JPH0587337A - Preventing device of no-water burning of gas burning apparatus - Google Patents

Abstract

PURPOSE:To stop supply of gas when a water flow is absent and thereby to prevent no-water burning by providing a signal modifying means which always puts a signal to a safety means in a state of non-detection of flame irrespective of a signal from a flame detecting means in a state of non-detection of the water flow. CONSTITUTION:When a failure such as short circuit or disconnection occurs in the vicinity of a signal intake part from a water flow detecting means 1 to a control means 2 and the control means 2 judges a signal from the water flow detecting means 1 to be in a state of detection of the water flow though no water flow passes through a heat exchanger 15, the control means 2 makes a valve driving device 3 operate to open a solenoid operated valve device 22, thereby gas is supplied to a gas burner 20 and burning is started. In this state, however, a signal modifying means 6 puts a signal for a safety device 5 in a state of non-detection of flame irrespective of a signal from a flame detecting means 4. When a prescribed time passes, accordingly, the valve driving device 3 stops operation, the solenoid operated valve device 22 is closed and supply of the gas to the gas burner 20 is stopped. Thereby no-water burning can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for preventing emptying of gas combustion equipment, such as an instantaneous water heater or a circulating bath heater, which controls combustion by water flow.

[0002]

2. Description of the Related Art In this type of gas combustion equipment, a signal from a water flow sensor for detecting a water flow passing through a heat exchanger is input to a combustion control device and gas is supplied to a gas burner when the water flow sensor detects no water flow. Stop to prevent water heating. Microcomputers are often used for this type of combustion control device, but if a failure such as a short circuit or disconnection occurs near the signal acquisition part of the water flow sensor, there will be no water flow through the heat exchanger. Nevertheless, the combustion control device may determine that the signal from the water flow sensor is in the water flow detection state, operate the gas burner, and perform empty heating.

In order to solve such a problem, in the technique disclosed in Japanese Patent Publication No. 1-51714, a valve opening / closing command signal is given to a fuel valve control circuit based on a flow rate signal from a flow rate detection circuit. In addition to the main control circuit, a flow rate monitoring circuit that operates by the flow rate signal from the same flow rate detection circuit is provided, and if the flow rate falls below the minimum allowable flow rate, the flow rate monitoring circuit changes from the flow rate monitoring circuit to the fuel valve control circuit The valve closing command signal is directly given to prevent the water heating even when the main control circuit fails.

[0004]

However, the technique disclosed in Japanese Patent Publication No. 1-51714 requires a comparator or the like in the flow rate monitoring circuit, which complicates the structure and increases the manufacturing cost. .. An object of the present invention is to prevent empty heating with a simple structure by using a safety device that normally stops the gas supply when a combustion flame of a gas burner normally provided in this type of gas combustion equipment is not detected. ..

[0005]

To this end, the apparatus for preventing dry heating of a gas combustion apparatus according to the present invention is provided in a gas supply pipe 21 to a gas burner 20 for heating a heat exchanger 15, as shown in FIG. Solenoid valve device 22, a valve drive device 3 for operating the solenoid valve device, a water flow detection means 1 for detecting a water flow passing through the heat exchanger 15, and a signal from the water flow detection means is in a water flow detection state. Sometimes the valve drive device 3
Is operated to control the amount of gas supplied to the gas burner 20 via the solenoid valve device 22, a flame detection unit 4 for detecting combustion flame of the gas burner 20, and a signal from the flame detection unit. In the gas combustion apparatus comprising the safety means 5 for stopping the valve drive device 3 and stopping the gas supply to the gas burner 20 after a lapse of a predetermined short time in the flame non-detection state, the flame detection means 4 to the safety means 5 separately from the control means 2, when the signal from the water flow detection means 1 is in the water flow detection state, the signal from the flame detection means 4 is directly used as the safety means. 5. When the water flow is not detected, the signal correction means 6 is provided for keeping the signal to the safety means 5 always in the flame non-detection state regardless of the signal from the flame detection means 4. thing A.

