JPH0450006B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a temperature control device for electric water heaters used in general households.

Conventional configuration and its problems A conventional temperature control device for an electric water heater has a circuit configuration as shown in FIG. In the figure, 1
is an AC power supply, 2 is a high-power first heater, 3 is a thermostat connected to the first heater 2, and 4 is a low-power second heater connected in parallel to the first heater 2.
The heater 5 is a temperature switch connected to the second heater 4.

The operation of the electric water heater configured as above will be described below. First, when the water temperature in the container is low, for example around 27 degrees Celsius (normal temperature), the thermostat 3 and the temperature switch 5 are in the on state, and the first heater 2 and the second heater 4 are energized. This causes the water temperature in the water heater to rise. Generally, thermostat 3 is set to operate (off) at around 90℃, and the water temperature is
When the temperature exceeds 90° C., the first heater 2 is no longer energized, and the second heater 4 with low power continues heating. The temperature switch 5 is set to operate at about 93°C, and is turned off when the water temperature exceeds 93°C and turned on when the water temperature falls below 93°C. Therefore, if the water temperature in the container exceeds 90°C, then if the water temperature is below 93°C, the second heater 4 is energized to heat the water, and if it exceeds 93°C, the second heater 4 The heater 4 is no longer energized and heating of the water is stopped. That is, the water temperature is controlled at around 93° C. by turning the temperature switch 5 on and off.

Here, the set temperature of the temperature switch 5 has variations considering mass production, and the boiling temperature of water also changes depending on the environment such as atmospheric pressure. That is, because the set temperature of the temperature switch 5 varies widely and the boiling temperature of water is lowered due to the influence of atmospheric pressure, the set temperature of the temperature switch 5 may become higher than the boiling temperature of water in some cases. be. In this case, since the temperature switch 5 is not turned off, the heater 4 continues to be energized, which may lead to a very dangerous situation. Therefore, in order to prevent the dangerous situation described above from occurring, the set temperature of the temperature switch 5 must be set low, generally around 93°C.

Due to these constraints, the temperature of the hot water obtained in conventional electric water heaters is mostly determined by the set temperature of the temperature switch 5, and is usually around 93℃, which is very low compared to the boiling temperature of 100℃. The problem is that only low-temperature hot water can be obtained, which is too low to be used for hot water tea, especially coffee and tea.

Purpose of the Invention The present invention solves the above conventional problems, and aims to realize an electric water heater with a simple configuration that can always provide hot water close to boiling temperature. be.

Structure of the Invention In order to achieve the above object, a temperature control device for an electric water heater of the present invention includes a heater that heats water in a container, and a current control means that controls the current of this heater. A prism provided in the path of bubbles generated when water boils, a phototransistor that receives light from a light emitting diode through the prism, and a control means that controls the current control means based on the output of the phototransistor. According to this configuration, the boiling state is detected by the bubbles generated when water boils, regardless of environmental changes such as atmospheric pressure, so the water temperature is always controlled to a high temperature close to boiling temperature. It is something that can be done.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. In FIG. 2, 6 is a heater, and 7 is a current control means such as a bidirectional three-terminal thyristor (hereinafter referred to as a TRIACK) or a relay for controlling the current of the heater 6. An embodiment using a TRIACK will be described below. Reference numeral 8 denotes a bubble detecting means configured to detect bubbles generated when water in a container boils using reflected light from a prism.This bubble detecting means 8 is constituted by parts 9 to 14 shown below. That is, 9 is a light emitting diode, 10 is a pair with light emitting diode 9, and light emitting diode 9
A phototransistor installed together with the phototransistor, 11,1
2 is a light emitting diode 9 and a phototransistor 10
resistors 13 and 14 for current limiting;
13 is a resistor, and 14 is an electrolytic capacitor. Reference numeral 15 denotes a gate control means configured to control the gate of the triax 7 based on the output of the bubble detection means 8, and this gate control means 15 is composed of parts 16 to 21 shown below. 16 is a buffer for inputting and amplifying the output of the bubble detection means 8; 17 and 18 are resistors for dividing the output of the buffer 16; and 19 is turned on by the output of the buffer 16.
Transistor to be turned off, 20 is transistor 1
a current control resistor for controlling the collector current of 9;
1 is a resistor that allows a gate current to flow through the gate of the triac 7 based on the output of the transistor 19.

FIG. 3 shows the structure of the bubble detection means 8, with a showing a top view and b showing a side view. In this figure, 9 is a light emitting diode, 10 is a phototransistor, 22 is a prism, and this prism 2
2 is made of transparent acrylic resin in the shape of a pentagonal prism, and is configured so that the light from the light emitting diode 9 passes through the interior thereof, and is placed near the bottom of the container of the electric water heater, and its tip The portion faces a bubble passageway (not shown) within the container.

