JPH02219950A - Controller device for hot water feeder - Google Patents

Abstract

PURPOSE:To provide a hot water feeder having a less-expensive and safe water- less heating prevention device by a method wherein a temperature sensor circuit, a differential circuit, a water level sensing circuit, a relay driving element triggered by an output from the differential circuit and a relay for use in controlling a heater device are provided in an electrical series-connected state. CONSTITUTION:A detecting temperature of a thermistor 13 is lowered, a voltage at an output terminal of a comparator 19 is increased, a + voltage is applied to a coil 36 of a relay, a transistor 27 and a transistor 30 are turned ON by a voltage charged in a capacitor 26, the voltage is supplied to a comparator 36 and a voltage is supplied to an electrode 32. At this time, if there is no water within a tank 1, a water resistance is approximately limitless, a voltage at an inverting input terminal of the comparator 36 is high, a voltage at the output terminal of the comparator 36 is not increased more than the voltage at a non-inverting input terminal of the comparator 36 and a gate current of a thyristor 41 is not flowed, resulting in that the thyristor 41 is kept OFF, the coil 39 of the relay is not energized and a heater 11 is not heated.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a control device for a water heater.

In conventional water heaters, water is poured into a tank, heated by a heating device, and heated to a preset temperature by a temperature detection means attached to the tank to detect the temperature of the water. The structure is as follows. However, if the heating device is operated with no water in the tank, not only will the tank be abnormally heated, but there is also the risk of fatal damage to the functionality of the water heater. Therefore, in order to prevent such a situation from occurring, such water heaters are equipped with a dry heating prevention device.

The dry firing prevention device, as shown in Fig. 4, constantly flows current from an electrode 4 attached to the tank 1 through water to the metal part of the tank 1, and connects the electrode 46, transistor 46, transistor 47, etc. shown in Fig. 5. The presence or absence of water is detected by the current detection circuit configured by , and if the state where the current stops flowing is detected, there is a risk of dry heating, so the relay coil 64 is de-energized and the heating device 8 is prevented from operating. It has become.

Problems to be Solved by the Invention However, in such a device, since a current is constantly passed through the electrode 4, the electrode 8i4 wears out due to a migration phenomenon, so it is necessary to plate a hard metal with an even harder metal on the surface. Requires something expensive. In addition, there were many other problems, such as scale adhesion to metal parts in the tank 1, which has a low potential compared to the potential of the electrode 4, and gas generated by electrolysis.

The present invention provides a water heater control device that solves the above problems.

Means for Solving the Problems In order to solve the above problems, the water heater control device of the present invention detects the presence or absence of water in the tank using a small current in an extremely short period of time when the heating device of the water heater starts operating. detect,
The heating device starts operating if there is water, and stops operating if there is no water and there is a risk of dry heating.

Effect: Although the above configuration is almost the same as a conventional water heater, it is extremely inexpensive and does not require the use of special materials, and it is safe to prevent dry heating without worrying about scale adhesion or gas generation. It is possible to provide a water heater having the device.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

Fig. 4 shows the configuration of a water heater using the control device of the present invention. In Fig. 4, 1 is a tank, 2 is a hot water supply port disposed at the top of the tank 1, 3 is a control surface, and 4 is a tank l. 5 is a temperature sensor for detecting the temperature of the water in tank 1; 6 is a water supply port provided at the bottom of tank 1; 7 is a drain port; 8 is a heating means for heating the water in the tank 1. 2 and 1 show electrical circuit diagrams of the control circuit of the present invention. 9 in Figure 2
10 is an AC power source, and 10 is a contact point of a relay that opens and closes the current of a heater, which is a heating means. In FIG. 1, when the temperature detected by thermistor 13 decreases, the voltage at the inverting input terminal of comparator 19, which is supplied with a divided voltage by thermistor 13 and resistor 15, decreases, and
, the voltage at the output terminal of comparator 19 rises to the voltage divided by resistors 18, 20 and 21, turning on transistor 25 and at the same time turning on the capacitor. 26 and simultaneously turns on the transistor 27. When the transistor 25 is turned on, the transistor 24 is also turned on, and ten voltages are applied to the coil 39 of the relay. On the other hand, the transistor 27 similarly turns on the transistor 30 and supplies power to the comparator 36 and at the same time supplies voltage to the electrode 32 via the resistor 31. As shown in FIG. 1, the electrode 32 is placed in contact with the water in the tank 1, so if there is water, the voltage divided by the resistor 31 and the resistance of the water in the tank will be When the voltage at the non-inverting input terminal of the comparator 36 is lowered by the resistance of the resistor 36 and is supplied to the inverting input terminal of the comparator 36, the voltage at the output terminal of the comparator 36 becomes lower than the voltage at the non-inverting input terminal of the comparator 36, which is supplied by the resistor 34 and the resistor 35.
7 and 38, the gate current of the thyristor 41, which is a relay driving element, flows, and the thyristor 41 becomes ONE.The relay coil 39 is energized, and the relay contact 10 in FIG. 2 turns ON. The heater 11 is heated.

On the other hand, the transistor 27 is turned ON by the charging voltage of the capacitor 26, but as the charging voltage is discharged by the resistor 23, the transistor 27 becomes 0FFI again. At the same time, the voltage supply to the electrode 32 via the resistor 31 is also stopped.The voltage supply to the resistor 37 is also stopped.As a result, the voltage at the output terminal of the comparator 36 decreases, and the voltage at the output terminal of the comparator 36 is reduced. Thyristor 41
game)・The current stops flowing, but the Sai IJ star 41 is O.
N state is maintained, the relay coil 39 is energized, and the second
The relay contact 10 in the figure is also ON and continues.

Next, when the temperature detected by the thermistor 13 rises, the voltage at the inverting input terminal of the comparator 19, which is supplied with a divided voltage by the thermistor 13 and the resistor 15, increases and decreases by 2, turning the transistor 25 OFF and turning the transistor 24 OFF at the same time.
F, the voltage supply to the relay coil 39 is stopped, and the relay contact 10 in FIG. 2 is turned OFF! , heating of the heater 1 is stopped. At this time, the transistor 27 remains OFF because no operating voltage is supplied to it. Next, the temperature detected by the thermistor 13 decreases again, and the voltage at the output terminal of the comparator 19 increases, turning on the transistors 25 and 24, and turning on the relay coil 36.
At the same time, the voltage charged in the capacitor 26 causes the transistors 27 and 3 to
0 is turned ON, power is supplied to the comparator 36, and at the same time, voltage is supplied to the electrode 32 via the resistor 31. At this time, if there is no water in the tank 1, the resistance of the water becomes almost infinite, and the voltage at the inverting input terminal of the comparator 36 supplied via the resistor 31 is high. The voltage at the output terminal of the comparator 36 does not rise due to the voltage at the non-inverting input terminal of , and the gate current of the thyristor 41 does not flow, so the thyristor 41 remains OFF and the coil 39 of the relay is not excited. The heater 11 is not heated, that is, when there is no water in the tank due to the dry firing prevention device, the heater 11 does not start energizing even if the temperature inside the tank drops. Furthermore, once this dry-heating prevention device detects dry-heating as described above, it automatically returns to normal and does not re-energize even if water is supplied into the tank. To re-energize, turn on the return switch 29 provided to short-circuit both ends of the resistor 15! ,,
By lowering the voltage at the inverting input terminal of the comparator 19, the temperature detected by the thermistor 13 is lowered and the temperature is returned to the state when the power is re-energized, thereby making it possible to recover from the dry firing detection state.

FIG. 3 shows an embodiment of the dry firing prevention device of the present invention in which the voltage applied to the electrode and tank is insulated and separated from the voltage of the control circuit in order to protect the circuit from malfunctioning from various electromagnetic interferences. It is.

In the explanation of FIG. 3, since the AC circuit section is similar, it will be explained at the same time as FIG. 2. In the figure, as the temperature detected by the thermistor 68 decreases, the voltage at the output terminal of the comparator 74 increases, transistors 80 and 79 are turned on, and 10 voltage is applied to the coil 92 of the relay, and at the same time, the voltage charged in the capacitor 81 is increased. by transistor 8
2 and transistor 85 are turned on, supplying power to comparator 89 and at the same time supplying voltage to the light receiving side of photocoupler 105 via resistor 86. The DC amount a! connected to the thermistor 68, etc. A separate DC flow l! which is insulated and separated from X67. Since the electrode 98 connected to the circuit 196 is arranged so as to be in contact with the water in the tank 1 as shown in FIG.
7 and the resistance of the water in the tank is borrowed by the resistance of the water, transistor 101 is turned on, and transistor 106 is also turned on, supplying voltage to the light receiving side of photocoupler 105, and the light receiving side Turn on the transistor. As a result, the voltage at the inverting input terminal of the comparator 89, which is supplied via the resistor 87, decreases and becomes lower than the voltage at the non-inverting input terminal of the comparator 89, which is supplied by the resistors 87 and 88, and the voltage at the output terminal of the comparator 89 decreases. The voltage increases, and the gate current of the thyristor 94, which is the relay driving element, flows and the thyristor 9
4 is turned ON, the relay coil 92 is energized, the relay contact 10 in FIG. 2 is ONL, and the heater 11 is heated. On the other hand, the transistor 82 is turned on by the charging voltage of the capacitor 81, but as the charging voltage is discharged by the resistor 78, the transistor 85 is turned off again. The voltage supplied to the light receiving side of the photocoupler 105 is stopped through the photocoupler 105. Further, the voltage supply to the resistor 90 is also stopped. As a result, the voltage at the output terminal of the comparator 89 decreases, and the gate current of the thyristor 94, which is a 1/- drive element, stops flowing, but the thyristor 94 remains in the ON state, and the relay coil 92 is energized, as shown in FIG. Relay contact 10 also remains ON.

Next, when the temperature detected by the thermistor 68 increases, the voltage at the inverting input terminal of the comparator 74, which is supplied with a partial voltage by the thermistor 68 and the resistor 70, increases, and
9 and resistor 71, the voltage at the output terminal of comparator 74 decreases, turning transistor 80 off.
At the same time, the transistor 79t+turns OFF, the voltage supply to the coil 92 of the relay is stopped, and the relay contact lO in FIG. 2 is turned OFF, and heating of the heater 11 is stopped. At this time, the transistor 82 is turned OFF because no operating voltage is supplied to it! .

There is a lot.

Next, the temperature detected by the thermistor 68 falls again, and the voltage at the output terminal of the comparator 74 rises, turning on the transistors 80 and 79, and applying a voltage to the relay coil 92, at the same time charging the capacitor 81. The voltage turns on the transistor 82 and the transistor 85, supplying power to the comparator 89 and at the same time supplying voltage to the light receiving side of the photocoupler 105 via the resistor 86. At that time, if there is no water in the tank 1, the resistance of the water becomes almost infinite and the transistor 101 is turned off, and the transistor 106 is also turned off, so no current flows to the light emitting side of the photocoupler 105, and the light receiving side transistor is turned off. become. Then, the voltage at the inverting input terminal of the comparator 89 becomes high and exceeds the voltage at the non-inverting input terminal of the comparator 89 supplied by the resistors 87 and 88, so that the voltage at the output terminal of the comparator 89 does not rise and the voltage at the thyristor 94 increases. Since the gate current does not flow, the thyristor 94 remains OFF and the relay coil 92 is not energized, and the heater 11 shown in Fig. 2 is not heated. Even if the temperature drops, the heater does not start energizing. Furthermore, once this dry-heating prevention device detects dry-heating as described above, it automatically returns to normal and does not re-energize even if water is supplied into the tank. To re-energize, turn on the return switch 84 provided to short-circuit both ends of the resistor 70 and lower the voltage at the inverting input terminal of the comparator 74, thereby lowering the temperature detected by the thermistor 68 and re-energizing. By changing the state to this state, it is possible to recover from the dry heating detection state. In addition to the method according to the two embodiments described above, the operation of preventing dry firing described above also exhibits the same operation and effect when executed by a program such as a microcomputer.

Effects of the Invention As described above, according to the present invention, the presence or absence of water in the tank is detected in an extremely short time and with a small current when the heating device of the water heater starts operation, and if water is present, the operation is started. If there is a risk of dry heating due to lack of water, the operation of the heating device is stopped, which causes the electrodes to wear out due to a migration phenomenon due to the continuous current flow, which was a problem with conventional dry heating prevention devices. Therefore, it requires expensive materials such as plating the surface of a highly hard metal with an even more hard metal. It also solves many problems such as scale adhesion to metal parts in the tank, which has a low potential compared to the potential of the electrodes, and gas generation due to electrolysis. Therefore, it is possible to provide a water heater having a safe dry heating prevention device that does not require the use of special materials, is extremely inexpensive, and has no fear of scale adhesion or gas generation.

[Brief explanation of the drawing]

1st rJ! J is a circuit diagram of a DC power supply section according to an embodiment of the water heater control device of the present invention, FIG. 2 is a circuit diagram of an AC IT power supply section according to the present invention and a conventional water heater control device, and FIG. A DC' @ power supply circuit diagram of the second embodiment using the water heater control J device, Fig. 4 is a block diagram of a water heater using the present invention and a conventional water heater control @ system, and Fig. 5 is a conventional water heater control circuit diagram. The circuit diagram of the DC power supply section of the water heater control device is shown. ■・・・Tank, 2...Hot water inlet, 3...
...Control surface, 4...Electrode, 6...
Water supply port, 7...Drain port, 8...Heating device, 9...AC power supply, 12...DC power supply, 13... Thermistor, 19...
Comparator, 26... Capacitor, 28...
...transistor, 41...thyristor. Name of agent: Patent attorney Shigetaka Awano Haka1ra-・-
Poomisg/9-11 Konnozu Radar 2B-゛Transisg

Claims (1)

[Claims] In a water heater that has a hot water inlet at the top, a water inlet and a drain at the bottom, a heating device for heating the water in the tank, and an electrode placed in contact with the water, the electric a temperature detection circuit arranged in series with the differential circuit,
A control device for a water heater, comprising a water detection circuit, a relay driving element triggered by the output thereof, and a relay for controlling the heating device.