JPS6319718Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion control device for a gas appliance that uses a flame rod to detect a burner misfire.

Conventionally, this type of device is equipped with a comparator that inputs the detected voltage from the flame rod that changes depending on the magnitude of the resistance value between the burner and the flame rod, and the comparator is used to input the detected voltage from the flame rod that changes depending on the magnitude of the resistance value between the burner and the flame rod. By applying a set voltage according to the upper limit value, the ignition device, electromagnetic safety valve, or other safety means to be operated in the misfire state of the burner is set to the voltage generated by the comparator when the resistance value is larger than the upper limit value. There are known devices that are activated by output.

However, according to this method, if a short circuit occurs between the burner and the flame rod for some reason during ignition operation or during operation, the resistance value between the burner and the flame rod will change regardless of whether there is a flame in the burner or not. This has the disadvantage that it is maintained at a small value and does not provide activation of safety measures in the event of a misfire.

The purpose of the present invention is to provide a device that eliminates the above-mentioned disadvantages. 1 comparator 2, applying a first set voltage corresponding to the upper limit value of the resistance value at the time of ignition of the burner to the first comparator 2, and operating in a misfired state of the burner; A second comparator into which the detected voltage is input, in which the electromagnetic safety valve or other safety means 3 is actuated by the output generated from the first comparator 2 when the resistance value is larger than the upper limit value. 4 is provided, and a second set voltage corresponding to the lower limit value of the resistance value at the time of ignition of the burner is applied to the second comparator 4, and the safety means 3 is set such that the resistance value is smaller than the lower limit value. In this case, it is also activated by the output generated from the second comparator 4.

The first comparator 2 has a first set voltage applied to its positive input terminal, and a detection voltage from the flame rod 1 which increases in proportion to the resistance value between the burner and the flame rod 1 to its negative input terminal. Ru. As the first set voltage, use a voltage corresponding to the upper limit value (several tens of MΩ) of the resistance value between the burner and the flame rod 1 when there is a flame between them, and when the detected voltage is higher than that, is from the first comparator 2 assuming that the burner is in a misfire state.
A LOW level output signal is now generated.

The second comparator 4 has its positive input terminal applied with the detection voltage from the frame rod 1, and its negative input terminal applied with the second set voltage. As the second set voltage, use a voltage corresponding to the lower limit value (several MΩ) of the resistance value between the burner and the flame rod 1 when there is a flame between them, and when the detected voltage is lower than that. is a LOW signal from the second comparator 4 assuming that the frame rod 1 is short-circuited.
A level output signal is now generated.

The illustrated one uses an ignition device as the above-mentioned safety means 3, and its operating circuit is composed of a relay 6 with a normally closed relay contact 6a interposed in the energizing circuit 5 of the ignition device, and a first comparator 2. a first NPN transistor 7 whose base is connected to the output terminal of the second comparator 4; and a second NPN transistor whose base is connected to the output terminal of the second comparator 4.
It is composed of a series connection circuit of transistors 8, and when a LOW level output signal is generated from the first comparator 2 or the second comparator 4 and the first NPN transistor 7 or the second NPN transistor 8 is non-conductive, the relay 6 was deactivated, and the igniter was energized to generate electric discharge and ignite the burner.

In addition, when an electromagnetic safety valve is used as the above-mentioned safety means 3, a normally open relay contact shall be inserted in the energizing circuit 5, and as in the case of the above-mentioned ignition device, either the comparator 2 or 4 will release the LOW signal. When a level output signal is generated and one of the transistors 7 and 8 becomes non-conductive, the relay 6 is deactivated and the safety valve is activated to close, thereby cutting off the gas supply to the gas appliance. Do it like this.

Next, we will explain the case where the ignition device is used as the safety measure 3. When the burner is in a normal combustion state and there is a flame between the burner and the flame rod 1, the resistance between them is several MΩ.
.about.several tens of MΩ, and the first and second comparators 2 and 4 both generate high level output signals, so the ignition device is in an inactive state and no discharge occurs.

At this time, if the burner and the flame rod 1 are short-circuited for some reason, the first comparator 2
A high level output signal is generated from the first comparator 2, and therefore, in a conventional type that does not have any comparator other than the first comparator 2, the ignition device will fail to operate, causing the discharge of raw gas, which is dangerous. However, according to the present invention, a second comparator 4 is provided in addition to the first comparator 2, and when the burner and the flame rod 1 are short-circuited, a detection voltage significantly lower than the second set voltage is applied from the flame rod 1 to the positive input terminal of the second comparator 4, resulting in a low level output signal from the second comparator 4.
Since the 2NPN transistor 7 is not conductive, the relay 6 is not energized, its contacts are maintained in a closed state, the ignition device operates reliably, and the burner can be immediately restored to a normal combustion state.

In addition, if the burner and flame rod 1 are short-circuited during ignition operation, the high level generated from the first comparator 2 is The ignition device will not operate from the beginning due to the output signal of , and raw gas will be released, which is dangerous. However, according to the present invention, in the above case where the burner and flame rod 1 are short-circuited when the burner is in a normal combustion state, Similarly, since a LOW level output signal is generated from the second comparator 4,
The ignition system operates reliably and is safe.

In this way, according to the present invention, the short circuit between the burner and the flame rod 1 is detected by the second comparator 4, and the detection signal is used to activate the safety means 3, so that the release of raw gas is reliably prevented. It has a safe effect.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing one example of implementation of the present invention. 1...Frame rod, 2...First comparator, 3
...Safety means, 4...Second comparator.

Claims (1)

[Scope of utility model registration request] A first comparator 2 is provided which inputs the detected voltage from the flame rod 1 which changes depending on the magnitude of the resistance value between the burner and the flame rod 1, and the first comparator 2 is connected to the resistance value when the burner is ignited. By applying a first set voltage corresponding to the upper limit value of the resistance value, the ignition device, electromagnetic safety valve, or other safety means 3 to be operated in the misfire state of the burner is set to the first set voltage when the resistance value is larger than the upper limit value. A second comparator 4 is provided to input the detected voltage, and the lower limit of the resistance value at the time of ignition of the burner is set in the second comparator 4. A second set voltage corresponding to the resistance value is applied, and the safety means 3 is also activated by the output generated from the second comparator 4 when the resistance value is smaller than the lower limit value. Combustion control device for gas appliances.