[0006]

In a normal operating state, if the water flow detecting means 1 detects the water flow passing through the heat exchanger 15, the control means 2 operates the valve driving device 3 to open the solenoid valve device 22 to open the gas burner 20.
The gas is supplied to start combustion. If the signal from the flame detection means 4 is in the flame detection state, the safety means 5 operates the valve drive device 3
If the flame is not detected, the operation of the valve drive device 3 is stopped, the electromagnetic valve device 22 is closed, and the gas supply to the gas burner 20 is stopped.

A signal from the water flow detection means 1 is transmitted even though there is no water flow through the heat exchanger 15 due to a failure such as a short circuit or disconnection in the vicinity of the signal intake portion from the water flow detection means 1 to the control means 2. When the control means 2 determines that it is in the detection state, the control means 2 operates the valve drive device 3 to open the electromagnetic valve device 22 and supply gas to the gas burner 20 to start combustion. However, in this state, the signal correction means 6 sets the signal sent to the safety means 5 to the flame non-detection state irrespective of the signal from the flame detection means 4, so that the valve drive device 3 will operate after a predetermined short time. When stopped, the solenoid valve device 22 is closed and the gas supply to the gas burner 20 is stopped.

[0008]

As described above, according to the present invention, the control means malfunctions due to a failure of the signal intake part from the water flow detection means, and the gas burner burns even though there is no water flow in the heat exchanger. Even after starting, the gas supply to the gas burner is stopped after a lapse of a predetermined short time, and the combustion is stopped, so that the empty heating is prevented. Further, since the gas supply to the gas burner is stopped by using the safety means originally possessed by the combustion control device, the structure required for preventing the water heating becomes simple, and the manufacturing cost is only slightly increased.

[0009]

The present invention will be described below with reference to the embodiment shown in FIG. As shown in FIG. 2, a gas burner 20 is provided in the lower part of the case 10 forming the combustion chamber of the instantaneous water heater, and fuel gas is supplied by a gas supply pipe 21 having an electromagnetic valve device 22. Combustion air is supplied by an electric fan 23 provided on the lower side. The solenoid valve device 22 is the original solenoid valve 2 arranged in series from the gas supply source side.
2a, a proportional solenoid valve 22c and a main solenoid valve 22b, the original solenoid valve 22a and the main solenoid valve 22b are solenoid valves that only open and close, and the proportional solenoid valve 22c has a continuous opening according to a control current. This is a solenoid valve that changes to change the gas supply amount to the gas burner 20. Further, the electric fan 23 continuously changes the rotation speed and supplies the combustion air in an amount corresponding to the gas supply amount.

A water supply pipe 1 connected to an inlet side of a once-through type heat exchanger 15 provided in a case 10 above a gas burner 20.
6, a water flow sensor 31 is provided, and a hot water supply pipe 17 connected to the outlet side is provided with a hot water temperature sensor 32 and a hot water tap 18. The water supplied from the water supply pipe 16 is heated by the gas burner 20 when passing through the heat exchanger 15, reaches a predetermined temperature, and is discharged from the hot water tap 18. The upper part of the case 10 above the heat exchanger 15 passes through the hood 11 and the exhaust pipe 1
2 connected to the case 10 just above the gas burner 20
A flame sensor 30 such as a frame rod is provided inside.

The electronic control unit 40 for controlling the operation of the instant water heater is composed of a central processing unit (CPU), a read only memory (ROM), a writable memory (RAM) and an interface. An operation unit 41 provided with necessary various switches, a hot water temperature setting device, various display lamps, etc. is connected. Further, the electronic control unit 40 is connected to each solenoid valve 22 via valve drive circuits 42a, 42b, 42c.
a, 22b, 22c, the electric fan 23 via the motor drive circuit 43, and the flame sensor 30 via the flame detection circuit 44.
However, the hot water temperature sensor 32 is connected via the temperature detection circuit 45. The valve drive circuits 42a, 42b, 42c are connected to the solenoid valves 22a, 2b according to the output signal from the electronic control unit 40.
The valve drive device 3 that controls the gas supply to the gas burner 20 by controlling the opening degrees of 2b and 22c is configured. Flame sensor 30
If the flame detection circuit 44 detects the combustion flame of the gas burner 20, the output signal to the port 40b of the electronic control unit 40 is set to the flame detection state of a predetermined voltage, and if the combustion flame is not detected, the 0 voltage flame non-detection state is set. The flame detecting means 4 is configured. The flame detecting means 4 is not limited to one using a frame rod as in the embodiment, but any one using a thermocouple or the like can be used.