Regarding the electric water heater configured as above,
The operation will be explained below.

First, when the tip of the prism 22 is underwater,
The reflectance of light on the A and B surfaces of the prism 22 is small, so most of the light emitted from the light emitting diode 9 is transmitted in the direction α, and as a result, the phototransistor 10 receives almost no light. Therefore, the area between the collector and emitter of the phototransistor 10 remains off.
Further, when the prism 22 is in the air, the reflectance of light on the A side and the B side of the prism is large, so that most of the light emitted from the light emitting diode 9 travels in the direction β. As a result, the phototransistor 10 receives light, and the portion between the collector and emitter of the phototransistor 10 is turned on.

Now, if there is water in the container of the electric water heater and the temperature of this water is sufficiently lower than the boiling temperature, the tip of the prism 22 will be in the water, so the light emitting diode 9 will turn off according to the principle described above. No light is input to phototransistor 10, and phototransistor 10 remains off. Therefore, the potential of the emitter of the phototransistor 10 is 0V,
Moreover, the voltage across the electrolytic capacitor 14 is also 0V, and as a result, the output of the bubble detection means 8 is 0V. Therefore, the output of the buffer 16 also becomes 0V.
No base current flows to transistor 19, and transistor 19 is turned off. As a result, a current flows between the resistor 20, the resistor 21, the gate and the cathode of the triax 7, the triax 7 is triggered, and the heater 6 is energized. When this heater 6 is energized, the water temperature in the container rises.

When the temperature of the water in the container rises due to heating by the heater 6 and the water boils, a large amount of bubbles will be generated from the bottom of the container. The bubbles make the tip of the prism appear as if it were placed in the air instead of in water. According to the principle described above, the light from the light emitting diode 9 is input to the phototransistor 10, which turns on. . As a result, the electrolytic capacitor 14 is charged via the resistor 13, and the voltage across the electrolytic capacitor 14 increases. The output of the bubble detection means 8 is buffer 16
When the threshold voltage of
The output is Hi voltage (saturation voltage almost close to +Vcc)
Output. A current flows to the base of the transistor 19 via the resistor 17, and the transistor 19 is turned on. Therefore, the output of the gate control means 15 becomes 0, no current flows through the gate of the triac 7, the triac 7 is turned off, and the heater 6 is no longer energized.

Further, when the heater 6 is no longer energized, the temperature of the boiling water in the container decreases, and the bubbles that have been generated disappear. When these bubbles stop forming,
The phototransistor 10 is turned off, the electrolytic capacitor 14 is no longer charged, and the resistors 13,
It is discharged through the resistor 12. When the voltage across the electrolytic capacitor 14 drops below the threshold voltage of the buffer 16, the output of the buffer 16 becomes
It becomes 0V. As a result, the triax 7 is energized in the same manner as described above, the hot water in the container is heated again, and the same operation as described above is repeated thereafter. That is, according to the embodiment shown in FIG. 2, the water once boiled is maintained near the boiling temperature by turning the triax 7 on and off.

In this case, since the boiling temperature is detected based on the state of bubble generation, the boiling temperature is not controlled at a low temperature as in the conventional example shown in FIG. 1, but almost at the boiling temperature. Furthermore, when the water heater container runs out of water and is empty, the tip of the prism 22 is in the air inside the container, and no electricity is applied to the heater 6, which prevents water boiling. It is.

Effects of the Invention As is clear from the above embodiments, the temperature control device for an electric water heater of the present invention includes a prism provided in the path of bubbles generated when water in a container is boiled, and a light emitting diode connected to the prism through the prism. The thermostat is equipped with a phototransistor that receives light from the thermostat, and a control means that controls the current control means based on the output of this phototransistor.With this configuration, temperature fluctuations, which are unavoidable during mass production of thermostats, are installed. Temperature control for electric water heaters that eliminates the need to consider variations in settings, and that constantly controls the water temperature at boiling temperature to provide high-temperature hot water, regardless of environmental changes such as changes in air pressure during use. The device can be obtained with a simple configuration, and therefore has an excellent effect of being able to brew hot water tea, coffee, black tea, etc. with good flavor.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional temperature control device for an electric water heater, FIG. 2 is a circuit diagram of a temperature control device for an electric water heater according to an embodiment of the present invention, and FIG. 3 is a configuration of a bubble detection means. In the figures, a is a plan view and b is a side view. 6... Heater, 7... Current control means, 8... Bubble detection means, 9... Light emitting diode, 10... Photo transistor, 15... Control means, 22...
prism.

Claims (1)

[Claims] 1.Equipped with a heater that heats the water in the container and a current control means that controls the current of this heater, and a prism provided in the path of bubbles generated when the water in the container boils, and A temperature control device for an electric water heater, comprising a phototransistor that receives light from a light emitting diode, and a control means that controls the current control means based on the output of the phototransistor.