JPS6345812B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electric water heater that heats water to produce hot water.

Conventional structure and its problems Conventionally, in this type of electric water heater, the container for storing water is formed into a vessel shape from a material such as stainless steel, and a heating element is wrapped around the lower side of the water heater. Water in a container was heated, a temperature controller was attached to the bottom of the container, and the temperature controller and the heating element were connected in series. Furthermore, since the operating temperature of the temperature controller is set at 93 to 98°C, it requires a highly accurate one, making it expensive. Moreover,
Even with such a temperature controller, the water will not reach the boiling point, and the sterilization in the water will be insufficient.
The drawback was that it did not remove the limescale from the tap water, making it impossible to make delicious tea or coffee.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks.
It is an object of the present invention to provide an electric water heater that can reliably detect when water in a container reaches a boiling point.

Structure of the Invention In order to achieve the above object, the electric water heater of the present invention comprises: a container containing a liquid; a heating element provided at the bottom of the container to heat the liquid; and a heating element located near the heating element. a first temperature-sensing element attached to the container, a second temperature-sensing element attached to a sensing part provided by protruding a part of the bottom of the container downward; and the first temperature-sensing element. a detection device that outputs a detection signal when a difference between the temperature of the first temperature sensing element and the temperature of the second temperature sensing element becomes a predetermined value or less when the temperature of the element is higher than a predetermined temperature; switch, and an energizing device that starts operating according to the operating switch, stops operating in response to a detection signal from the detecting device, and stops energizing the heating element. The system detects when the water in the container has reached the boiling point, convection becomes intense, and the temperature of the water in the container is even.This ensures that the water is boiled, and as a result, the water is sufficiently sterilized. It also removes limescale from tap water, allowing you to make delicious tea or coffee.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a container, and the container 1 is made of a material such as stainless steel and has a heater 2 wrapped around its lower side, and a temperature regulator 3 is attached to the lower part of the container 1. It is connected in series with the heater 2. 4 is located above the heater 2 and the container 1
The first thermistor is mounted on the wall of
This second thermistor 5 is attached to a sensing portion 6 provided by protruding a portion of the bottom surface of the container 1 downward.

FIG. 2 shows a circuit diagram, and as shown in this circuit diagram, a heater 2 and a temperature regulator 3 are connected in series and connected to a commercial power source 7. Further, a diode 8, a resistor 9, and a capacitor 10 are connected in series and connected to a commercial power supply 7, and a series circuit of a low resistance resistor 11 and a Zener diode 12 is connected in parallel to the capacitor 10, and a power supply 13 of the control circuit is connected. and outputs direct current between the terminals of the Zener diode 12. Further, a series circuit of the first thermistor 4 and a resistor 14, a series circuit of the second thermistor 5 and a resistor 15, and a series circuit of low resistors 16 and 17 are connected in parallel to the Zener diode 12, respectively. 18 and 19 are open collector output comparators, and the first thermistor 4
The divided voltage between the low resistor 14 and the comparator 18 +
side input and the − side input of the comparator 19, and connect the divided voltage of the second thermistor 5 and the low resistor 15 to the − side input of the co-comparator 18,
Further, the voltage divided by the resistor 16 and the low resistor 17 is connected to the + side input of the comparator 19. Further, the outputs of the comparators 18 and 19 are connected to the cathode of the Zener diode 12 via a low resistor, and further connected to one end of a low resistor 22 via diodes 20 and 21, and the other end of the low resistor 22 is connected to a transistor. It is connected to the base of 23. Then, a diode 24, a resistor 25 and a capacitor 2
6 are connected in series and connected to the commercial power supply 7, and the Zener diode 27 is connected to the capacitor 2.
6 in parallel to form a power source 29 for driving the relay coil 28. Also, relay coil 2
One end of the relay coil 28 is connected to the collector of the transistor 23, the other end of the relay coil 28 is connected to the cathode of the Zener diode 27, and the emitter of the transistor 23 is connected to the anode of the Zener diode 27. 30 is relay coil 2
This diode 30 is connected in parallel to the relay coil 28 and prevents generation of a back electromotive voltage in the relay coil 28. An operating switch 31 is connected between the collector and emitter of the transistor 23. 32 is a relay contact, and this relay contact 32 has a common/normally closed terminal connected between the base and emitter of the transistor 23, and a common/normally open terminal connected to the temperature controller 3 in parallel. 3
3 is a stop switch, and this stop switch 33 is connected between the base and emitter of the transistor 23.