The detection switch 31a of the water flow sensor 31 is
It is normally off, but it is turned on when the amount of water passing through the heat exchanger 15 exceeds a predetermined minimum allowable flow rate, one terminal is grounded, and the other terminal is connected via a resistor to the DC power supply terminal 47. Is connected to the port 40a of the electronic control unit 40. This water flow sensor 31 detects the water flow passing through the heat exchanger 15 and sets the output signal to the electronic control unit 40 to the water flow detection state of 0 voltage when the detection switch 31a is turned on, and the water flow amount is a predetermined minimum allowable flow rate. The water flow detecting means 1 is configured to bring the water flow into a non-detection state of a predetermined voltage when the power is turned off in the following cases. The water flow detecting means 1 is not limited to the switch type as in the embodiment, but any combination such as a combination of a pulse generating type flow rate sensor and a flow rate detecting circuit can be used.

The base of a transistor 46 is connected to the other terminal of the detection switch 31a through a resistor, the emitter of the transistor 46 is grounded, and the collector is connected to the electronic control unit 40 side of the flame detection circuit 44. There is.
The collector and the emitter of the transistor 46 are cut off when the detection switch 31a is on, and are connected to each other when the detection switch 31a is off. This transistor 46 connected between the flame detection circuit 44 and the port 40b of the electronic control unit 40.
Is cut off when the water flow sensor 31 detects the water flow, and the signal from the flame detection circuit 44 is directly transmitted to the electronic control unit 4
When the water flow sensor 31 does not detect the water flow, the signal is transmitted from the flame detection circuit 44 regardless of the presence or absence of the combustion flame of the gas burner 20. The signal correction means 6 for transmitting to the. The signal correcting means 6 is not limited to the one using a transistor as in the embodiment, but various kinds can be used according to the type of the water flow detecting means 1.

First, the normal operation of this embodiment will be described. When the hot water tap 18 is closed, the detection switch 31a of the water flow sensor 31 is off. Therefore, the port 40a of the electronic control unit 40 receives a water flow non-detection signal of a predetermined voltage from the DC power supply terminal 47, and the transistor 46 is turned on. ing. In this state, the electronic control unit 40 has the original solenoid valve 22a.
Also, the main solenoid valve 22b is closed, the proportional solenoid valve 22c is set to the minimum opening degree, the gas is not supplied to the gas burner 20, and the instantaneous water heater is not operated.

When the hot water tap 18 is opened and the amount of water passing through the heat exchanger 15 exceeds a predetermined minimum allowable flow rate, the water flow sensor 31.
Since the detection switch 31a of 1 is turned on, the water flow detection signal of 0 voltage is input to the port 40a of the electronic control unit 40, and the transistor 46 is cut off. In this state in which the water flow detection signal has been input, the electronic control unit 40 sets the original solenoid valve 2
2a and the main solenoid valve 22b are opened, gas is supplied to the gas burner 20 and ignited by an ignition device (not shown), and the electric fan 23 is operated to operate the instantaneous water heater. The flame sensor 30 such as a flame rod detects the combustion flame of the gas burner 20, and the flame detection circuit 44 causes the electronic control unit 40 to operate.
If a flame detection signal of a predetermined voltage is input to the port 40b of the electronic control unit 40, the electronic controller 40 continues the operation of the instantaneous water heater,
The hot water temperature detected by the hot water temperature sensor 32 is compared with the temperature set by the water flow sensor 31, and the opening degree of the proportional solenoid valve 22c is controlled so that the hot water temperature becomes the set temperature, thereby supplying gas to the gas burner 20. The amount of combustion air is controlled by controlling the amount of the air and the rotational speed of the electric fan 23 accordingly. However, for some reason the gas burner 20
If no combustion flame is detected, a flame non-detection signal of voltage 0 is input from the flame detection circuit 44 to the port 40b of the electronic control unit 40, and the safety means 5 constituted by a part of the electronic control unit 40 operates. , After the lapse of a predetermined short time, the original solenoid valve 22
a and the main solenoid valve 22b are closed, the proportional solenoid valve 22c is set to the minimum opening degree, the gas supply to the gas burner 20 is stopped, and the operation of the instantaneous water heater is stopped.

When a failure such as a short circuit or a disconnection occurs near the port 40a of the electronic control unit 40, and the voltage of the port 40a becomes 0 even though the detection switch 31a is off, the water flow through the heat exchanger 15 is generated. Despite not being
It is erroneously determined that there is this water flow, the original solenoid valve 22a and the main solenoid valve 22b are opened, gas is supplied to the gas burner 20 and the ignition device ignites to start the operation of the instantaneous water heater.
However, in this state, since the transistor 46 provided separately from the electronic control unit 40 is conducting, even if the combustion flame of the gas burner 20 is detected by the flame sensor 30 and the flame detection circuit 44, the voltage of the port 40b of the electronic control unit 40 is reduced. Is 0, that is, the flame non-detection signal is input. Therefore, the safety means 5 constituted by a part of the electronic control unit 40 operates, and after a predetermined short time has passed, the original solenoid valve 22a and the main solenoid valve 22b are closed, and the proportional solenoid valve 22c is set to the minimum opening degree to the gas burner 20. Stop the gas supply and stop the operation of the instant water heater.

As described above, according to this embodiment, the electronic control unit 40 malfunctions due to a failure in the vicinity of the port 40a or the like, and the gas burner 20 receives gas even though there is no water flow through the heat exchanger 15. Even if the gas is supplied to start the combustion, the gas supply to the gas burner 20 is stopped after the elapse of a predetermined short time, and the combustion is stopped, so that the empty heating is prevented. Also,
Since the gas supply to the gas burner 20 is stopped by using the safety means 5 originally provided in the electronic control unit 40, one transistor and two resistors are sufficient for the parts necessary for preventing the empty heating, and the wiring is required. Since the structure including is also simple, a slight increase in manufacturing cost is sufficient.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an empty heating prevention device for a gas combustion device according to the present invention.

FIG. 2 is an overall structural diagram of an embodiment of an empty heating prevention apparatus for a gas combustion device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Water flow detection means, 2 ... Control means, 3 ... Valve drive device, 4
... Flame detecting means, 5 ... Safety means, 6 ... Signal correcting means, 15
... heat exchanger, 20 ... gas burner, 21 ... gas supply pipe, 2
2 ... Solenoid valve device.

Claims (1)

[Claims] 1. A solenoid valve device provided in a gas supply pipe to a gas burner for heating a heat exchanger, a valve drive device for operating the solenoid valve device, and a water flow detection means for detecting a water flow passing through the heat exchanger. When the signal from the water flow detection means is in the water flow detection state, the valve drive device is operated to control the gas supply amount to the gas burner via the electromagnetic valve device, and the combustion flame of the gas burner. A flame detecting means for detecting, and a safety means for stopping the valve driving device and stopping the gas supply to the gas burner after a predetermined short time when the signal from the flame detecting means is in the flame non-detecting state. In the gas combustion equipment provided, when the signal from the water flow detecting means is in the water flow detecting state in the signal transmission path from the flame detecting means to the safety means, separately from the control means. The signal from the flame detection means is transmitted to the safety means as it is, but when the water flow is not detected, the signal correction means is always provided to keep the signal to the safety means independent of the signal from the flame detection means. An apparatus for preventing emptying of gas combustion equipment, which is characterized by being provided.