JPH0220612Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a combustion control device for a water heater in which combustion is controlled by the operation of a water flow detection switch.

Generally, in this type of device, when there is abnormal combustion or misfire, or when the combustion circuit itself becomes abnormal, the abnormality detection circuit detects this abnormal state and automatically operates the combustion circuit. It is known that the heating of the water is stopped, thereby stopping the heating of the water. However, in conventional devices of this type, in order to restart combustion after the operation of the combustion circuit has temporarily stopped due to an abnormality detection signal from the abnormality detection circuit, a reset switch provided separately must be operated to restart the operation of the combustion circuit. There was the inconvenience of having to restart the system or open and close the power switch.

This idea was made in view of the above circumstances, and includes a combustion circuit that controls combustion operation, an abnormality detection circuit that detects abnormality in combustion operation, a pair of power input terminals to which power is supplied, and one A water flow detection switch whose contact is connected to one terminal of the power input terminal and is closed upon detecting the flow of water, and the other contact of the water flow detection switch is connected to one power supply terminal of the combustion circuit. circuit opening/closing means comprising a transistor inserted in series in at least one of a power supply line connecting the other terminal of the power supply input terminal and the other power supply terminal of the combustion circuit; When power is supplied from the other contact of the water flow detection switch and the other terminal of the power input terminal and the abnormality detection circuit outputs an abnormality detection signal, the circuit opening/closing means is opened and this open state is maintained. and opening/closing control means constituted by a thyristor.

Below, an embodiment of this invention will be explained with reference to the drawings. Fig. 1 is a diagram showing an example of a water heater applied to this invention, in which city gas, propane gas, gas , a water heater 2 having a burner for heating water with a fluid fuel such as kerosene or heavy oil is provided, and the pipe 1
A water stop valve 3 such as a faucet is provided at the terminal.
Further, a water flow detection switch 4 is provided near the water stop valve 3 to detect the flow of water. This water flow detection switch 4 is normally open, and when water flows (when the water stop valve 3 is opened)
It suffices if the switch is configured to close when
Any device can be used, such as a differential pressure switch that operates by detecting differential pressure.

Next, FIG. 2 is a circuit diagram showing the configuration of a combustion control device for a water heater, which is an embodiment of this invention.
In this figure, 5a and 5b are power input terminals to which power (DC power) for this device is supplied, the power input terminal 5a being the positive side and the power input terminal 5b being the negative side. Between the power input terminal 5a and one power terminal 6a of the combustion circuit 6 that controls the combustion of the water heater 2, the water flow detection switch 4 and the NPN transistor 7, which is a circuit opening/closing means, are connected in series. It is interposed. Further, the power input terminal 5b is directly connected to the other power supply terminal 6b of the combustion circuit 6. A resistor 8 and a thyristor 9 are sequentially inserted in series between the contact on the transistor 7 side of the water flow detection switch 4 and the power input terminal 5b, and a Zener diode 10 is inserted in parallel with the thyristor 9. There is. Further, the gate of the thyristor 9 is connected to an abnormality detection signal output terminal of an abnormality detection circuit 11 that detects when the combustion operation of the water heater 2 becomes abnormal (for example, a misfire occurs) or when the combustion circuit 6 becomes abnormal. 11a, and the anode of this thyristor 9 is connected to the base of transistor 7. In this case, resistor 8, thyristor 9,
The Zener diode 10 is connected to the transistor 7
It constitutes an opening/closing control means 12 that controls the conduction state of the circuit, that is, the opening/closing state of the circuit. Note that the configurations of the combustion circuit 6 and the abnormality detection circuit 11 are similar to those known in the art, and therefore will not be described in detail here.

In this embodiment configured as described above, when the water stop valve 3 of a faucet or the like is opened, water flows through the pipe 1, which activates the water flow detection switch 4, and the contact point of this water flow detection switch 4 is activated. Closed. In this state, since no abnormality detection signal is applied to the thyristor 9, a base current corresponding to the Zener voltage of the Zener diode 10 is supplied to the base of the transistor 7 via the resistor 8, and the transistor 7 becomes conductive. As a result, power is supplied to the combustion circuit 6, and the combustion circuit 6 becomes operational, so that the water heater 2 starts combustion. Here, if the water heater 2 burns abnormally or misfires, or if an abnormal state occurs in the combustion circuit 4, the abnormality detection circuit 11 detects this abnormality and generates an abnormality detection signal, and sends this signal to the thyristor. Supply to gate 9. As a result, the thyristor 9 becomes conductive and maintains this conductive state by itself, so that the base current of the transistor 7 is no longer supplied and the transistor 7 becomes non-conductive. Therefore, power is no longer supplied to the combustion circuit 6, and the operation of the combustion circuit 6 is stopped, so that combustion is stopped. After that, if the water stop valve 3 of a faucet or the like is closed to stop the flow of water in the conduit 1, the contact of the water flow detection switch 4 is opened, thereby eliminating the input voltage applied to the thyristor 9, and the thyristor 9 becomes self-maintaining. The condition is cleared.
Next, when the water stop valve 3 of a faucet or the like is opened to allow water to flow into the pipe 1, the contact of the water flow detection switch 4 is closed, and therefore the combustion circuit 6 becomes operational as described above and combustion resumes. be done. Therefore, when it is desired to restart combustion after combustion has stopped due to various abnormalities, once the water stop valve 3 such as a faucet is closed and then opened again, combustion will be automatically restarted.

In addition, in this embodiment described above,
Although a DC power source is used as the power source, it is also possible to configure this as an AC power source, and it is of course also possible to configure the circuit opening/closing means using a relay circuit.

As is clear from the above description, the combustion control device for a water heater according to this invention is configured such that power for the combustion circuit is supplied through the water flow detection switch and the circuit opening/closing means in series, and The circuit opening/closing means is opened in response to an abnormality detection signal from the abnormality detection circuit and maintained in the open state, so that when combustion stops due to abnormal combustion, misfire, or an abnormality in the combustion circuit itself, the circuit opening/closing means opens the faucet, etc. Combustion can be restarted by once closing the water shut-off valve and then opening it, eliminating the need for a separate reset switch unlike conventional devices, and eliminating the need to operate a separate reset switch or power switch. Therefore, the effect of eliminating the complexity of restarting operations when combustion is stopped can be obtained. Further, in the present application, since the circuit opening/closing means and the opening/closing control means are each composed of a transistor and a thyristor,
It has the advantages of reliable operation, excellent durability, and extremely high reliability.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a water heater to which this invention is applied, and FIG. 2 is a circuit diagram showing the construction of an embodiment of this invention. 4...Water flow detection switch, 5a, 5b...Power input terminal, 6...Combustion circuit, 6a, 6b...Power terminal, 7...Circuit opening/closing means (transistor), 9
...Thyristor, 11...Abnormality detection circuit, 12...
...Opening/closing control means.

Claims (1)

[Scope of utility model registration request] a combustion circuit for controlling combustion operation, an abnormality detection circuit for detecting abnormality in combustion operation, a pair of power input terminals to which power is supplied, one contact being connected to one of the power input terminals; A water flow detection switch that is closed upon detecting the flow of water, and a power supply system connecting the other contact of the water flow detection switch and one power terminal of the combustion circuit or the other terminal of the power input terminal. and the other power input terminal of the combustion circuit; and opening/closing control means constituted by a thyristor that opens the circuit opening/closing means when power is supplied from the other terminal and the abnormality detection circuit outputs an abnormality detection signal, and maintains this open state. A combustion control device for a water heater characterized by: