JPH0328658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a combustion safety device using a CO sensor or other incomplete combustion detection element.

(Prior Art) The applicant of the present application has previously proposed an electromagnetic safety valve as a device of this type, which is interposed in a fuel supply path to a burner, and a drive circuit for the electromagnetic safety valve that connects an operating solenoid of the electromagnetic safety valve to a thermoelectric element. placed in the combustion exhaust
The proposed system includes an incomplete combustion detection circuit that closes the electromagnetic safety valve when a gas concentration higher than a set value is detected by a CO sensor or other incomplete combustion detection element.

(Problem to be Solved by the Invention) The above method is convenient because it can correctly detect a predetermined incomplete combustion state when the temperature of combustion exhaust gas is within the normal temperature range, but for example, when the combustion exhaust gas is supplied to a burner, When the pressure of the gas increases and over-input occurs, and the temperature of the combustion exhaust rises outside the normal temperature range, a predetermined incomplete combustion state cannot be detected correctly.

This inconvenience is caused by the fact that when a CO sensor is used as the incomplete combustion detection element, as shown in Figure 2, the resistance value of the CO sensor at a predetermined incomplete combustion, for example when the CO concentration is 500 PPM, is It was found that this occurs because the temperature of the exhaust gas changes to about 180Ω when heated to 100℃, and to about 330Ω when heated to 150℃.

Therefore, in order to eliminate this inconvenience, it may be possible to provide a temperature compensation circuit that can correctly detect a predetermined incomplete combustion state even if the temperature of the combustion exhaust changes outside the normal temperature range. For example, there are inconveniences such as difficulty in adjusting the temperature.
Undesirable.

(Means for Solving the Problems) In view of the above, the present invention provides that, instead of providing a temperature compensation circuit, when the temperature of combustion exhaust gas falls outside the normal temperature range, this is regarded as an abnormality and a failure occurs. The present invention aims to provide a device in which an electromagnetic safety valve is closed by a complete combustion detection circuit, and the electromagnetic safety valve is interposed in the fuel supply path to the burner, and the operating solenoid of the electromagnetic safety valve is replaced with a thermoelectric element. A connected drive circuit for the electromagnetic safety valve and an incomplete combustion detection circuit that closes the electromagnetic safety valve when a gas concentration higher than a set value is detected by a CO sensor or other incomplete combustion detection element heated by combustion exhaust. A temperature switch that closes within a combustion exhaust temperature range in which the resistance value of the incomplete combustion detection element is held substantially constant during a predetermined incomplete combustion is connected to the incomplete combustion detection circuit. It is characterized by

(Function) According to the above configuration, when the temperature of the combustion exhaust falls outside the normal temperature range, the temperature switch opens, and the same occurs when the incomplete combustion detection element detects a gas concentration higher than the set value. Then, the electromagnetic safety valve is closed by the incomplete combustion detection circuit, and combustion of the burner is stopped.

(Example) Next, the present invention will be explained based on the illustrated example.

In FIG. 1, 1 indicates an electromagnetic safety valve interposed in a gas supply path 3 which is a fuel supply path to a burner 2, and 4 indicates a thermocouple which is a thermoelectric element facing the burner 2.
The operating solenoid 1a of the safety valve 1 and the thermocouple 4 are connected via the contact 5a of the latching relay 5 to form a drive circuit 6 for the safety valve 1, in other words, a safety circuit in the event of a misfire in the burner 2. .

The latching relay 5 includes a set relay 7, a reset relay 8, and a small capacitor 9,
When the capacitor 9 is charged, the set relay 7 is energized by the charging current to close the contact 5a, and the capacitor 9
When the potential of the reset relay 8 drops to approximately zero potential, the reset relay 8 is energized and the contact 5a is opened.

The latching relay 5 and an incomplete combustion detection circuit 10 for detecting gas concentration were connected to the battery 12 via a main switch 11 that opened and closed in conjunction with the burner 2 and extinguishing operation.

The incomplete combustion detection circuit 10 connects a voltage divider 15 consisting of a series connection circuit of a CO sensor 13 as an incomplete combustion detection element and a variable resistor 14 to the battery 12 via the main switch 11. 1
The voltage dividing point D of the latching relay 5 is connected to both bases of two PNP type transistors 17 and 18 connected in series through a diode 16, and the voltage dividing point D of the latching relay 5 is connected to the connection point C between the collector of the transistor 18 and the resistor 19. is connected to the capacitor 9 of the transistor 17.
The emitter is connected to the CO sensor 13.

Here, in the present invention, the CO sensor 13 of the incomplete combustion detection circuit 10 and the latching relay 5 are further provided.
A temperature switch 2 that closes within a combustion exhaust temperature range in which the resistance value of the CO sensor 13 is maintained approximately constant during a predetermined incomplete combustion is connected to the circuit connected to the temperature switch 2.
0 was connected as an intervention.

In the figure, 21, 22, 23, 24, 25 are resistors for current adjustment, 26 is a capacitor that prevents malfunction of the incomplete combustion detection circuit 10 in response to abnormal pulse generation of CO gas, 27 is an NPN type transistor,
28 and 29 are PNP transistors, and 30 is a diode.

Next, the operation of the illustrated embodiment will be explained.