In the above configuration and circuit diagram, the operation will be explained based on FIG. 3. When water is placed in the container 1 and electricity is applied, current flows to the heater 2 via the temperature controller 3, heating the water in the container 1 and increasing the temperature of the water.
When the temperature reaches 93 to 98°C, the temperature regulator 3 repeats opening and closing to keep the water temperature constant. At this time, when the contact of the operating switch 31 is closed in a pulsed manner, current flows through the relay coil 28, and the common and normally open terminals of the relay contact 32 are short-circuited. At the same time, since the temperature of the first thermistor 4 is low, the output of the comparator 19 is turned OFF, and as a result, the output of the comparator 1
Transistor 23 regardless of the output of 8.
In order to turn on the relay coil 28, current continues to flow through the relay coil 28 even after the contact of the operating switch 31 is opened.
This is because when the water temperature is low, there is no difference in temperature between the first and second thermistors 4 and 5, so when the water temperature is low, the heater 2 is energized by the output of the comparator 19. Since the first thermistor 4 is located above the heater 2 and attached to the wall of the container 1, the temperature rises almost following the water temperature. However, the second
The thermistor 5 is attached to a sensing part 6 that projects downward from a part of the bottom of the container 1, so when the water temperature is low, there is little water convection, so the water temperature is low compared to the water temperature. As the temperature increases and approaches the boiling point, water convection becomes more intense and rapidly follows the water temperature. When the water temperature reaches 80°C, the output of the comparator 19 turns ON, but at this time, the output of the comparator 18 turns OFF because the temperature difference between the first and second thermistors 4 and 5 is large.
The heater 2 continues to be energized. By the time the water starts to boil, the convection becomes intense and the second thermistor 5
When the temperature of the first thermistor 4 rises rapidly and approaches the temperature of the first thermistor 4, the output of the comparator 18 is inverted and turned ON, so the transistor 23 is turned OFF and the connection between the common and normally closed terminals of the relay contact 32 is turned off. A short circuit occurs, and power supply to the heater 2 is stopped. In this way, boiling is detected. By the way, when boiling is detected, boiling can be stopped at any time by shorting the stop switch 33.

In this embodiment, discrete components are used, but it can also be easily configured using a microcomputer.

Effects of the Invention As is clear from the above explanation, according to the electric water heater of the present invention, the water in the container reaches the boiling point, convection becomes intense, and the temperature of the water in the container becomes even. As a result, the water can be reliably boiled, and the boiling can be detected automatically.As a result, the water can be sufficiently sterilized, and limescale etc. in the tap water can be removed, making delicious tea possible. or coffee.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of an electric water heater showing an embodiment of the present invention, FIG. 2 is a circuit diagram of the water heater, and FIG. 3 is an explanatory diagram of its operation. DESCRIPTION OF SYMBOLS 1... Container, 2... Heater, 4... First thermistor, 5... Second thermistor, 6... Sensing section, 18, 19... Comparator, 28... Relay coil, 32... Relay contact.

Claims (1)

[Claims] 1. A container containing a liquid, a heating element provided at the bottom of the container to heat the liquid, a first temperature sensing element located near the heating element and attached to the container, When the temperature of the second temperature-sensing element attached to the sensing part, which is provided with a part of the bottom protruding downward, and the first temperature-sensing element exceeds a predetermined temperature, this first temperature-sensing element The temperature of the element and the second
a detection device that outputs a detection signal when the difference in temperature between the temperature sensing elements of the sensor becomes less than a predetermined value; and an activation switch, the activation switch starts the operation and the detection signal of the detection device stops the operation. An electric water heater comprising: an energizing device that stops energizing the heating element.