocouple and the oxygen concentration, FIG. 5 is a diagram illustrating the relationship between the electromotive force of the thermocouple, the oxygen concentration, and the generation of CO when the gas species are different. 1 ... Burner, 3 ... Electromagnetic proportional valve 4 ... Gas supply path, 10 ... Thermocouple (detection element) 22 ... Changeover switch 12a, 12b, 13 ... Dividing resistance

Claims (1)

[Claims] 1. A gas combustion instrument having an electromagnetic proportional valve provided in the middle of a gas supply passage, the amount of combustion of which can be changed, is provided with a detection element for detecting the combustion state of the burner, and a detection signal from the detection element is transmitted. In a case where the supply of gas to the burner is stopped when the value falls below a predetermined judgment reference value, a voltage dividing circuit for setting the judgment reference value is provided, and one of the voltage dividing resistance values of the voltage dividing circuit of the changeover switch is set. A combustion safety device characterized in that it can be switched according to a gas type by an operation, and a control signal to an electromagnetic proportional valve is branched and input to a pressure dividing point of the voltage dividing circuit.