In this case, the incomplete combustion circuit 10 is activated and the electromagnetic safety valve 1 is closed when the CO concentration in the combustion exhaust reaches 500 PPM as shown in Fig. 2. ,
Within the combustion exhaust temperature range where the resistance value of the CO sensor 13 is maintained at approximately 150Ω when the CO concentration is 500 PPM, in other words, the temperature on the surface of the CO sensor 13 is 100°C.
The one that closes within the range of 130°C was used.

First, with the temperature switch 20 set, when the burner 2 is ignited and the main switch 11 is closed, the CO sensor 13 is held at a high resistance value, and the potential at the voltage dividing point D of the voltage divider 15 is set to a relatively low VV. ₁ , so the two transistors 1
7 and 18 are both turned on, and the capacitor 9 of the latching relay 5 is charged by the battery 12, and during a short period of time when the charging current flows, the setting relay 7 is turned on.
is energized, its contact 5a closes, and a drive circuit 6 for the electromagnetic safety valve 1 is formed. Since the burner 2 is burning at this time, the thermocouple 4 is connected to the burner 2.
The burner 2 is heated to generate a predetermined electromotive force, and a current sufficient to keep the electromagnetic safety valve 1 open can be passed through the operating solenoid 1a, so that the burner 2 continues to burn.

When the CO concentration reaches an abnormal value of 500 PPM or more during combustion in the burner 2, the thermocouple 4 is heated and generates a predetermined electromotive force, but for example, the gas pressure supplied to the burner 2 is When the temperature of the combustion exhaust gas is within the normal temperature range and the heating temperature of the CO sensor 13 is in the range of 100°C to 130°C, the resistance value of the CO sensor 13 is a low resistance of 200Ω or less. value, and the potential at the voltage dividing point D of the voltage divider 10 changes to relatively high _V2 , so both transistors 17 and 18 are turned off, and the reset relay 8 is energized, its contact 5a opens, and the thermoelectric The energization of the actuating solenoid 1a by the pair 4 is cut off, the electromagnetic safety valve 1 is closed, and the combustion of the burner 2 is stopped, making it safe.

However, even if the CO concentration reaches an abnormal value of 500 PPM or more, for example, the gas pressure supplied to the burner 2 exceeds the standard pressure, the temperature of the combustion exhaust exceeds the normal temperature range, and the heating temperature of the CO sensor 13 increases. When the temperature reaches about 150°C, the resistance value of the CO sensor 13 changes only to about 300Ω, and it no longer becomes 200Ω or less like when the gas pressure is within the standard pressure, and the voltage divider 10 Since the potential at the pressure point D is lower than _V2 , without the temperature switch 20, both transistors 17 and 18 would remain on, making it impossible to correctly detect the incomplete combustion state.However, in the present invention, incomplete combustion detection The circuit 10 includes a temperature switch 20 that closes within a combustion exhaust temperature range in which the resistance value of the incomplete combustion detection element is held approximately constant during a predetermined incomplete combustion (here, when the CO concentration reaches 500 PPM or more). Since the temperature of the combustion exhaust exceeds the normal temperature range, the temperature switch 20 is opened, the latching relay 5 is reset, and the thermocouple 4 is connected to the operating solenoid 1a. The power supply is immediately cut off, the electromagnetic safety valve 1 is closed, and combustion in the burner 2 is stopped, making it safe.

Furthermore, when the burner 2 is in a combustion stopped state or a misfire state, the thermocouple 4 is not heated and the operating solenoid 1a is not energized, so the electromagnetic safety valve 1 is maintained in the closed state and there is no gas leakage, which is safe. It is.

It is also possible to replace the latching relay in the above embodiment with a general relay.

(Effects of the Invention) According to the present invention, the incomplete combustion detection circuit closes within the combustion exhaust temperature range in which the resistance value of the incomplete combustion detection element is held substantially constant during a predetermined incomplete combustion. Since the temperature switch is connected as an intervention, the temperature switch can close the electromagnetic safety valve even outside the combustion exhaust temperature range where the incomplete combustion detection element cannot accurately detect incomplete combustion, increasing the reliability of the incomplete combustion detection circuit. It has the effect of further improving sex.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one example of implementing the device of the present invention. FIG. 2 is a characteristic diagram showing the relationship between the CO concentration, the surface temperature of the CO sensor, and the resistance value. 1... Solenoid safety valve, 1a... Operating solenoid,
2... Burner, 3... Gas supply path (fuel supply path),
4...Thermocouple (thermoelectric element), 6... Drive circuit, 1
0...Incomplete combustion detection circuit, 13...CO sensor (incomplete combustion detection element), 20...Temperature switch.

Claims (1)

[Claims] 1. An electromagnetic safety valve installed in the fuel supply path to the burner, a drive circuit for the electromagnetic safety valve that connects the operating solenoid of the electromagnetic safety valve to a thermoelectric element, and a CO sensor heated by combustion exhaust and other incomplete combustion detection devices. and an incomplete combustion detection circuit that closes the electromagnetic safety valve when a gas concentration equal to or higher than a set value is detected by the element, the incomplete combustion detection circuit detects that the incomplete combustion occurs at a predetermined incomplete combustion. A combustion safety device characterized by intervening and connecting a temperature switch that closes within a combustion exhaust temperature range in which the resistance value of a combustion detection element is maintained substantially constant.